@article{veazie_chen_hicks_holley_eylands_mattson_boldt_brewer_lopez_whipker_2024, title={A Data-driven Approach for Generating Leaf Tissue Nutrient Interpretation Ranges for Greenhouse Lettuce}, volume={59}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI17582-23}, abstractNote={In the absence of controlled sufficiency studies, foliar interpretations for many horticultural crops are based on survey concentrations from small data sets. In addition, both survey and sufficiency ranges provide little interpretation regarding zones that are above or below the concentration range deemed “sufficient.” While providing a critical initial set of ranges, it was based on a limited set of data and therefore improvements in interpretation of data are needed. This study presents a novel method based on 1950 data points to create data-driven nutrient interpretation ranges by fitting models to provide more refined ranges of deficient (lowest 2.5%), low (2.5% to 25%), sufficient (25% to 75%), high (75% to 97.5%), and excessive (highest 2.5%). Data were analyzed by fitting Normal, Gamma, and Weibull distributions. Corresponding P values were calculated based on the Shapiro-Wilk test for normality for the Normal and Gamma distributions, and the Kolmogorov-Smirnov test was used for the Weibull distribution. The optimal distribution was selected based on the lowest Bayesian Information Criterion (BIC) value and visual fitness. The Weibull distribution best represented nitrogen, phosphorus, potassium, calcium, manganese, zinc, and copper, and the Gamma distribution best represented magnesium, sulfur, iron, and boron. Using the selected distributions, we propose a refined set of nutrient evaluation ranges for greenhouse-grown lettuce. These refined standards will aid growers and technical specialists in more accurately interpreting leaf tissue sample data.}, number={3}, journal={HORTSCIENCE}, author={Veazie, Patrick and Chen, Hsuan and Hicks, Kristin and Holley, Jake and Eylands, Nathan and Mattson, Neil and Boldt, Jennifer and Brewer, Devin and Lopez, Roberto and Whipker, Brian E.}, year={2024}, month={Mar}, pages={267–277} }
 @article{whipker_veazie_ballance_hicks_owen_rich_seltsam_cockson_2024, title={Coleus cultivars nutritional status as a function of leaf coloration}, ISSN={["1532-4087"]}, DOI={10.1080/01904167.2024.2325939}, journal={JOURNAL OF PLANT NUTRITION}, author={Whipker, Brian and Veazie, Patrick and Ballance, M. Seth and Hicks, Kristin and Owen, W. Garrett and Rich, W. Tyler and Seltsam, Lauren and Cockson, Paul}, year={2024}, month={Mar} }
 @article{veazie_jeong_jackson_suchoff_whipker_2024, title={Peat Substrates Amended with Wood-based Biochar Do Not Influence the Efficacy of Paclobutrazol Drenches}, volume={59}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI17621-23}, abstractNote={Various soilless substrate components have been evaluated for many years to identify sustainable resources that do not negatively impact plant growth. Biochar is a carbon-based material that has been evaluated for use as an alternative aggregate in peat-based soilless substrates. In addition, the use of carbon adsorption for compound removal is widely used in groundwater remediation, municipal water filtration, and volatile organic compounds. Experiment one aimed to determine the impact of coarse biochar (<6 mm) on paclobutrazol efficacy when incorporated at 15% or 30% by volume in a peat-based substrate when compared with a perlite-amended substrate at the same incorporation volumes. In Expt. 1, a single paclobutrazol drench application of 0, 0.5, 1.0, 2.0, and 4.0 mg·L−1 was applied to ‘Princettia Red’ and ‘Princettia White’ poinsettias (Euphorbia pulcherrima × Euphorbia cornastra). In Expt. 2, two different biochar particle sizes of coarse (<6 mm) and extra coarse (>6 mm) were examined at the same incorporation volumes as Expt. 1 and compared with a perlite-amended substrate at the same incorporation volumes. However, during Expt. 2, continual drench applications at times of irrigation of 0.0, 6.25, 12.5, 25.0, 50, and 100 μg·L−1 (ppb) paclobutrazol were applied to pansy (Viola ×wittrockiana) ‘Matrix Blue Blotch’ and begonia (Begonia ×hybrida) ‘Big Red Bronze Leaf’. The efficacy of paclobutrazol drenches for controlling growth in all species was unaffected by the substrate composition regarding aggregate type or aggregate incorporation rate. Thus, even though biochar is often used for bioremediation and wastewater treatment, it did not negatively impact the efficacy of paclobutrazol drenches at the concentrations used. This research suggests that when biochar is used as an amendment to peatmoss it will not influence paclobutrazol drench efficacy when incorporated up to 30% by volume for the examined species.}, number={2}, journal={HORTSCIENCE}, author={Veazie, Patrick and Jeong, Ka Yeon and Jackson, Brian and Suchoff, David and Whipker, Brian E.}, year={2024}, month={Feb}, pages={248–254} }
 @article{veazie_balance_whipker_jeong_2023, title={Comparison of Peat-Perlite-based and Peat-Biochar-based Substrates with Varying Rates of Calcium Silicate on Growth and Cannabinoid Production of <i>Cannabis sativa</i> 'BaOx'}, volume={58}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI17324-23}, abstractNote={Growers have been searching for alternative horticultural growing media components because of their desire to use sustainable resources. Biochar is a carbon-based material that has been evaluated for use as an alternative aggregate in peat-based soilless substrates. Additionally, silicon (Si) has been examined as a beneficial element to promote plant growth and plant quality in a variety of crops. However, there has been limited research regarding the interaction of biochar as an aggregate and Si in soilless substrates. This study aimed to determine the impact of Si and biochar on plant growth and nutrient uptake for greenhouse-cultivated hemp (Cannabis sativa L.). Hemp plants were grown in one of 12 different substrate blends: with two rates of calcium silicate (CaSiO3), two aggregate types of biochar (medium or coarse) or perlite, and aggregate percentages of 85% peat + 15% aggregate and 70% peat + 30% aggregate. The cannabinoid concentration, plant height, diameter, or total plant biomass were similar across all substrate blends after 12 weeks of growth. Additionally, the use of CaSiO3 as a Si substrate amendment increased Si foliar concentrations, and the addition of biochar to peat-based mixes did not limit the Si availability for plant uptake. However, Si substrate amendments did not impact plant height, diameter, or total plant biomass. This suggests that the biochar tested during this study is suitable in peat-based substrates for C. sativa ‘BaOx’ production at rates up to 30% (by volume) in peat-based substrates with CaSiO3 amendments.}, number={10}, journal={HORTSCIENCE}, author={Veazie, Patrick and Balance, M. Seth and Whipker, Brian E. and Jeong, Ka Yeon}, year={2023}, month={Oct}, pages={1250–1256} }
 @article{james_vann_suchoff_mcginnis_whipker_edmisten_gatiboni_2023, title={Hemp yield and cannabinoid concentrations under variable nitrogen and potassium fertilizer rates}, volume={4}, ISSN={["1435-0653"]}, url={https://doi.org/10.1002/csc2.20966}, DOI={10.1002/csc2.20966}, abstractNote={Abstract}, journal={CROP SCIENCE}, author={James, Maggie S. and Vann, Matthew C. and Suchoff, David H. and McGinnis, Michelle and Whipker, Brian E. and Edmisten, Keith L. and Gatiboni, Luciano C.}, year={2023}, month={Apr} }
 @article{pandey_veazie_whipker_young_2023, title={Predicting foliar nutrient concentrations and nutrient deficiencies of hydroponic lettuce using hyperspectral imaging}, volume={230}, ISSN={["1537-5129"]}, DOI={10.1016/j.biosystemseng.2023.05.005}, abstractNote={Effective management of plant essential nutrients is necessary for hydroponically grown lettuce to achieve high yields and maintain production. This study investigated in situ hyperspectral imaging of hydroponic lettuce for predicting nutrient concentrations and identifying nutrient deficiencies for: nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), and sulphur (S). A greenhouse study was conducted using ‘Salanova Green’ lettuce grown with controlled solution treatments with varying macronutrient fertility rates of 0, 8, 16, 32, 64, and 100% each for N, P, K, Ca, Mg, and S. Plants were imaged using a hyperspectral line scanner at six and eight weeks after transplanting; then, plant tissues were sampled, and nutrient concentrations measured. Partial least squares regression (PLSR) models were developed to predict nutrient concentrations for each nutrient individually (PLS1) and for all six nutrient concentrations (PLS2). Several binary classification models were also developed to predict nutrient deficiencies. The PLS1 and PLS2 models predicted nutrient concentrations with Coefficient of Determination (R2) values from 0.60 to 0.88 for N, P, K, and S, while results for Ca and Mg yielded R2 values of 0.12–0.34, for both harvest dates. Similarly, plants deficient in N, P, K, and S were classified more accurately compared to plants deficient in Ca and Mg for both harvest dates, with F1 values (F-scores) ranging from 0.71 to 1.00, with the exception of K which had F1 scores of 0.40–0.67. Overall, results indicate that both leaf tissue nutrient concentration and nutrient deficiencies can be predicted using hyperspectral data collected for whole plants.}, journal={BIOSYSTEMS ENGINEERING}, author={Pandey, Piyush and Veazie, Patrick and Whipker, Brian and Young, Sierra}, year={2023}, month={Jun}, pages={458–469} }
 @article{henry_veazie_furman_vann_whipker_2023, title={Spectral Discrimination of Macronutrient Deficiencies in Greenhouse Grown Flue-Cured Tobacco}, volume={12}, ISSN={["2223-7747"]}, DOI={10.3390/plants12020280}, abstractNote={Remote sensing of nutrient disorders has become more common in recent years. Most research has considered one or two nutrient disorders and few studies have sought to distinguish among multiple macronutrient deficiencies. This study was conducted to provide a baseline spectral characterization of macronutrient deficiencies in flue-cured tobacco (Nicotiana tabacum L.). Reflectance measurements were obtained from greenhouse-grown nutrient-deficient plants at several stages of development. Feature selection methods including information entropy and first and second derivatives were used to identify wavelengths useful for discriminating among these deficiencies. Detected variability was primarily within wavelengths in the visible spectrum, while near-infrared and shortwave-infrared radiation contributed little to the observed variability. Principal component analysis was used to reduce data dimensionality and the selected components were used to develop linear discriminant analysis models to classify the symptoms. Classification models for young, intermediate, and mature plants had overall accuracies of 92%, 82%, and 75%, respectively, when using 10 principal components. Nitrogen, sulfur, and magnesium deficiencies exhibited greater classification accuracies, while phosphorus and potassium deficiencies demonstrated poor or inconsistent results. This study demonstrates that spectral analysis of flue-cured tobacco is a promising methodology to improve current scouting methods.}, number={2}, journal={PLANTS-BASEL}, author={Henry, Josh and Veazie, Patrick and Furman, Marschall and Vann, Matthew and Whipker, Brian}, year={2023}, month={Jan} }
 @article{veazie_ballance_whipker_2023, title={Supplemental lighting spectrum impact on sweet potato cutting production and rooting}, volume={9}, ISSN={["2374-3832"]}, DOI={10.1002/cft2.20202}, abstractNote={Abstract}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Veazie, Patrick and Ballance, M. Seth and Whipker, Brian}, year={2023}, month={Jun} }
 @article{veazie_jeong_ballance_whipker_2023, title={The Use of Silicon Substrate Amendments to Decrease Micronutrient Concentrations at Varying Micronutrient Fertility Rates with Cannabis sativa 'Auto CBG'}, volume={58}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI17162-23}, abstractNote={Many abiotic factors impact the yield and growth of Cannabis sativa (cannabis). Cannabis has been reported to be a bio-accumulator of heavy metals. For growers who are targeting floral production and other byproducts for human consumption, this is a concern. Silicon (Si) has been examined as a beneficial plant element to limit the uptake of heavy metals in a variety of crops. The objective of this study was to determine the impact of Si on heavy metal micronutrient uptake and plant growth for greenhouse-cultivated cannabis at varying Si substrate amendments. ‘Auto CBG’ plants were grown in a 70:30 peat:perlite substrate with one of three varying calcium silicate (CaSiO3) (Si) substrate amendment rates, Si0X, Si0.5X, or Si1X (of 0.0, 1.04, and 2.07 kg⋅m−3 CaSiO3), and one of three micronutrient fertility treatments, M1X [0.49 boron (B), 0.19 copper (Cu), 4.02 iron (Fe), 0.99 manganese (Mn), 0.01 molybdenum (Mo), and 0.20 zinc (Zn) mg⋅L−1], M2X, or M4X, using a modified Hoagland’s solution, creating a 3 × 3 factorial. Plants grown with a Si1X substrate amendment exhibited a significantly lower iron concentration in the foliage and root tissue when compared with those grown in a substrate without Si. After 6 weeks of growth, Si0X plants that received a M4X fertility rate exhibited greater foliar micronutrient concentrations of B, Mn, Zn, Fe, and Cu than plants that received a Si substrate amendment when provided a M4X fertility rate. Additionally, lower micronutrient concentrations in floral tissue were observed in plants that received a Si substrate amendment for M2X and M4X when compared with plants that did not. Silicon substrate amendments had no impact on the cannabinoid concentration or plant growth metrics after 12 weeks of growth. This research suggests that using a Si substrate amendment in a greenhouse production system can limit excessive uptake and accumulation of micronutrients in the foliage, roots, and floral material of cannabis without negative impacts on plant growth or cannabinoid concentrations.}, number={7}, journal={HORTSCIENCE}, author={Veazie, Patrick and Jeong, Ka Yeon and Ballance, M. Seth and Whipker, Brian E.}, year={2023}, month={Jul}, pages={797–803} }
 @article{lu_young_linder_whipker_suchoff_2022, title={Hyperspectral Imaging With Machine Learning to Differentiate Cultivars, Growth Stages, Flowers, and Leaves of Industrial Hemp (Cannabis sativa L.)}, volume={12}, ISSN={["1664-462X"]}, DOI={10.3389/fpls.2021.810113}, abstractNote={As an emerging cash crop, industrial hemp (Cannabis sativa L.) grown for cannabidiol (CBD) has spurred a surge of interest in the United States. Cultivar selection and harvest timing are important to produce CBD hemp profitably and avoid economic loss resulting from the tetrahydrocannabinol (THC) concentration in the crop exceeding regulatory limits. Hence there is a need for differentiating CBD hemp cultivars and growth stages to aid in cultivar and genotype selection and optimization of harvest timing. Current methods that rely on visual assessment of plant phenotypes and chemical procedures are limited because of its subjective and destructive nature. In this study, hyperspectral imaging was proposed as a novel, objective, and non-destructive method for differentiating hemp cultivars, growth stages as well as plant organs (leaves and flowers). Five cultivars of CBD hemp were grown greenhouse conditions and leaves and flowers were sampled at five growth stages 2–10 weeks in 2-week intervals after flower initiation and scanned by a benchtop hyperspectral imaging system in the spectral range of 400–1000 nm. The acquired images were subjected to image processing procedures to extract the spectra of hemp samples. The spectral profiles and scatter plots of principal component analysis of the spectral data revealed a certain degree of separation between hemp cultivars, growth stages, and plant organs. Machine learning based on regularized linear discriminant analysis achieved the accuracy of up to 99.6% in differentiating the five hemp cultivars. Plant organ and growth stage need to be factored into model development for hemp cultivar classification. The classification models achieved 100% accuracy in differentiating the five growth stages and two plant organs. This study demonstrates the effectiveness of hyperspectral imaging for differentiating cultivars, growth stages and plant organs of CBD hemp, which is a potentially useful tool for growers and breeders of CBD hemp.}, journal={FRONTIERS IN PLANT SCIENCE}, author={Lu, Yuzhen and Young, Sierra and Linder, Eric and Whipker, Brian and Suchoff, David}, year={2022}, month={Feb} }
 @article{veazie_pandey_young_ballance_hicks_whipker_2022, title={Impact of Macronutrient Fertility on Mineral Uptake and Growth of Lactuca sativa 'Salanova Green' in a Hydroponic System}, volume={8}, ISSN={["2311-7524"]}, url={https://doi.org/10.3390/horticulturae8111075}, DOI={10.3390/horticulturae8111075}, abstractNote={Lactuca sativa (commonly referred to as lettuce) is one of the most popular grown hydroponic crops. While other fertilizer rate work has been conducted on lettuce, the impact of each element has not been evaluated independently or by determining adequate foliar tissue concentrations when all nutrients are plant-available. This study explores the impact that macronutrients have on the growth and yield of lettuce at different stages of the production cycle. Additionally, this study explores the adequate nutrient rates by regressing nutrient curves to find the concentration of each element that corresponds to optimal growth. Plants were grown under varying macronutrient concentrations (0, 8, 16, 32, 64, and 100%) utilizing the concentrations of a modified Hoagland’s solution based on 150 mg·L−1 N. Lettuce plants were grown in a silica sand culture and received a nutrient solution in which a single element was altered. Visual symptomology was documented, and leaf tissue mineral nutrient concentrations and biomass were measured at Weeks 3, 6, and 8 after transplant. Optimal elemental leaf tissue concentration and biomass varied by macronutrient rates and weeks of growth. Nitrogen rate produced a linear increase in total plant dry weight, but foliar N followed a quadratic plateau pattern. Other elements, such as phosphorus, potassium, and magnesium, produced distinct total plant dry weight plateaus despite increasing fertility concentrations. These results demonstrate that fertility recommendation can be lowered for nutrients where higher rates do not result in higher plant biomass or foliar nutrient concentrations.}, number={11}, journal={HORTICULTURAE}, author={Veazie, Patrick and Pandey, Piyush and Young, Sierra and Ballance, M. Seth and Hicks, Kristin and Whipker, Brian}, year={2022}, month={Nov} }
 @article{cockson_whipker_2021, title={Characterization of nutrient disorders of ornamental Brassica oleracea 'Red Bor'}, volume={1305}, ISSN={["2406-6168"]}, DOI={10.17660/ActaHortic.2021.1305.55}, journal={III INTERNATIONAL SYMPOSIUM ON GROWING MEDIA, COMPOSTING AND SUBSTRATE ANALYSIS}, author={Cockson, P. and Whipker, B. E.}, year={2021}, pages={423–430} }
 @article{landis_hicks_mccall_henry_whipker_2021, title={Customizing the leaf tissue nutrient ranges for blue and pink hydrangeas}, ISSN={["1532-4087"]}, DOI={10.1080/01904167.2021.1952431}, abstractNote={Abstract Pink, blue, and red hydrangea [(Hydrangea macrophylla subsp. Macrophylla var. macrophylla (Thunb.)] cultivars contain the anthocyanin pigment delphinidin-3-glucoside that color the sepal. Without aluminum (Al), the natural color of the pigment is pink or red depending on the cultivar. To produce blue sepals, plants are fertilized with Al2(SO4)3 (AS) under low phosphorus (P) conditions. To determine the effect of AS on nutrient tissue concentrations ‘Early Blue’, ‘Hor Tivoli’, ‘Jip’, and ‘Mathilda Gutges’ plants were treated with 0 (pink), 12, or 15 g (blue) of AS. Pre-bloom leaf tissue concentrations were analyzed with blue cultivars generally having higher concentrations of sulfur (S), iron (Fe), manganese (Mn), zinc (Zn), boron (B), copper (Cu), and Al, while the pink plants had higher nitrogen (N), P, calcium (Ca), and magnesium (Mg) concentrations. Concentrations of N, potassium (K), Mg, B and Cu were consistent with published sufficiency ranges regardless of color or cultivar, while S, Fe, Mn and Zn concentrations were below sufficiency in some pink cultivars. The P concentrations in both pink and blue cultivars and Ca in some blue cultivars were lower than the published sufficiency range. The difference in leaf tissue nutrient concentrations among cultivars and coloration, suggest that nutrient uptake in hydrangeas varies and that lab recommendations should be customized depending on cultivar and color production system.}, journal={JOURNAL OF PLANT NUTRITION}, author={Landis, Hunter and Hicks, Kristin and McCall, Ingram and Henry, Josh B. and Whipker, Brian E.}, year={2021}, month={Jul} }
 @article{landis_hicks_mccall_henry_whipker_2021, title={Enhancing blue hydrangea sepal coloration by applying aluminum sulfate through constant liquid fertilization}, volume={1305}, ISSN={["2406-6168"]}, DOI={10.17660/ActaHortic.2021.1305.60}, journal={III INTERNATIONAL SYMPOSIUM ON GROWING MEDIA, COMPOSTING AND SUBSTRATE ANALYSIS}, author={Landis, H. and Hicks, K. and McCall, I and Henry, J. B. and Whipker, B. E.}, year={2021}, pages={455–461} }
 @article{smith_jackson_whipker_fonteno_2021, title={Industrial hemp vegetative growth affected by substrate composition}, volume={1305}, ISSN={["2406-6168"]}, DOI={10.17660/ActaHortic.2021.1305.12}, journal={III INTERNATIONAL SYMPOSIUM ON GROWING MEDIA, COMPOSTING AND SUBSTRATE ANALYSIS}, author={Smith, J. T. and Jackson, B. E. and Whipker, B. E. and Fonteno, W. C.}, year={2021}, pages={83–89} }
 @article{cockson_whipker_2021, title={Refinement of conventional and OMRI fertilization of pot grown Solanum lycopersicum}, volume={1305}, ISSN={["2406-6168"]}, DOI={10.17660/ActaHortic.2021.1305.56}, journal={III INTERNATIONAL SYMPOSIUM ON GROWING MEDIA, COMPOSTING AND SUBSTRATE ANALYSIS}, author={Cockson, P. and Whipker, B. E.}, year={2021}, pages={431–436} }
 @article{cockson_veazie_davis_barajas_post_crozier_leon_patterson_whipker_2021, title={The Impacts of Micronutrient Fertility on the Mineral Uptake and Growth of Brassica carinata}, volume={11}, ISBN={2077-0472}, url={https://doi.org/10.3390/agriculture11030221}, DOI={10.3390/agriculture11030221}, abstractNote={Many abiotic factors impact the yield and growth of Brassica carinata (commonly referred to as carinata or Ethiopian mustard). Very little is known about carinata and how mineral nutrients impact its growth, and more specifically, the sufficiency values for fertility over the plant’s growth cycle and life stages. This study explored the impacts that plant nutrients, specifically micronutrients, can have on the growth and development of carinata over its distinct life stages (rosette, bolting, flowering, and pod set). Plants were grown under varying micronutrient concentrations (0, 25, 50, 75, 87.5, and 100%) of a modified Hoagland’s solution. Data were collected on plant height, canopy diameter, leaf tissue mineral nutrient concentrations, and biomass. The results demonstrated that micronutrient fertility has profound impacts on the production of Brassica carinata during different life stages. Boron (B) exclusion had the greatest impact on the growth and reproduction of Brassica carinata, with the death of the apical meristem that resulted in a lack of siliques or seeds at the lowest rate. Optimal relative elemental leaf tissue concentrations varied among micronutrient fertility concentrations and life stages. Certain elements exhibited linear increases in nutrient leaf tissue accumulation as solution concentration increased without reaching a maximum concentration during specific life stages. Other life stages and/or elements produced distinct plateau leaf tissue mineral concentrations despite increasing fertility treatment concentrations such as B in the rosette stage (47.2–50.0 mg·kg−1), copper (Cu) (bolting stage at 6.62–7.57 mg·kg−1), zinc (Zn) (bolting stage at 27.47–39.87 and flowering at 33.98–43.50 mg·kg−1), molybdenum (Mo) (flowering stage at 2.42–3.23 mg·kg−1), and manganese (Mn) (bolting stage at 117.03–161.63 mg·kg−1). This work demonstrates that Brassica carinata has different fertility demands and will accumulate differing leaf tissue concentrations during its life stages. This work serves as a baseline for further uptake and portioning work for Brassica carinata.}, number={3}, journal={AGRICULTURE-BASEL}, publisher={MDPI AG}, author={Cockson, Paul and Veazie, Patrick and Davis, Matthew and Barajas, Gabby and Post, Angela and Crozier, Carl R. and Leon, Ramon G. and Patterson, Robert and Whipker, Brian E.}, year={2021}, month={Mar}, pages={221} }
 @article{veazie_cockson_henry_perkins-veazie_whipker_2020, title={Characterization of Nutrient Disorders and Impacts on Chlorophyll and Anthocyanin Concentration of Brassica rapa var. Chinensis}, volume={10}, ISSN={["2077-0472"]}, DOI={10.3390/agriculture10100461}, abstractNote={Essential plant nutrients are needed at crop-specific concentrations to obtain optimal growth and yield. Foliar tissue analysis is the standard method for assessing nutrient levels in plants. Symptoms of nutrient deficiency or toxicity occur when the foliar tissue values become too low or high. Diagnostic nutrient deficiency criteria for Brassica rapa var. Chinensis (bok choy) is lacking in the current literature. In this study, green (‘Black Summer’) and purple (‘Red Pac’) bok choy plants were grown in silica sand culture, with control plants receiving a complete modified Hoagland’s all-nitrate solution, and nutrient-deficient plants induced by using a complete nutrient formula withholding a single nutrient. Tissue samples were collected at the first sign of visual disorder symptoms and analyzed for dry weight and nutrient concentrations of all plant essential elements. Six weeks into the experiment, the newest matured leaves were sampled for chlorophyll a, b, and total carotenoids concentrations for both cultivars, and total anthocyanin concentration in ‘Red Pac’. Compared to control plants, the dry weight of ‘Black Summer’ green bok choy was significantly lower for nitrogen (N), phosphorus (P), calcium (Ca), or boron (B) deficiency treatments, and nutrient concentrations were lower for all variables except iron (Fe) deficiency. Dry weight was less in ‘Red Pac’ plants grown without N, potassium (K), Ca, B, or molybdenum (Mo), and nutrient concentrations were lower for all except Mo-deficiency compared to controls. Total chlorophyll and total carotenoid concentrations were lower in leaves from N−, Fe-, and manganese- (Mn) deficient plants of both cultivars. Leaf anthocyanin concentration was lower only for K-, Ca-, and B-deficiencies in ‘Red Pac’. Our results indicate that visual symptoms of nutrient deficiency are well correlated with nutrient disorders. In contrast, changes in dry weight, chlorophyll, and anthocyanin did not show consistent changes across nutrient disorders.}, number={10}, journal={AGRICULTURE-BASEL}, author={Veazie, Patrick and Cockson, Paul and Henry, Josh and Perkins-Veazie, Penelope and Whipker, Brian}, year={2020}, month={Oct} }
 @article{cockson_schroeder-moreno_veazie_barajas_logan_davis_whipker_2020, title={Impact of Phosphorus on Cannabis sativa Reproduction, Cannabinoids, and Terpenes}, volume={10}, ISSN={["2076-3417"]}, DOI={10.3390/app10217875}, abstractNote={Many abiotic factors, such as mineral nutrients—including phosphorus (P)—fertility, can impact the yield and growth of Cannabis sativa. Given the economic portion of C. sativa is the inflorescence, the restriction of P fertility could impact floral development and quality could be detrimental. This study sought to track the impacts of varying P concentrations (3.75, 7.50, 11.25, 15.0, 22.50, and 30.0 mg·L−1) utilizing a modified Hoagland’s solution. This experiment examined plant height, diameter, leaf tissue mineral nutrient concentrations, and final fresh flower bud weight as well as floral quality metrics, such as cannabinoids and terpenes. The results demonstrated that during different life stages (vegetative, pre-flowering, flowering), P concentrations impact C. sativa growth and development and yield. Regarding the cannabinoid pools, results varied for the individual cannabinoid types. For the acid pools, increasing fertility concentrations above 11.25 mg·L−1 P did not result in any increase in cannabinoid concentrations. These results indicate that, if a crop is being produced under greenhouse conditions, specifically for cannabinoid production, an excessive P supply did not result in higher cannabinoid production. However, plants grown with a higher rate of P fertility (30.0 mg·L−1) had greater plant width and may result in more buds per plant.}, number={21}, journal={APPLIED SCIENCES-BASEL}, author={Cockson, Paul and Schroeder-Moreno, Michelle and Veazie, Patrick and Barajas, Gabby and Logan, David and Davis, Matthew and Whipker, Brian E.}, year={2020}, month={Nov} }
 @article{owen_jackson_fonteno_whipker_2020, title={Liming Requirements of Greenhouse Peat-based Substrates Amended with Pine Wood Chips as a Perlite Alternative}, volume={30}, ISSN={["1943-7714"]}, DOI={10.21273/HORTTECH04506-19}, abstractNote={Processed loblolly pine (Pinus taeda) wood has been investigated as a component in greenhouse and nursery substrates for many years. Specifically, pine wood chips (PWCs) have been uniquely engineered/processed into a nonfibrous blockular particle size suitable for use as a substrate aggregate. The objective of this research was to compare the dolomitic limestone requirements of plants grown in peat-based substrates amended with perlite or PWC. In a growth trial with ‘Mildred Yellow’ chrysanthemum (Chrysanthemum ×morifolium), peat-based substrates were amended to contain 0%, 10%, 20%, 30%, 40%, or 50% (by volume) perlite or PWC for a total of 11 substrates. Substrates were amended with dolomitic limestone at rates of 0, 3, 6, 9, or 12 lb/yard3, for a total of 55 substrate treatments. Results indicate that pH of substrates amended with ≥30% perlite or PWC need to be adjusted to similar rates of 9 to 12 lb/yard3 dolomitic limestone to produce similar-quality chrysanthemum plants. In a repeated study, ‘Moonsong Deep Orange’ african marigold (Tagetes erecta) plants were grown in the same substrates previously formulated (with the exclusion of the 50% ratio) and amended with dolomitic limestone at rates of 0, 3, 6, 9, 12, or 15 lb/yard3, for a total of 54 substrate treatments. Results indicate a similar dolomitic limestone rate of 15 lb/yard3 is required to adjust substrate pH of 100% peatmoss and peat-based substrates amended with 10% to 40% perlite or PWC aggregates to the recommended pH range for african marigold and to produce visually similar plants. The specific particle shape and surface characteristics of the engineered PWC may not be similar to other wood products (fiber) currently commercialized in the greenhouse industry, therefore the lime requirements and resulting substrate pH may not be similar for those materials.}, number={2}, journal={HORTTECHNOLOGY}, author={Owen, W. Garrett and Jackson, Brian E. and Fonteno, William C. and Whipker, Brian E.}, year={2020}, month={Apr}, pages={219–230} }
 @article{montgomery_henry_vann_whipker_huseth_mitasova_2020, title={Measures of Canopy Structure from Low-Cost UAS for Monitoring Crop Nutrient Status}, volume={4}, ISSN={2504-446X}, url={http://dx.doi.org/10.3390/drones4030036}, DOI={10.3390/drones4030036}, abstractNote={Deriving crop information from remotely sensed data is an important strategy for precision agriculture. Small unmanned aerial systems (UAS) have emerged in recent years as a versatile remote sensing tool that can provide precisely-timed, fine-grained data for informing management responses to intra-field crop variability (e.g., nutrient status and pest damage). UAS sensors with high spectral resolution used to compute informative vegetation indices, however, are practically limited by high cost and data dimensionality. This research extends spectral analysis for remote crop monitoring to investigate the relationship between crop health and 3D canopy structure using low-cost UAS equipped with consumer-grade RGB cameras. We used flue-cured tobacco as a case study due to its known sensitivity to fertility variation and nutrient-specific symptomology. Fertilizer treatments were applied to induce plant health variability in a 0.5 ha field of flue-cured tobacco. Multi-view stereo images from three UAS surveys collected during crop development were processed into orthoimages used to compute a visible band spectral index and photogrammetric point clouds using Structure from Motion (SfM). Plant structural metrics were then computed from detailed high resolution canopy surface models (0.05 m resolution) interpolated from the photogrammetric point clouds. The UAS surveys were complimented by nutrient status measurements obtained from plant tissues. The relationships between foliar nitrogen (N), phosphorus (P), potassium (K), and boron (B) concentrations and the UAS-derived metrics were assessed using multiple linear regression. Symptoms of N and K deficiencies were well captured and differentiated by the structural metrics. The strongest relationship observed was between canopy shape and N foliar concentration (adj. r2 = 0.59, increasing to adj. r2 = 0.81 when combined with the spectral index). B foliar concentration was consistently better predicted by canopy structure with a maximum adj. r2 = 0.41 observed at the latest growth stage surveyed. Overall, combining information about canopy structure and spectral reflectance increased model fit for all measured nutrients compared to spectral alone. These results suggest that an important relationship exists between relative canopy shape and crop health that can be leveraged to improve the usefulness of low cost UAS for precision agriculture.}, number={3}, journal={Drones}, publisher={MDPI AG}, author={Montgomery, Kellyn and Henry, Josh and Vann, Matthew and Whipker, Brian E. and Huseth, Anders and Mitasova, Helena}, year={2020}, month={Jul}, pages={36} }
 @article{whipker_cockson_smith_2020, title={Night interruption lighting equally effective as daylength extension in retaining the vegetative state of Cannabis mother plants}, volume={6}, ISBN={2374-3832}, DOI={10.1002/cft2.20001}, abstractNote={Crop, Forage & Turfgrass ManagementVolume 6, Issue 1 e20001 CROP MANAGEMENT—BRIEFS Night interruption lighting equally effective as daylength extension in retaining the vegetative state of Cannabis mother plants Brian E. Whipker, Corresponding Author Brian E. Whipker bwhipker@ncsu.edu orcid.org/0000-0003-0725-9712 Dep. of Horticultural Science, 2721 Founders Dr., North Carolina State University, Raleigh, NC, 27695 USA Correspondence Brian E. Whipker, Dep. of Horticultural Science, 2721 Founders Dr., North Carolina State University, Raleigh, NC 27695, USA Email: bwhipker@ncsu.eduSearch for more papers by this authorPaul Cockson, Paul Cockson orcid.org/0000-0001-6027-7990 Dep. of Horticultural Science, 2721 Founders Dr., North Carolina State University, Raleigh, NC, 27695 USASearch for more papers by this authorJames T. Smith, James T. Smith Dep. of Horticultural Science, 2721 Founders Dr., North Carolina State University, Raleigh, NC, 27695 USASearch for more papers by this author Brian E. Whipker, Corresponding Author Brian E. Whipker bwhipker@ncsu.edu orcid.org/0000-0003-0725-9712 Dep. of Horticultural Science, 2721 Founders Dr., North Carolina State University, Raleigh, NC, 27695 USA Correspondence Brian E. Whipker, Dep. of Horticultural Science, 2721 Founders Dr., North Carolina State University, Raleigh, NC 27695, USA Email: bwhipker@ncsu.eduSearch for more papers by this authorPaul Cockson, Paul Cockson orcid.org/0000-0001-6027-7990 Dep. of Horticultural Science, 2721 Founders Dr., North Carolina State University, Raleigh, NC, 27695 USASearch for more papers by this authorJames T. Smith, James T. Smith Dep. of Horticultural Science, 2721 Founders Dr., North Carolina State University, Raleigh, NC, 27695 USASearch for more papers by this author First published: 17 December 2019 https://doi.org/10.1002/cft2.20001Citations: 2Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume6, Issue12020e20001 RelatedInformation}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Whipker, Brian E. and Cockson, Paul and Smith, James T.}, year={2020} }
 @article{currey_metz_flax_litvin_whipker_2020, title={Restricting Phosphorous Can Manage Growth and Development of Containerized Sweet Basil, Dill, Parsley, and Sage}, volume={55}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI14882-20}, abstractNote={The objective of this research was to quantify the effects of phosphorous (P) concentrations on the growth, development, and tissue mineral nutrient concentrations of four popular culinary herbs commonly grown in containers. Seedlings of sweet basil (Ocimum basilicum ‘Italian Large Leaf’), dill (Anethum graveolens ‘Fernleaf’), parsley (Petroselinum crispum ‘Giant of Italy’), and sage (Salvia officinalis) were individually transplanted to 11.4-cm-diameter containers filled with soilless substrate comprising canadian sphagnum peatmoss and coarse perlite. Upon transplanting and throughout the experiment, seedlings were irrigated with solutions containing 0, 5, 10, 20, or 40 mg·L−1 P; all other macro- and micronutrient concentrations were the same across P concentrations. Plants were grown for 4 weeks in a greenhouse; after that time, data were collected. Relationships between height and width and P concentrations were nonlinear for all four species; height and width increased as P increased to more than 0 mg·L−1 until the species-specific maxima; after that time, no further increase occurred. The same trend was observed for the branch length of sweet basil and sage, and for internode length, leaf area, and shoot dry mass of all four species. Although visible P deficiency symptoms were observed for plants provided with 0 mg·L−1 P, there were no signs of P deficiency for plants provided with ≥5 mg·L−1 P, even though tissue P concentrations were below the recommended sufficiency ranges. As a result of this research, containerized sweet basil, dill, parsley, and sage can be provided with 5 to 10 mg·L−1 P during production to limit growth and produce plants without visible nutrient deficiency symptoms that are proportional to their containers.}, number={11}, journal={HORTSCIENCE}, author={Currey, Christopher J. and Metz, Vincent C. and Flax, Nicholas J. and Litvin, Alex G. and Whipker, Brian E.}, year={2020}, month={Nov}, pages={1722–1729} }
 @article{cockson_landis_smith_hicks_whipker_2019, title={Characterization of Nutrient Disorders of Cannabis sativa}, volume={9}, ISSN={["2076-3417"]}, DOI={10.3390/app9204432}, abstractNote={Essential plant nutrients are needed at crop-specific concentrations to obtain optimum growth or yield. Plant tissue (foliar) analysis is the standard method for measuring those levels in crops. Symptoms of nutrient deficiency occur when those tissue concentrations fall to a level where growth or yield is negatively impacted and can serve as a visual diagnostic tool for growers and researchers. Both nutrient deficiency symptoms and their corresponding plant tissue concentrations have not been established for cannabis. To establish nutrient concentrations when deficiency or toxicity symptoms are expressed, Cannabis sativa ‘T1’ plants were grown in silica sand culture, and control plants received a complete modified Hoagland’s all-nitrate solution, whereas nutrient-deficient treatments were induced with a complete nutrient formula withholding a single nutrient. Toxicity treatments were induced by increasing the element tenfold higher than the complete nutrient formula. Plants were monitored daily and, once symptoms manifested, plant tissue analysis of all essential elements was performed by most recent mature leaf (MRML) tissue analysis, and descriptions and photographs of nutrient disorder symptomology were taken. Symptoms and progressions were tracked through initial, intermediate, and advanced stages. Information in this study can be used to diagnose nutrient disorders in Cannabis sativa.}, number={20}, journal={APPLIED SCIENCES-BASEL}, author={Cockson, Paul and Landis, Hunter and Smith, Turner and Hicks, Kristin and Whipker, Brian E.}, year={2019}, month={Oct} }
 @article{landis_hicks_cockson_henry_smith_whipker_2019, title={Expanding Leaf Tissue Nutrient Survey Ranges for Greenhouse Cannabidiol-Hemp}, volume={5}, ISSN={["2374-3832"]}, DOI={10.2134/cftm2018.09.0081}, abstractNote={Core Ideas Leaf tissue nutrient concentration survey values do not exist for greenhouse CBD-hemp. Growers can use these ranges as a nutrient management tool for CBD-hemp stock plants. Different leaf tissue nutrient concentrations have been found in CBD-hemp cultivars. There are no researched nutrient recommendations specific to greenhouse CBD-hemp. CBD-hemp products have great market potential.}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Landis, Hunter and Hicks, Kristin and Cockson, Paul and Henry, Josh B. and Smith, James T. and Whipker, Brian E.}, year={2019}, month={Jan} }
 @article{henry_perkins-veazie_mccall_whipker_2019, title={Restricted Phosphorus Fertilization Increases the Betacyanin Concentration and Red Foliage Coloration of Alternanthera}, volume={144}, ISSN={["2327-9788"]}, DOI={10.21273/JASHS04702-19}, abstractNote={Phosphorus (P) deficiency commonly results in the development of red-to-purple coloration in plant foliage, typically attributed to anthocyanins. Betacyanins are a red pigment found in some plant species that do not produce anthocyanins, including Alternanthera sp. This study was conducted to investigate the effects of P nutrition on the betacyanin concentration and subsequent foliar coloration of ‘Purple Prince’, ‘Brazilian Red Hots’, and ‘Little Ruby’ alternanthera (Alternanthera brasiliana). The purpose of this study was to determine whether P fertilization management could enhance the coloration and aesthetic appeal of alternanthera. Custom fertilizers provided P concentrations of 0, 2.5, 5, 10, and 20 mg·L−1 P. One-half of the plants from each P concentration were restricted to 0 mg·L−1 P 1 month after transplant to determine whether adequate size could be attained before withholding P. Differences in P response were observed among cultivars for hue, betacyanin content, and plant size. Concentrations ≤5 mg·L−1 P resulted in plants that were more compact in terms of plant height and diameter, had deeper red foliage coloration, and greater foliar betacyanins compared with plants grown with greater P concentrations. Plants initially grown with 5 or 10 mg·L−1 P attained marketable size before P restriction and developed more red pigmentation compared with plants grown with P for the remaining duration of the study. Regression analysis demonstrated height was maximized with 3 to 8 mg·L−1 P, diameter with 4.1 to 8.4 mg·L−1 P, and branching with 10.0 mg·L−1 P. Foliar betacyanin concentrations were greatest in plants grown without P, reaching 269 mg/100 g fresh weight, whereas plants grown with 10 or 20 mg·L−1 P were 95% less (averaged ≈13 mg/100 g fresh weight). This study demonstrates that P restriction can benefit the aesthetic appeal of alternanthera and provides the first confirmation that P nutrition is associated with betacyanin accumulation.}, number={4}, journal={JOURNAL OF THE AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE}, author={Henry, Josh B. and Perkins-Veazie, Penelope and McCall, Ingram and Whipker, Brian E.}, year={2019}, month={Jul}, pages={264–273} }
 @article{henry_vann_mccall_cockson_whipker_2018, title={Nutrient Disorders o Burley and Flue-Cured Tobacco: Part 1-Macronutrient Deficiencies}, volume={4}, ISSN={["2374-3832"]}, DOI={10.2134/cftm2017.11.0076}, abstractNote={Core Ideas
Recognizing macronutrient disorders is important for commercial production.
Foliar nutrient concentrations were identified for burley and flue‐cured tobacco.
Symptoms and critical values were compared with published results.
}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, publisher={American Society of Agronomy}, author={Henry, Josh B. and Vann, Matthew and McCall, Ingram and Cockson, Paul and Whipker, Brian E.}, year={2018}, month={Mar} }
 @article{henry_vann_mccall_cockson_whipker_2018, title={Nutrient Disorders of Burley and Flue-Cured Tobacco: Part 2-Micronutrient Disorders}, volume={4}, ISSN={["2374-3832"]}, DOI={10.2134/cftm2017.11.0077}, abstractNote={Core Ideas
Recognizing micronutrient disorders is important for commercial production.
Unique, previously unobserved nutrient disorder symptoms were observed.
Foliar nutrient concentrations were identified for burley and flue‐cured tobacco.
Symptoms and critical values were compared with published results.
}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, publisher={American Society of Agronomy}, author={Henry, Josh B. and Vann, Matthew and McCall, Ingram and Cockson, Paul and Whipker, Brian E.}, year={2018}, month={Mar} }
 @article{henry_mccall_whipker_2018, title={Phosphorus Restriction as an Alternative to Chemical Plant Growth Retardants in Angelonia and New Guinea Impatiens}, volume={28}, ISSN={["1943-7714"]}, DOI={10.21273/horttech03939-17}, abstractNote={Chemical plant growth retardants (PGRs) are commonly used to produce compact bedding plants. Few PGRs are labeled for sensitive species because of the concern of excessive restriction of stem elongation or phytotoxicity. Growers are therefore presented with a dilemma: produce untreated plants that may be too tall or risk applying a PGR that can potentially lead to irreversible aesthetic damage to the plant. Nutrient restriction, specifically of phosphorus (P), may be used to control plant height. This study was conducted to determine if restricting P fertilization yielded comparable growth control to plants produced with PGRs. Two cultivars each of new guinea impatiens (Impatiens hawkeri) and angelonia (Angelonia angustifolia) were grown using five fertilizers that varied by P concentration (0, 2.5, 5, 10, and 20 ppm). Half of the plants from each P fertilizer concentration were treated with paclobutrazol at 4 and 5 weeks after transplant for angelonia and new guinea impatiens, respectively. On termination of the experiment, data were collected for height, diameter, and dry weight, which were used to determine a growth index (GI). Angelonia GI values were maximized with 7–9 ppm P, whereas new guinea impatiens GI was maximized with 8–11 ppm P. Concentrations of 3–5 ppm P provided similar height control to plants grown with nonlimiting P and a paclobutrazol application. Concentrations of ≤2.5 ppm P resulted in low-quality plants with visual symptoms of P deficiency. These results indicate that a narrow range of P concentrations may be used to control stem elongation and keep plants compact.}, number={2}, journal={HORTTECHNOLOGY}, author={Henry, Josh B. and McCall, Ingram and Whipker, Brian E.}, year={2018}, month={Apr}, pages={136–142} }
 @article{henry_mccall_nelson_whipker_2018, title={Source-sink interactions lead to atypical reproductive stage phosphorus deficiency symptoms on the upper foliage of Capsicum annuum and Chrysanthemum x morifolium}, volume={238}, ISSN={["1879-1018"]}, DOI={10.1016/j.scienta.2018.04.069}, abstractNote={Phosphorus (P) restriction has become more prevalent in floriculture production to control growth and reduce fertilizer waste. With low P fertilization practices, growers are more likely to develop P deficiency in their crops. Symptoms of a reproductive stage P deficiency were reported in which symptomology occurs on the foliage directly below the flowers or fruit. To induce and describe these symptoms, ornamental peppers (Capsicum annuum L.) and chrysanthemums (Chrysanthemum ×morifolium Ramat.) were grown initially with P fertilization, but half the plants were later restricted to 0 mg L−1 P upon floral initiation. Plants that were P restricted developed symptoms of chlorosis, olive green spotting, and necrosis on the upper foliage below the reproductive structures, while central foliage remained asymptomatic. ‘Crystal Misty Purple’ chrysanthemums developed unique symptoms of upper leaf purpling. Phosphorus movement within the plant was quantified via tissue division and analysis. The highest tissue P concentrations were in the flowers or fruit for both species, regardless of symptoms. Up to 80% of the total P in aboveground tissues was in the flowers and fruit of symptomatic plants. Vegetative tissue P concentrations were significantly lower in symptomatic plants compared to the asymptomatic controls, indicating that large quantities of P were translocated from vegetative tissues to the developing reproductive tissues. Remobilized P from the lower tissues appeared to bypass the upper foliage in favor of the flowers and fruit. Thus, the developing upper foliage was deprived of P, leading to P deficiency symptoms due to competition with the maturing flowers and fruit.}, journal={SCIENTIA HORTICULTURAE}, author={Henry, Josh B. and McCall, Ingram and Nelson, Paul V. and Whipker, Brian E.}, year={2018}, month={Aug}, pages={288–294} }
 @article{henry_mccall_jackson_whipker_2017, title={Growth Response of Herbaceous Ornamentals to Phosphorus Fertilization}, volume={52}, ISSN={["2327-9834"]}, DOI={10.21273/hortsci12256-17}, abstractNote={A series of experiments investigated the effects of increasing phosphate–phosphorus (P) concentrations on the growth and development of four horticultural species. In experiment 1, petunia [Petunia atkinsiana (Sweet) D. Don ex W.H. Baxter] plants were grown using eight P concentrations, and we found that the upper bound for plant growth was at 8.72–9.08 mg·L−1 P, whereas concentrations ≤2.5 mg·L−1 P caused P deficiency symptoms. Experiment 2 investigated P growth response in two cultivars each of New Guinea impatiens (Impatiens hawkeri W. Bull) and vinca [Catharanthus roseus (L.) G. Don]. Growth for these plants was maximized with 6.43–12.42 mg·L−1 P. In experiment 3, ornamental peppers (Capsicum annuum L. ‘Tango Red’) were given an initial concentration of P for 6 weeks and then switched to 0 mg·L−1 P to observe whether plants could be supplied with sufficient levels of P, and finished without P to keep them compact. Plants switched to restricted P began developing P deficiency symptoms within 3 weeks; however, restricting P successfully limited plant growth. These experiments indicated that current P fertilization regimens exceed the P requirements of these bedding plants, and depending on species, concentrations of 5–15 mg·L−1 P maximize growth.}, number={10}, journal={HORTSCIENCE}, author={Henry, Josh B. and McCall, Ingram and Jackson, Brian and Whipker, Brian E.}, year={2017}, month={Oct}, pages={1362–1367} }
 @article{barnes_nelson_hesterberg_shi_whipker_2017, title={Modeling impact of nitrogen carrier and concentration on root substrate pH}, volume={40}, ISSN={["1532-4087"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85029409669&partnerID=MN8TOARS}, DOI={10.1080/01904167.2016.1143502}, abstractNote={ABSTRACT We conducted an experiment to quantify the effects on substrate pH from nitrogen (N) carrier and concentration. We used four concentrations of N (3.5–14 mM) and five fractions of ammonium (NH4+) (0–80% NH4+ of total N) that are found in commercially available fertilizers. Fertilizers were applied to fallow 14-cm-diameter pots (1.29 L) filled with a 3 peat:1 perlite (v/v) substrate amended with non-residual powdered calcium carbonate to raise the substrate pH to approximately 6.0. Harvests occurred at 20 and 42 days. Significant effects in the model included main effects of N carrier and N concentration, their squared terms, an interaction effect, and a time × N carrier. The fraction of NH4+ accounted for 45.0% of variation in substrate pH, and N concentration accounted for 1.5% of the total R2 of 76.7%. Substrate acidification was likely due to the physiological fertilizer effect and nitrification.}, number={15}, journal={JOURNAL OF PLANT NUTRITION}, author={Barnes, Jared and Nelson, Paul V. and Hesterberg, Dean and Shi, Wei and Whipker, Brian E.}, year={2017}, pages={2101–2108} }
 @article{barker_mccall_whipker_2016, title={Growth control of 'Imperial Dark Blue' Plumbago with ethephon, flurprimidol, and paclobutrazol substrate drenches}, volume={26}, number={4}, journal={HortTechnology}, author={Barker, A. and McCall, I. and Whipker, B. E.}, year={2016}, pages={493–496} }
 @article{barnes_whipker_mccall_frantz_2016, title={Nutrient disorders of Dianthus 'Bouquet Purple'}, volume={39}, ISSN={["1532-4087"]}, DOI={10.1080/01904167.2016.1143504}, abstractNote={ABSTRACT ‘Bouquet Purple’ pinks (Dianthus sp.) were grown in silica-sand culture to induce and photograph symptoms of nutritional disorders. Plants received a complete modified Hoagland's all-nitrate (NO3) solution. Nutrient-deficient treatments were induced with a complete nutrient formula minus one of the nutrients, and a boron (B)-toxicity treatment was induced by increasing B 10-fold in the complete nutrient formula. Plants were monitored daily to document sequential series of symptoms as they developed. Typical symptomology of nutrient disorders and corresponding tissue concentrations were determined. All treatments exhibited deficiency symptomology. Disorders for nitrogen (N), iron (Fe), calcium (Ca), and sulfur (S) were the first to manifest in pinks. Unique symptomology was observed for plants grown under potassium- (K), B-, copper- (Cu), and molybdenum- (Mo) deficient conditions, which supported the need for a species-specific approach when characterizing nutrient disorders of floriculture crops.}, number={13}, journal={JOURNAL OF PLANT NUTRITION}, author={Barnes, Jared and Whipker, Brian and McCall, Ingram and Frantz, Jonathan}, year={2016}, pages={1950–1957} }
 @article{owen_jackson_whipker_fonteno_2016, title={Paclobutrazol drench activity not affected in sphagnum peat-based substrates amended with pine wood chip aggregates}, volume={26}, number={2}, journal={HortTechnology}, author={Owen, W. G. and Jackson, B. E. and Whipker, B. E. and Fonteno, W. C.}, year={2016}, pages={156–163} }
 @article{owen_jackson_whipker_fonteno_2016, title={Pine wood chips as an alternative to perlite in greenhouse substrates: Nitrogen requirements}, volume={26}, number={2}, journal={HortTechnology}, author={Owen, W. G. and Jackson, B. E. and Whipker, B. E. and Fonteno, W. C.}, year={2016}, pages={199–205} }
 @inproceedings{barnes_whipker_mccall_frantz_2015, title={Characterization of nutrient disorders of Abutilon x hybridum 'Bella Yellow'}, volume={1062}, DOI={10.17660/actahortic.2015.1062.3}, booktitle={International conference and exhibition on soilless culture}, author={Barnes, J. and Whipker, B. and McCall, I. and Frantz, J.}, year={2015}, pages={29–37} }
 @inproceedings{barnes_whipker_mccall_frantz_2015, title={Characterization of nutrient disorders of Dahlia x hybrida 'Maxi Morelia'}, volume={1062}, DOI={10.17660/actahortic.2015.1062.4}, abstractNote={Dahlia A— hybrida ‘Maxi Morelia’ plants were grown in silica sand culture to induce and photograph symptoms of nutritional disorders. Plants were grown with a complete modified Hoagland’s all nitrate solution: (macronutrients in mM) 15 NO3-N, 1.0 PO4-P, 6.0 K, 5.0 Ca, 2.0 Mg, and 2.0 SO4-S, plus µM concentrations of micronutrients, 72 Fe, 18 Mn, 3 Cu, 3 Zn, 45 B, and 0.1 Mo. The nutrient deficiency treatments were induced with a complete nutrient formula minus one of the nutrients. Reagent grade chemicals and deionized water of 18-mega ohms purity were used to formulate treatment solutions. Boron toxicity was also induced by increasing the element 10A— higher than the complete nutrient formula. The plants were automatically irrigated. The solution drained from the bottom of the pot and was captured for reuse. A complete replacement of nutrient solutions was done weekly. Plants were monitored daily to document and photograph sequential series of symptoms as they developed. Typical symptomology of nutrient disorders and critical tissue concentrations are presented.}, booktitle={International conference and exhibition on soilless culture}, author={Barnes, J. and Whipker, B. and McCall, I. and Frantz, J.}, year={2015}, pages={39–47} }
 @inproceedings{barnes_whipker_mccall_frantz_2015, title={Characterization of nutrient disorders of Fuchsia x hybrida 'Gartenmeister Bonstedt'}, volume={1062}, DOI={10.17660/actahortic.2015.1062.5}, abstractNote={Fuchsia A— hybrida ‘Gartenmeister Bonstedt’ plants were grown in silica sand culture to induce and photograph nutritional disorder symptoms. Plants were grown with a complete modified Hoagland's all nitrate solution: (macronutrients in mM) 15 NO3-N, 1.0 PO4-P, 6.0 K, 5.0 Ca, 2.0 Mg, and 2.0 SO4-S, plus µM concentrations of micronutrients, 72 Fe, 18 Mn, 3 Cu, 3 Zn, 45 B, and 0.1 Mo. The nutrient deficiency treatments were induced with a complete nutrient formula minus one of the nutrients. Reagent grade chemicals and deionized water of 18-mega ohms purity were used to formulate treatment solutions. Boron toxicity was also induced by increasing the element 10A— higher than the complete nutrient formula. The plants were automatically irrigated. The solution drained from the bottom of the pot and was captured for reuse. A complete replacement of nutrient solutions was done weekly. Plants were monitored daily to document and photograph sequential series of symptoms as they developed. Typical symptomology of nutrient disorders is presented.}, booktitle={International conference and exhibition on soilless culture}, author={Barnes, J. and Whipker, B. and McCall, I. and Frantz, J.}, year={2015}, pages={49–57} }
 @inproceedings{barnes_whipker_mccall_frantz_2015, title={Characterization of nutrient disorders of Senecio cineraria 'Silver Mist'}, volume={1062}, DOI={10.17660/actahortic.2015.1062.6}, abstractNote={Senecio cineraria ‘Silver Mist’ plants were grown in silica sand culture to induce and photograph nutritional disorder symptoms. Plants were grown with a complete modified Hoagland’s all nitrate solution: (macronutrients in mM) 15 NO3-N, 1.0 PO4-P, 6.0 K, 5.0 Ca, 2.0 Mg, and 2.0 SO4-S, plus µM concentrations of micronutrients, 72 Fe, 18 Mn, 3 Cu, 3 Zn, 45 B, and 0.1 Mo. The nutrient deficiency treatments were induced with a complete nutrient formula minus one of the nutrients. Reagent grade chemicals and deionized water of 18-mega ohms purity were used to formulate treatment solutions. Boron toxicity was also induced by increasing the element 10A— higher than the complete nutrient formula. The plants were automatically irrigated. The solution drained from the bottom of the pot and was captured for reuse. A complete replacement of nutrient solutions was done weekly. Plants were monitored daily to document and photograph sequential series of symptoms as they developed. Typical symptomology of nutrient disorders and critical tissue concentrations are presented.}, booktitle={International conference and exhibition on soilless culture}, author={Barnes, J. and Whipker, B. and McCall, I. and Frantz, J.}, year={2015}, pages={59–66} }
 @article{ahmad_whipker_dole_2015, title={Flurprimidol preplant corm soaks or drenches affect potted gladiolus production}, volume={1104}, ISSN={["2406-6168"]}, DOI={10.17660/actahortic.2015.1104.16}, journal={XXIX INTERNATIONAL HORTICULTURAL CONGRESS ON HORTICULTURE: SUSTAINING LIVES, LIVELIHOODS AND LANDSCAPES (IHC2014): INTERNATIONAL SYMPOSIUM ON ORNAMENTAL HORTICULTURE IN THE GLOBAL GREENHOUSE}, author={Ahmad, I. and Whipker, B. E. and Dole, J. M.}, year={2015}, pages={103–108} }
 @article{ahmad_whipker_dole_2015, title={Paclobutrazol or Ancymidol Effects on Postharvest Performance of Potted Ornamental Plants and Plugs}, volume={50}, ISSN={["2327-9834"]}, DOI={10.21273/hortsci.50.9.1370}, abstractNote={Effects of paclobutrazol and ancymidol on postharvest performance and growth control of potted sunflower (Helianthus annuus L.), zinnia (Zinnia elegans Jacq.) and marigold (Tagetes erecta L.), petunia (Petunia ×hybrida Vilm.) plugs, respectively, were studied. Paclobutrazol was applied as a drench at 0, 1.0, 2.0, or 4.0 mg of a.i. per 15.2-cm pot for sunflower and 0, 0.5, 1.0, or 2.0 mg per 12.5-cm pot for zinnia, while ancymidol was applied at 0, 40, 80, and 160 mg·L−1 with a volume of 0.21 L·m−2 as a foliar spray for marigolds or petunia plug crops. With an increase in paclobutrazol dose or ancymidol concentration, plant growth (plant height and diameter, shoot fresh or dry weight) was controlled for all species tested. Use of 1.0–2.0 mg paclobutrazol per pot produced 21% to 28% shorter plants with 12% to 15% smaller plant diameter, 13% to 19% less shoot fresh weight, 15% to 21% less dry weight, and darker green foliage color for potted sunflower than nontreated plants. Treatment with 1.0–4.0 mg paclobutrazol per pot delayed first wilting by 0.7–1.4 days compared with nontreated plants. For zinnia, 0.5–1.0 mg paclobutrazol controlled plant growth, produced dark green foliage, and extended shelf life by delaying first wilting by 2.6–3.9 days and second wilting by 1.4–2.0 days than nontreated plants. For marigold and petunia plugs, 40–80 mg·L−1 ancymidol provided ample growth control with darker green foliage; however, postharvest longevity was extended only when plugs were sprayed with 160 mg·L−1 ancymidol. During simulated storage and shipping, plant growth retardants maintained darker green foliage for potted sunflower, zinnia, and marigold plugs and prevented postharvest stem elongation of petunia plugs. In summary, use of plant growth retardants effectively controlled excessive plant growth and extended shelf life of potted plants and plugs.}, number={9}, journal={HORTSCIENCE}, author={Ahmad, Iftikhar and Whipker, Brian E. and Dole, John M.}, year={2015}, month={Sep}, pages={1370–1374} }
 @article{ahmad_dole_whipker_2015, title={Paclobutrazol or uniconazole effects on ethylene sensitivity of potted ornamental plants and plugs}, volume={192}, ISSN={["1879-1018"]}, DOI={10.1016/j.scienta.2015.04.032}, abstractNote={Effects of paclobutrazol on postharvest ethylene sensitivity of potted cuphea (Cuphea hyssopifolia Kunth) and petunia (Petunia × hybrida Vilm.) plants, and uniconazole on portulaca (Portulaca oleracea L.) plugs were evaluated. Paclobutrazol was applied as a drench at 0, 1, 2, or 4 mg L−1 per 12.5 cm pot for cuphea, or 0, 2, 4, or 8 mg L−1 per 15.2 cm pot for petunia, while uniconazole was applied at 0, 2.0, 4.0, or 8.0 mg L−1 with a volume of 0.21 L m−2 as a foliar spray for portulaca plugs. With an increase in paclobutrazol dose or uniconazole concentration, plant growth [plant height and diameter (potted plants only), shoot fresh weight, or dry weight] was controlled for all species tested. While use of paclobutrazol or uniconazole controlled excessive plant growth of all three species, the plant growth retardants had no effect on postharvest ethylene sensitivity as most flowers abscised from all plants exposed to exogenous ethylene. However, both paclobutrazol and uniconazole reduced postharvest flower abscission of plants not treated with exogenous ethylene. During simulated shipping and marketing, paclobutrazol and uniconazole maintained darker foliage and controlled height. Drench applications of 2–4 mg L−1 paclobutrazol for cuphea and 4–8 mg L−1 for petunia potted plants and spray applications of 4–8 mg L−1 uniconazole for portulaca plugs produced compact, high quality plants while also extending postharvest longevity and quality.}, journal={SCIENTIA HORTICULTURAE}, author={Ahmad, Iftikhar and Dole, John M. and Whipker, Brian E.}, year={2015}, month={Aug}, pages={350–356} }
 @article{carlson_dole_whipker_2015, title={Plant Growth Regulator Drenches Suppress Foliage and Inflorescence Height of 'Leia' Pineapple Lily}, volume={25}, ISSN={["1943-7714"]}, DOI={10.21273/horttech.25.1.105}, abstractNote={Plant growth regulators (PGRs) are used to control excessive plant growth in potted crops to improve quality and compactness for shipping and display. Pineapple lily (Eucomis sp.), a recent introduction to the potted crop market, can have excessive foliage growth and inflorescence height making the use of PGRs desirable. Bulbs of ‘Leia’ pineapple lily were forced in the greenhouse and drenched at leaf whorl emergence with three PGRs at five different concentrations: 1) flurprimidol (0.25, 0.5, 1.0, 2.0, and 4.0 mg per 6.5-inch pot), 2) uniconazole (0.25, 0.5, 1.0, 2.0, and 4.0 mg/pot), or 3) paclobutrazol (0.5, 1.0, 2.0, 4.0 and 8.0 mg/pot) and an untreated control. As concentration increased, days to anthesis increased and foliage height decreased for each PGR. Paclobutrazol (4.0 and 8.0 mg/pot), uniconazole (4.0 mg/pot), and flurprimidol (2.0 and 4.0 mg/pot) treatments resulted in excessive stunting with none of the plants being marketable. Flurprimidol had the greatest influence on plant growth among all the PGRs. Acceptable concentrations for each PGR are paclobutrazol at 0.5 to 2.0 mg/pot, uniconazole at 0.25 to 2.0 mg/pot, and flurprimidol at 0.5 to 1.0 mg/pot based on percentage of marketable plants and foliage and inflorescence height suppression without excessively increasing the number of days to anthesis.}, number={1}, journal={HORTTECHNOLOGY}, author={Carlson, Alicain S. and Dole, John M. and Whipker, Brian E.}, year={2015}, month={Feb}, pages={105–109} }
 @inproceedings{whipker_mccall_barnes_frantz_2014, title={Automated system for inducing nutrient disorders utilized in grower-based guides: Exacum affine 'Royal Dane Blue'}, volume={1034}, DOI={10.17660/actahortic.2014.1034.76}, booktitle={International symposium on growing media and soilless cultivation}, author={Whipker, B. E. and McCall, I. and Barnes, J. and Frantz, J.}, year={2014}, pages={599–605} }
 @inproceedings{barnes_whipker_mccall_frantz_2014, title={Characterization of nutrient disorders of Gazania rigens 'Daybreak White'}, volume={1034}, DOI={10.17660/actahortic.2014.1034.56}, abstractNote={Gazania rigens ‘Daybreak White’ plants were grown in silica sand culture to induce and photograph symptoms of nutritional disorders. Plants were grown with a complete modified Hoagland’s all nitrate solution: (macronutrients in mM) 15 NO3-N, 1.0 PO4-P, 6.0 K, 5.0 Ca, 2.0 Mg, and 2.0 SO4-S, plus µM concentrations of micronutrients, 72 Fe, 18 Mn, 3 Cu, 3 Zn, 45 B, and 0.1 Mo. The treatments causing nutrient deficient symptoms were induced with a complete nutrient formula minus one of the nutrients. Boron toxicity was also induced by increasing the element 10× higher than the complete nutrient formula. Reagent grade chemicals and deionized water of 18-mega ohms purity were used to formulate treatment solutions. The plants were automatically irrigated. The solution drained from the bottom of the pot and was captured for reuse. A complete replacement of nutrient solutions was done weekly. Plants were monitored daily to document and photograph sequential series of symptoms as they developed. Typical symptomology of nutrient disorders and critical tissue concentrations are presented. Out of the thirteen treatments, eleven exhibited symptoms. Deficiency symptoms of N, S, and Ca were first to manifest. Should nutritional disorders arise growers should first consider these three problems when trying to determine the possible cause.}, booktitle={International symposium on growing media and soilless cultivation}, author={Barnes, J. and Whipker, B. E. and McCall, I. and Frantz, J.}, year={2014}, pages={459–464} }
 @inproceedings{jin_fair_whipker_mccall_frantz_2014, title={Characterization of nutrient disorders of Solenostemon scutellarioides 'Lime Light' in silica-sand culture}, volume={1034}, DOI={10.17660/actahortic.2014.1034.77}, abstractNote={Solenostemon scutellarioides ‘Lime Light’ were grown in silica-sand culture to induce and catalog nutritional disorder symptoms. Plants were grown with a complete, modified Hoagland’s solution (macronutrients in mM, micronutrients in µM): 15.0 NO3-N, 1.0 PO4-P, 6.0 K, 5.0 Ca, 2.0 Mg, 2.0 SO4-S, 72.0 Fe, 18.0 Mn, 3.0 Cu, 3.0 Zn, 45.0 B, and 0.1 Mo. The control plants were grown using a nutrient formula containing all essential nutrients. Each nutrient deficiency treatment was induced by using the complete formula minus only one essential nutrient. Reagent grade chemicals and deionized water of 18-mega ohms purity were used to formulate treatment solutions. Toxicity of boron was also induced by increasing the element 10X higher than the complete formula. Plants were automatically irrigated every 2 hours, drained from the pot bottom and solution captured for reuse. The nutrient solutions were replaced weekly. Researchers monitored plants daily to document and catalog sequential onset of symptoms. Symptoms of N, P, Ca, Fe deficiency and B toxicity were the first disorders to exhibit in Solenostemon scutellarioides ‘Limelight’. The chartreuse coloration of this cultivar compounded difficulties in assessing symptomology of some nutrient disorders, particularly those that manifested with yellowing discoloration or chlorosis.}, booktitle={International symposium on growing media and soilless cultivation}, author={Jin, Y. and Fair, B. A. and Whipker, B. E. and McCall, I. and Frantz, J.}, year={2014}, pages={607–613} }
 @article{barnes_nelson_whipker_hesterberg_shi_2014, title={Fertilizer Formulation Effect on pH of Fallow Versus Planted Container Substrate}, volume={1034}, ISSN={["0567-7572"]}, DOI={10.17660/actahortic.2014.1034.57}, abstractNote={From previous work testing the impact of 30 fertilizers on substrate pH, five fertilizer formulations that elicited the widest range of substrate pH biotic impacts during Salvia farinacea ‘Evolution White’ cultivation were chosen for a follow up study to determine the abiotic impact of these fertilizers on fallow substrate. A 3 sphagnum peat moss : 1 perlite substrate was formulated and adjusted to pH 5.6. Three sets of pots (14 cm diameter) were filled with substrate. Salvia plugs were installed in the first set for cultivation while the second set was left fallow followed by fertilization of both sets with 400 mL of fertilizer solution with each irrigation (each at 7 mmol nitrogen concentration and pH 4.2 ± 0.1) to bring them to approximately container capacity. The third set of pots (control) was left fallow and irrigated with 400 mL deionized water instead of fertilizer solution. When cultivated substrates dried to approximately 50% of container capacity, 200 mL of fertilizer solution was applied to sets one and two and 200 mL deionized water to set three for a total of 11 applications. Substrates were harvested after 3 and 6 weeks. The pH of control substrate was 5.69 for both harvests. For the first and second harvest, cultivated substrate pH ranged from 6.08 to 5.03 and 6.22 to 4.85, respectively, while pH values of fallow substrate that received fertilizer solutions ranged from 5.66 to 5.19 and 5.44 to 4.97, respectively. Contrary to the expected abiotic effect of these acidic fertilizer solutions, pH in the fertilized fallow pots increased or decreased in a similar but diminished fashion to the changes that occurred to the pH in the cultivated pots. These results suggested a biotic effect in the fallow substrates due possibly to microflora and nitrification and indicate the need to take into account a biotic effect of microbes when assessing the abiotic effect of fertilizer solutions on substrate pH.}, journal={INTERNATIONAL SYMPOSIUM ON GROWING MEDIA AND SOILLESS CULTIVATION}, author={Barnes, J. and Nelson, P. and Whipker, B. E. and Hesterberg, D. and Shi, W.}, year={2014}, pages={465–469} }
 @article{barnes_whipker_mccall_2014, title={Optimizing Fertilizer Rates for Two Cultivars of Graziosa Geraniums}, volume={1034}, ISSN={["0567-7572"]}, DOI={10.17660/actahortic.2014.1034.58}, journal={INTERNATIONAL SYMPOSIUM ON GROWING MEDIA AND SOILLESS CULTIVATION}, author={Barnes, J. and Whipker, B. E. and McCall, I.}, year={2014}, pages={471–476} }
 @article{ahmad_whipker_dole_mccall_2014, title={Paclobutrazol and ancymidol lower water use of potted ornamental plants and plugs}, volume={79}, number={6}, journal={European Journal of Horticultural Science}, author={Ahmad, I. and Whipker, B. E. and Dole, J. M. and McCall, I.}, year={2014}, pages={318–326} }
 @article{barnes_nelson_whipker_dickey_hesterberg_shi_2014, title={Statistical model for describing macronutrient impacts on container substrate pH over time}, volume={49}, number={2}, journal={HortScience}, author={Barnes, J. and Nelson, P. and Whipker, B. E. and Dickey, D. A. and Hesterberg, D. and Shi, W.}, year={2014}, pages={207–214} }
 @inproceedings{barnes_whipker_mccall_frantz_2013, title={Characterization of nutrient disorders of Gomphrena globosa 'Las Vegas purple'}, volume={982}, DOI={10.17660/actahortic.2013.982.6}, booktitle={International symposium on responsible peatland management and growing media production}, author={Barnes, J. and Whipker, B. and McCall, I. and Frantz, J.}, year={2013}, pages={69–74} }
 @article{krug_whipker_mccall_frantz_2013, title={Elevated relative humidity increases the incidence of distorted growth and boron deficiency in bedding plant plugs}, volume={48}, number={3}, journal={HortScience}, author={Krug, B. A. and Whipker, B. E. and McCall, I. and Frantz, J.}, year={2013}, pages={311–313} }
 @article{barnes_whipker_buhler_mccall_2013, title={Greenhouse and landscape growth of tiger lily cultivars following flurprimidol preplant bulb soaks}, volume={23}, number={6}, journal={HortTechnology}, author={Barnes, J. and Whipker, B. and Buhler, W. and McCall, I.}, year={2013}, pages={820–822} }
 @article{barnes_nelson_fonteno_whipker_jeong_2013, title={Impact of Mature Dairy Manure Compost and Water Content on Wettability and Bulk Density in Peat Moss-Perlite Root Substrate}, volume={982}, ISSN={["2406-6168"]}, DOI={10.17660/actahortic.2013.982.7}, abstractNote={ISHS International Symposium on Responsible Peatland Management and Growing Media Production IMPACT OF MATURE DAIRY MANURE COMPOST AND WATER CONTENT ON WETTABILITY AND BULK DENSITY IN PEAT MOSS-PERLITE ROOT SUBSTRATE}, journal={INTERNATIONAL SYMPOSIUM ON RESPONSIBLE PEATLAND MANAGEMENT AND GROWING MEDIA PRODUCTION}, author={Barnes, J. and Nelson, P. and Fonteno, W. C. and Whipker, B. and Jeong, Ka-Yeon}, year={2013}, pages={75–80} }
 @inproceedings{owen_jackson_fonteno_whipker_2013, title={Pine wood chips as an alternative to perlite: Cultural parameters to consider (c)}, volume={1014}, DOI={10.17660/actahortic.2013.1014.77}, booktitle={Proceedings of the international plant propagators' society}, author={Owen, W. G. and Jackson, B. E. and Fonteno, W. C. and Whipker, B. E.}, year={2013}, pages={345–349} }
 @article{fair_whipker_mccall_buhler_2012, title={Height control of 'Hot Lips' Hybrid sage to flurprimidol substrate drench}, volume={22}, number={4}, journal={HortTechnology}, author={Fair, B. A. and Whipker, B. and McCall, I. and Buhler, W.}, year={2012}, pages={539–541} }
 @article{barnes_whipker_mccall_frantz_2012, title={Nutrient disorders of 'Evolution' Mealy-cup Sage}, volume={22}, number={4}, journal={HortTechnology}, author={Barnes, J. and Whipker, B. and McCall, I. and Frantz, J.}, year={2012}, pages={502–508} }
 @article{currey_lopez_krug_mccall_whipker_2012, title={Substrate drenches containing flurprimidol suppress height of 'Nellie White' Easter lilies}, volume={22}, number={2}, journal={HortTechnology}, author={Currey, C. J. and Lopez, R. G. and Krug, B. A. and McCall, I. and Whipker, B. E.}, year={2012}, pages={164–168} }
 @article{davis_niedziela_reddy_whipker_frantz_2011, title={NUTRIENT DISORDER SYMPTOMOLOGY AND FOLIAR CONCENTRATIONS OF CLERODENDRUM THOMSONIAE}, volume={34}, ISSN={["0190-4167"]}, DOI={10.1080/01904167.2011.555805}, abstractNote={Clerodendrum thomsoniae plants were grown in silica sand culture to induce and photograph nutritional disorder symptoms. Plants were grown with a complete modified Hoagland's all nitrate solution. The nutrient deficiency treatments were induced with a complete nutrient formula minus one of the nutrients. Boron toxicity was also induced by increasing the element ten times higher than the complete nutrient formula. Reagent grade chemicals and deionized water of 18-mega ohms purity were used to formulate treatment solutions. The plants were automatically irrigated and the solution drained from the bottom of the pot and captured for reuse. The nutrient solutions were completely replaced weekly. Plants were monitored daily to document and photograph sequential series of symptoms as they developed. Typical symptomology of nutrient disorders and critical tissue concentrations are presented. Plants were harvested for nutrient analysis when initial symptoms were expressed. Nutrient deficiency symptoms were described and foliar nutrient concentrations provided.}, number={7}, journal={JOURNAL OF PLANT NUTRITION}, author={Davis, Karen I. and Niedziela, Carl E., Jr. and Reddy, Muchha R. and Whipker, Brian E. and Frantz, Jonathan M.}, year={2011}, pages={1079–1086} }
 @article{krug_whipker_mccall_cleveland_2010, title={GERANIUM LEAF TISSUE NUTRIENT SUFFICIENCY RANGES BY CHRONOLOGICAL AGE}, volume={33}, ISSN={["0190-4167"]}, DOI={10.1080/01904160903470398}, abstractNote={Two cultivars of geranium (Pelargonium × hortorum) were grown under five different fertilizer regimes, 50, 100, 200, 300, or 400 mg·L−1 nitrogen (N). The two cultivars were chosen to represent a dark-colored leaf cultivar, ‘Tango Dark Red’ and a light-colored leaf cultivar, ‘Rocky Mountain Dark Red’. Tissue samples were collected and analyzed for the content of 11 elemental nutrients every two weeks for a period of 12 weeks. The dark-colored leaf cultivar contained higher nutrient concentrations, with the exception of magnesium, sulfur, iron, and copper, than the light-colored leaf cultivar. Compared to concentrations previously published for geraniums, concentration ranges observed in this study were narrower. In addition, this study accounted for differences in concentrations over the entire crop cycle and reflects levels associated with current fertilization practices.}, number={3}, journal={JOURNAL OF PLANT NUTRITION}, author={Krug, Brian A. and Whipker, Brian E. and McCall, Ingram and Cleveland, Brenda}, year={2010}, pages={339–350} }
 @article{krug_whipker_frantz_mccall_2009, title={Characterization of calcium and boron deficiency and the effects of temporal disruption of calcium and boron supply on pansy, petunia, and gerbera plugs}, volume={44}, number={6}, journal={HortScience}, author={Krug, B. A. and Whipker, B. E. and Frantz, J. and McCall, I.}, year={2009}, pages={1566–1572} }
 @article{krug_whipker_mccall_2007, title={Caladium growth control with flurprimidol paclobutrazol, and uniconazole}, volume={17}, number={3}, journal={HortTechnology}, author={Krug, B. A. and Whipker, B. E. and McCall, I.}, year={2007}, pages={368–370} }
 @article{gibson_williams_whipker_nelson_dole_cleveland_walls_2007, title={Foliar symptomology and tissue concentrations of nutrient-deficient vegetative strawflower plants}, volume={38}, ISSN={["0010-3624"]}, DOI={10.1080/00103620701588379}, abstractNote={Abstract Elemental deficiencies of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, copper, zinc, or boron (N, P, K, Ca, Mg, S, Fe, Mn, Cu, Zn, or B) were induced in plants of Florabella Pink strawflower [Bracteantha bracteata (Vent.) A. A. Anderberg]. Rooted stem cuttings were planted in 4.87‐L plastic containers and fertilized with a complete modified Hoagland's solution or this solution minus the element that was to be investigated. Plants were harvested for tissue analyses as well as dry weights when initial foliar symptoms were expressed and later under advanced deficiency symptoms. Deficiency symptoms for all treatments were observed within 7 weeks. The most dramatic expression of foliar symptoms occurred with N (chlorotic lower foliage leading to necrotic margins on the mature leaves), Ca (black necrotic spots on the tips of the young leaves), S (uniform chlorosis of young leaves and recently mature leaves), B (thick, leathery, and deformed young leaves), Fe (uniform yellowish‐green chlorosis on the young leaves), and Zn (brownish‐gray necrosis on the tips of the mature leaves). At the initial stage, only Fe‐deficient plants weighed less than the control, whereas K‐, Ca‐, and Mg‐deficient plants had greater dry weights than plants receiving the complete modified Hoagland's solution (control plants). Dry weights of plants treated with solutions not containing N, P, Ca, S, Cu, or Mn were significantly lower when compared with the control plants under an advanced deficiency. Foliar‐tissue concentration data will assist plant‐tissue analysis laboratories in establishing foliar symptom standards for growers.}, number={17-18}, journal={COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS}, author={Gibson, James L. and Williams, Amy and Whipker, Brian E. and Nelson, Paul V. and Dole, John M. and Cleveland, Brenda and Walls, F. R.}, year={2007}, pages={2279–2294} }
 @article{whipker_mccall_krug_2006, title={Flurprimidol substrate drenches and foliar sprays control growth of 'Blue Champion' exacum}, volume={16}, ISSN={["1063-0198"]}, DOI={10.21273/horttech.16.2.0354}, abstractNote={Flurprimidol was applied as a foliar spray (12.5, 25.0, 37.5, 50.0, or 62.5 mg·L-1) or as a substrate drench (0.015, 0.03, 0.06, 0.12, or 0.24 mg/pot a.i.) to determine its efficacy on `Blue Champion' exacum (Exacum affine). Flurprimidol substrate drenches were more consistent in controlling plant growth than foliar sprays. Substrate drenches of 0.03 mg/pot a.i. or foliar sprays ≥50 mg·L-1 resulted in smaller plant heights and diameters than the untreated control. With the use of flurprimidol, exacum growers have another plant growth regulator (PGR) available to control excessive growth.}, number={2}, journal={HORTTECHNOLOGY}, author={Whipker, BE and McCall, I and Krug, BA}, year={2006}, pages={354–356} }
 @article{krug_whipker_mccall_2006, title={Hyacinth height bulb soaks of control using preplant flurprimidol}, volume={16}, ISSN={["1943-7714"]}, DOI={10.21273/horttech.16.2.0370}, abstractNote={Eight experiments were conducted to develop height control protocols for greenhouse-forced hyacinth (Hyacinthus orientalis) bulbs. `Pink Pearl' hyacinth bulbs were treated with flurprimidol preplant bulb soaks to determine optimal timing of treatment, soak duration, quantity of bulbs that could be treated before the solution lost efficacy, bulb location of solution uptake, and if higher concentrations of flurprimidol can be used to overcome stretch that occurs with extended cold treatment. No difference in height control occurred when bulbs were soaked in flurprimidol the day of, 1 day before, or 7 days before potting; therefore, growers can treat bulbs up to 1 week before potting with no difference in height control. All preplant bulb soak durations of 1, 5, 10, 20, or 40 min controlled plant height. Any soak durations ≥1.3 min resulted in similar height control, which would provide growers with a flexible time frame of 2 to 40 min in which to soak the bulbs. When 1 L of 20 mg·L-1 flurprimidol solution was used repeatedly over 20 batches of five bulbs, solution efficacy was similar from the first batch to the last batch, indicating the soak solution of flurprimidol can be used repeatedly without loss of efficacy. Soak solution temperature was also tested to determine its effect on flurprimidol and paclobutrazol uptake. Temperature of the soak solution (8, 16, or 24 °C) had no effect on flurprimidol and only at a temperature of 8 °C was the efficacy of paclobutrazol lower. Postharvest heights of `Pink Pearl' hyacinths were similar whether only the top, bottom, or the entire bulb was soaked. Control provided by flurprimidol, paclobutrazol, or uniconazole preplant bulb soaks varied among the three hyacinth cultivars Delft Blue, Jan Bos, and Pink Pearl, so growers will have to conduct their own trials to determine optimal cultivar response to preplant bulb soaks. Also, `Pacino' sunflowers (Helianthus annuus) were treated with residual soak solution of flurprimidol to determine if substrate drenches could be used as a disposal method. Fresh and residual solutions of flurprimidol (1.18, 2.37, or 4.73 mg/pot a.i.) applied to `Pacino' sunflowers were similar in their efficacy of controlling height, which would enable growers to avoid disposal problems of residual soak solutions.}, number={2}, journal={HORTTECHNOLOGY}, author={Krug, BA and Whipker, BE and McCall, I}, year={2006}, pages={370–375} }
 @article{krug_whipker_mccall_dole_2006, title={Narcissus response to plant growth regulators}, volume={16}, number={1}, journal={HortTechnology}, author={Krug, B. A. and Whipker, B. E. and McCall, I. and Dole, J. M.}, year={2006}, pages={129–132} }
 @article{krug_whipker_mccall_dole_2005, title={Comparison of flurprimidol to ancymidol, paclobutrazol, and uniconazole for tulip height control}, volume={15}, number={2}, journal={HortTechnology}, author={Krug, B. A. and Whipker, B. E. and McCall, I. and Dole, J. M.}, year={2005}, pages={370–373} }
 @article{krug_whipker_mccall_dole_2005, title={Comparison of flurprimidol to ethephon, paclobutrazol, and uniconazole for hyacinth height control}, volume={15}, number={4}, journal={HortTechnology}, author={Krug, B. A. and Whipker, B. E. and McCall, I. and Dole, J. M.}, year={2005}, pages={872–874} }
 @article{krug_whipker_mccall_2005, title={Flurprimidol is effective at controlling height of 'Star Gazer' oriental lily}, volume={15}, number={2}, journal={HortTechnology}, author={Krug, B. A. and Whipker, B. E. and McCall, I.}, year={2005}, pages={373–376} }
 @article{cavins_whipker_fonteno_2005, title={Timing of PourThru affects pH, electrical conductivity, and leachate volume}, volume={36}, ISSN={["0010-3624"]}, DOI={10.1081/CSS-200059076}, abstractNote={Abstract The time between irrigation and PourThru sampling had not been extensively examined for affects on pH, electrical conductivity (EC), and leachate volume in greenhouse production. A greenhouse study with 16.5 and 19.2 cm wide containers using Fafard 4P and Metro Mix 320 soilless substrates was implemented, and PourThru leachates were extracted and tested for pH, EC, and volume at 15, 30, 60, 120, and 240 minutes after irrigation. Substrates and pot sizes affected PourThru pH and EC; however, timing did not affect these values in this study. The elapsed time between irrigation and sampling affected leachate volumes and mass wetness of the substrates such that values decreased when 120 or 240 minutes elapsed from irrigation to sampling. Based upon the fluctuations in leachate volumes and mass wetness values, it is recommended that 60 minutes elapse from time of irrigation to PourThru sampling. Sixty minutes is sufficient time to allow for nutrient equilibration so the greenhouse crop producers can obtain a representative sample of the plant available nutrient status, yet maintain sufficient moisture status to prevent EC shifts due to moisture content variation leachate volumes from becoming too low. *This research was funded in part by the North Carolina Agricultural Research Service (NCARS), the Fred C. Gloeckner Foundation, Ohio Florist Foundation, and the North Carolina Flower Growers' Association.}, number={11-12}, journal={COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS}, author={Cavins, TJ and Whipker, BE and Fonteno, WC}, year={2005}, pages={1573–1581} }
 @article{whipker_2004, title={Calculating pansy production costs}, volume={49}, number={4}, journal={North Carolina Flower Growers' Bulletin}, author={Whipker, B. E.}, year={2004}, pages={1} }
 @article{krug_whipker_mccall_dole_2004, title={Controlling stem topple of pot tulips}, volume={49}, number={1}, journal={North Carolina Flower Growers' Bulletin}, author={Krug, B. and Whipker, B. E. and McCall, I. and Dole, J.}, year={2004}, pages={14} }
 @article{cavins_whipker_fonteno_2004, title={Establishment of calibration curves for comparing pour-through and saturated media extract nutrient values}, volume={39}, number={7}, journal={HortScience}, author={Cavins, T. J. and Whipker, B. E. and Fonteno, W. C.}, year={2004}, pages={1635–1639} }
 @article{whipker_mccall_gibson_cavins_2004, title={Flurprimidol foliar sprays and substrate drenches control growth of 'Pacino' pot sunflowers}, volume={14}, number={3}, journal={HortTechnology}, author={Whipker, B. E. and McCall, I. and Gibson, J. L. and Cavins, T. J.}, year={2004}, pages={411–414} }
 @article{dole_mccall_whipker_2004, title={National Poinsettia Trial Program highlights}, volume={49}, number={1}, journal={North Carolina Flower Growers' Bulletin}, author={Dole, J. and McCall, I. and Whipker, B. E.}, year={2004}, pages={1} }
 @article{whipker_mccall_2003, title={Comparing paclobutrazols}, volume={48}, number={6}, journal={North Carolina Flower Growers' Bulletin}, author={Whipker, B. E. and McCall, I.}, year={2003}, pages={10} }
 @article{whipker_mccall_gibson_cavins_2003, title={Efficacy of flurprimidol (topflor) on bedding plants}, ISBN={["90-6605-238-4"]}, ISSN={["0567-7572"]}, DOI={10.17660/actahortic.2003.624.58}, number={624}, journal={ELEGANT SCIENCE IN FLORICULTURE}, author={Whipker, BE and McCall, I and Gibson, JL and Cavins, TJ}, year={2003}, pages={413–418} }
 @article{gibson_cavins_greer_whipker_dole_2003, title={Efficacy of plant growth regulators on the growth of Argyranthemum frutescens 'Comet Pink'}, ISBN={["90-6605-238-4"]}, ISSN={["0567-7572"]}, DOI={10.17660/actahortic.2003.624.28}, number={624}, journal={ELEGANT SCIENCE IN FLORICULTURE}, author={Gibson, JL and Cavins, TJ and Greer, L and Whipker, BE and Dole, JM}, year={2003}, pages={213–216} }
 @article{gibson_whipker_2003, title={Efficacy of plant growth regulators on the growth of vigorous osteospermum cultivars}, volume={13}, number={1}, journal={HortTechnology}, author={Gibson, J. L. and Whipker, B. E.}, year={2003}, pages={132–135} }
 @article{krug_whipker_peet_2003, title={FERTCALC -- a fertilizer mixing calculator}, volume={48}, number={6}, journal={North Carolina Flower Growers' Bulletin}, author={Krug, B. A. and Whipker, B. E. and Peet, M.}, year={2003}, pages={8} }
 @article{gibson_whipker_2003, title={Ornamental cabbage quality improved by continual fertilization through center-head coloration}, volume={38}, ISSN={["0018-5345"]}, DOI={10.21273/hortsci.38.7.1381}, abstractNote={Current fertilizer recommendations for ornamental cabbage (Brassica oleracea var. acephala DC.) suggest applying 150 to 300 mg·L-1 N until the initiation of color development, after which fertilization should be reduced or discontinued. Because these plants are actively growing during cool weather when coloration is initiated, nutrient deficiencies may reduce overall plant quality. The objectives of this study were to investigate N to K ratios for plant growth of ornamental cabbage and the effects of continual and discontinued fertilization during the period of coloration. Fertilizing with 150 to 200 mg·L-1 N and 150 to 200 mg·L-1 K produced high-quality plants and provided sufficient tissue concentrations of N and K. Center-head coloration was not inhibited by N concentrations as high as 250 mg·L-1. Ceasing fertilization prior to center-head coloration resulted in the rapid depletion of N, P, and K concentrations in the lower foliage, leading to the appearance of deficiency symptoms and lower leaf loss. Plants were still actively growing as measured by increased shoot mass during the early stages of coloration; therefore, growers should continue to provide a complete analysis fertilizer at N concentrations ≥150 mg·L-1 until market date.}, number={7}, journal={HORTSCIENCE}, author={Gibson, JL and Whipker, BE}, year={2003}, month={Dec}, pages={1381–1384} }
 @article{whipker_2003, title={Ralstonia solanacearum race 3 biovar 2 losses in North Carolina}, volume={48}, number={4}, journal={North Carolina Flower Growers' Bulletin}, author={Whipker, B. E.}, year={2003}, pages={4} }
 @article{gibson_whipker_2001, title={Ornamental cabbage and kale cultivar comparison study: Growth characteristics and response to daminozide and uniconazole foliar sprays}, volume={11}, number={3}, journal={HortTechnology}, author={Gibson, J. L. and Whipker, B. E.}, year={2001}, pages={376–380} }
 @article{gibson_whipker_2001, title={Ornamental cabbage and kale growth responses to daminozide, paclobutrazol, and uniconazole}, volume={11}, number={2}, journal={HortTechnology}, author={Gibson, J. L. and Whipker, B. E.}, year={2001}, pages={226–230} }
 @article{sellmer_adkins_mccall_whipker_2001, title={Pampas grass responses to ancymidol, paclobutrazol, and uniconazole substrate drenches}, volume={11}, ISSN={["1063-0198"]}, DOI={10.21273/horttech.11.2.216}, abstractNote={Plant growth retardant (PGR) substrate drenches (in mg a.i per pot.) of ancymidol at 0.25, 0.5, 1, 2, or 4; paclobutrazol at 1, 2, 4, 8, or 16; and uniconazole at 0.25, 0.5, 1, 2, or 4 (28,350 mg = 1.0 oz) were applied to pampas grass (Cortaderia selloana). Control of height growth during greenhouse forcing and the residual effects on plant growth in the landscape were evaluated. During greenhouse forcing, plant height exhibited a quadratic dose response to paclobutrazol and uniconazole, while ancymidol treated plants exhibited a linear response to increasing dose. All rates of uniconazole resulted in plant heights which were 56% to 75% shorter than the nontreated control, whereas paclobutrazol and ancymidol treatments resulted in 6% to 64% and 5% to 29% shorter plants, respectively. Severe height retardation was evident with {XgtequalX}2 mg uniconazole. When the plants were transplanted and grown in the landscape (24 weeks after the PGR application), all plants treated with ancymidol, paclobutrazol, and {XltequalX}0.5 mg uniconazole exhibited heights similar to the nontreated control, suggesting no residual effects of the PGR for these treatments. Only plants treated with uniconazole at {XgtequalX}1 mg remained shorter than the nontreated control in the landscape. These results demonstrate that plant growth regulators can be effectively and economically applied in the greenhouse production of pampas grass.}, number={2}, journal={HORTTECHNOLOGY}, author={Sellmer, JC and Adkins, CR and McCall, I and Whipker, BE}, year={2001}, pages={216–219} }
 @book{whipker_fonteno_cavins_bailey_2000, title={PourThru nutritional monitoring manual}, publisher={Raleigh, N.C. :  North Carolina State University}, author={Whipker, B. E. and Fonteno, W. C. and Cavins, T. J. and Bailey, D. A.}, year={2000}, pages={40} }
 @article{whipker_dasoju_dosmann_iles_1999, title={Effect of fertilizer concentration on growth of double impatiens}, volume={9}, DOI={10.21273/horttech.9.3.425}, abstractNote={Double impatiens (Impatiens wallerana Hook.) `Blackberry Ice' (variegated-leaf) and `Purple Magic' (green-leaf) were grown on flood benches and irrigated with 50, 100, 200, or 300 mg·L-1 (ppm) N to study the effect of fertility on growth and development. Electrical conductivity (EC) levels at week 9 were similar for both cultivars at each fertilizer rate, except for the 100 mg·L-1 N where EC levels of `Blackberry Ice' were more than double those of `Purple Magic'. This indicated that the nutrient demands were less for `Blackberry Ice' and fertilization rates lower than 100 mg·L-1 N would be required. After nine weeks, plants grown with 100 mg·L-1 N had a 22% larger plant diameter than plants grown with either 50 or 200 mg·L-1 N. Fertilization rates of 50 mg·L-1 N resulted in plants which were covered with a higher percentage of blooms per unit of leaf area, but the plants were smaller. Plant tissue dry weight (leaf, bud, stem, and total) increased to the highest level at 100 mg·L-1 N, then decreased with further increases in fertilization rate. For maximum shoot growth with flood irrigation, growers should apply 100 mg·L-1 N when growing `Purple Magic' double impatiens and a fertilization rate between 50 and 100 mg·L-1 N for `Blackberry Ice'.}, number={3}, journal={HortTechnology}, author={Whipker, B. E. and Dasoju, S. and Dosmann, M. S. and Iles, J. K.}, year={1999}, pages={425} }
 @article{whipker_hammer_1998, title={Comparison of hydroponic solutions for poinsettia nutritional studies}, volume={21}, ISSN={["0190-4167"]}, DOI={10.1080/01904169809365422}, abstractNote={Abstract Poinsettia cultivars Supjibi and Freedom were grown in eight hydroponic solutions to develop a baseline solution for further nutritional studies. Four solutions contained nitrogen (N) from Ca(NO3)2‐4H2O and KNO3 (denoted as ‐NH4) and four contained Ca(NO3)2‐4H2O, KNO3, nitric acid, and NH4NO3 as the N sources (denoted as +NH4). The four ‐NH4 and +NH4 solutions were further divided by an IX or 2X rate of micronutrients [boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn)] (denoted as IX or 2X). A factorial of these four solutions at 2 concentrations (100 mg L1 of N and potassium (K) and 15 mg L1 phosphorus (P), or 300 mg L1 of N and K and 46 mg L‐1 P) was studied. Greater leaf and stem dry weight for both ‘Supjibi’ and ‘Freedom’ was observed in plants grown with the +NH4 solutions, with a larger increase occurring with’ Supjibi’. Leaf NH4‐N content for both cultivars was higher for both the 100 and 300 mg L‐1 N and K fertilization rates when NH4‐N was included. The le...}, number={3}, journal={JOURNAL OF PLANT NUTRITION}, author={Whipker, BE and Hammer, PA}, year={1998}, pages={531–543} }
 @article{whipker_1998, title={Cost of producing ornamental cabbage and kale}, volume={43}, number={4}, journal={North Carolina Flower Growers' Bulletin}, author={Whipker, B. E.}, year={1998}, pages={9} }
 @article{whipker_1998, title={Efficacy of A-Rest, Bonzi, and Sumagic on growth of tuberous-rooted dahlias}, volume={43}, number={2}, journal={North Carolina Flower Growers' Bulletin}, author={Whipker, B. E.}, year={1998}, pages={12} }
 @article{whipker_hammer_1998, title={Nutrient uptake in vegetative poinsettias grown with two fertilizer concentrations and two pinching dates}, volume={21}, ISSN={["0190-4167"]}, DOI={10.1080/01904169809365423}, abstractNote={Abstract The effects of varying fertilizer application rates [100–15–100 or 300–46–300 mg L‐1 of nitrogen (N)‐phosphorus (P)‐potassium (K)] and pinching dates on nutrient uptake patterns of poinsettias were studied. During the first seven weeks after potting, varying the N‐P‐K fertilization rate from 100–15–100 to 300–46–300 mg L‐1 N‐P‐K had no effect on plant height, dry weight, nutrient concentration, or nutrient content of poinsettias. The uptake ratios for NO3‐N, K, calcium (Ca), and magnesium (Mg) all were 60% and >70%, respectively, for NH4‐N and P at the 100 mg L"1 N and K fertilization rate indicated the plants utilized a higher percentage of the available NH4‐N and P, indicating that an application rate >18 mg L‐1 NH4‐N and >15 mg L‐1 P w...}, number={3}, journal={JOURNAL OF PLANT NUTRITION}, author={Whipker, BE and Hammer, PA}, year={1998}, pages={545–559} }
 @article{whipker_dasoju_dosmann_iles_1998, title={Research report: F ertilizer rate effects on growth of variegated and green-leaved double Impatiens}, volume={43}, number={5}, journal={North Carolina Flower Growers' Bulletin}, author={Whipker, B. E. and Dasoju, S. and Dosmann, M. S. and Iles, J. K.}, year={1998}, pages={15} }