@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{durand_jackson_fonteno_michel_2023, title={Particle size distribution of growing media constituents using dynamic image analysis: Parametrization and comparison to sieving}, ISSN={["1435-0661"]}, DOI={10.1002/saj2.20518}, abstractNote={Abstract Growing media constituents have heterogeneous particle size and shape, and their physical properties are partly related to them. Particle size distribution is usually analyzed through sieving process, segregating the particles by their width. However, sieving techniques are best describing more granular shapes and are not as reliable for materials exhibiting large varieties of shapes, like growing media constituents. A dynamic image analysis has been conducted for a multidimensional characterization of particle size distribution of several growing media constituents (white and black peats, pine bark, coir, wood fiber, and perlite), from particles that were segregated and dispersed in water. Diameters describing individual particle width and length were analyzed, then compared to particle size distribution obtained by dry and wet sieving methods. This work suggests the relevance of two parameters, Feret MAX and Chord MIN diameters for assessing particle length and width, respectively. They largely varied among the growing media constituents, confirming their non‐spherical (i.e., elongated) shapes, demonstrating the advantages of using dynamic image analysis tools over traditional sieving methods. Furthermore, large differences in particle size distribution were also observed between dynamic image analysis and sieving procedures, with a finer distribution for dynamic image analysis. The discrepancies observed between methodologies were discussed (particle segregation, distribution weighing, etc.), while describing in details methodological limitations of dynamic image analysis.}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, author={Durand, Stan and Jackson, Brian E. and Fonteno, William C. and Michel, Jean-Charles}, year={2023}, month={Apr} }
 @article{bartley iii_yap_jackson_fonteno_boyette_chaves-cordoba_2023, title={Quantifying the Sorptive Behavior of Traditional Horticultural Substrate Components Based on Initial Hydraulic Conditioning}, volume={58}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI16698-22}, abstractNote={The ability of a substrate component (organic or inorganic) to capture and retain water (hydration and wettability) is important to investigate and promote water-use–efficient practices. Many factors may play a role in the wettability of the material, including the processing of the material and its initial handling. The goal of this experiment was to determine the effect of moisture content (MC) on the sorptive behavior of substrates after an initial and secondary hydration cycle. Coir, peat, and aged pine bark were evaluated at a 33%, 50%, and 66% MC by weight. At all moisture levels, coir and bark were minimally affected by MC or the initial hydration cycle. Peat was the most vulnerable to changes in sorptive behavior as a result of wetting and drying cycles. After a wetting and drying cycle, the maximum volumetric water content of peat from surface irrigation was reduced 21.5% (volumetrically), more than three times any other treatment. The hydration efficiency of peat was improved when blended with as little as 15% coir. These experiments provide evidence that MC and initial handling of the substrate can lead to differences in initial water use efficiency.}, number={1}, journal={HORTSCIENCE}, author={Bartley III, Paul C. and Yap, Ted C. and Jackson, Brian E. and Fonteno, William C. and Boyette, Michael D. and Chaves-Cordoba, Bernardo}, year={2023}, month={Jan}, pages={79–83} }
 @article{durand_jackson_fonteno_michel_2023, title={Quantitative Description and Classification of Growing Media Particle Morphology through Dynamic Image Analysis}, volume={13}, ISSN={["2077-0472"]}, DOI={10.3390/agriculture13020396}, abstractNote={The physical properties of growing media are dependent on the morphological characteristics of the particles composing them. Thus, their characteristics can be more precisely altered for specific purposes by a better morphological design of materials to optimize the use of raw materials and increase water efficiency. There are many references on the relationship between basic particle size and physical properties, but the arrangement of the particles and the resulting physical properties are also affected by the shape of the particles. Growing media have seldom been characterized by shape criteria and, therefore, their influence remains unknown. A dynamic image analyzer, the QicPic device, was used to assess particle shape and size for a wide diversity of growing media constituents. As well as FeretMAX and ChordMIN diameters describing individual particle length and width, respectively, individual particle shape was analyzed in terms of several descriptors (aspect ratio, circularity, roundness, and convexity). A classification was established to discern different particle shapes and all materials were described accordingly. Correlations between particle morphology descriptors were reported, showing that the greater the particle length, the smaller the width/length ratio, circularity, roundness, and convexity. Circularity, roundness, particle length, and its associated relative span were identified as the most relevant parameters describing materials’ morphology. This work shows a large diversity in particle morphology of growing media constituents, which were categorized into four classes of materials. Three classes were mainly described according to their particle shapes, with a decreasing elongation and an increasing circularity, roundness, and convexity: (1) fine and coarse wood and coir fibers; (2) all Sphagnum white peats, milled or sod; and (3) black peats, sedge peat, coir pith, fresh and composted pine bark, green waste compost, and perlite. A fourth class was represented by coir medium (mixing pith and fibers) and was above all characterized by high diversity in particle length. These findings extend the characterization of the materials for a more thorough evaluation of the links between particle morphology and physical properties.}, number={2}, journal={AGRICULTURE-BASEL}, author={Durand, Stan and Jackson, Brian E. and Fonteno, William C. and Michel, Jean-Charles}, year={2023}, month={Feb} }
 @article{fields_owen jr_lamm_altland_jackson_oki_samtani_zheng_criscione_2023, title={Surveying North American Specialty Crop Growers' Current Use of Soilless Substrates and Future Research and Education Needs}, volume={13}, ISSN={["2077-0472"]}, DOI={10.3390/agriculture13091727}, abstractNote={Many specialty crop growers are transitioning high-value crops from in-ground production to soilless culture due to the diminishing availability of fumigants, increasing pest pressure, extreme weather, and the need for flexible production practices. The objective of this study was to determine the research and educational needs of specialty crop growers who are transitioning to soilless substrates. North American growers were surveyed using an online instrument that incorporated Likert-type statement matrices, open-ended questions, and demographic questions. Additionally, two virtually led focus groups were conducted to further expand upon the quantitative findings with descriptive data. Respondents indicated the most important factors in considering whether to adopt soilless substrates were improving, managing, and reducing overall plant quality, disease management, and crop loss, respectively. The most important research needs were understanding the effects of substrates on crop quality and uniformity, fertilizer management, and economic costs and benefits/return on investment. In both the grower survey and focus groups, crop quality and uniformity were among the highest-scored responses. Food safety, disease and pest management, consumer perception, substrate disposal-related issues, transportation, and return-on-investment were also identified as important factors when considering soilless substrates.}, number={9}, journal={AGRICULTURE-BASEL}, author={Fields, Jeb S. and Owen Jr, James S. and Lamm, Alexa and Altland, James and Jackson, Brian and Oki, Lorence and Samtani, Jayesh B. and Zheng, Youbin and Criscione, Kristopher S.}, year={2023}, month={Sep} }
 @article{woznicki_jackson_sonsteby_kusnierek_2023, title={Wood Fiber from Norway Spruce-A Stand-Alone Growing Medium for Hydroponic Strawberry Production}, volume={9}, ISSN={["2311-7524"]}, DOI={10.3390/horticulturae9070815}, abstractNote={There is an increased interest in the hydroponic production of strawberries in protected cultivation systems, and it is, therefore, urgent to develop new, more sustainable growing media alternatives. This study investigated the physical properties of wood fiber produced from Norway spruce (Picea abies (L.) H. Karst.) and peat:wood fiber substrate blends as well as the performance of the wood fiber in comparison to the industry standards, i.e., peat and coconut coir in the cultivation of hydroponic strawberry. Tray plants of the June-bearing strawberry (Fragaria × ananassa Duch.) cultivar ‘Malling Centenary’ were transplanted into five different growing media: a peat (80%) and perlite (20%) mixture, stand-alone (100%) coconut coir and three stand-alone (100%) Norway spruce wood fiber substrates (including coarse textured fibers with compact and loose packing density and compacted fine-textured fibers). Ripe strawberries were harvested and registered throughout the production season. The overall marketable yield was comparable across all the tested growing media; however, after 4 weeks of harvest, both coarse wood fiber and fine wood fiber showed better fruiting performance than the peat-perlite mixture. A trend for earlier berry maturation was observed for all wood fiber-based substrates. Plant parameters recorded after the end of production showed that plant height, number of leaves, and biomass production were higher in coarse wood fiber than in the peat-perlite mixture. Moreover, plants grown in wood fiber-based substrates had less unripe berries and flowers not harvested in comparison to both the peat and coir treatments.}, number={7}, journal={HORTICULTURAE}, author={Woznicki, Tomasz and Jackson, Brian E. and Sonsteby, Anita and Kusnierek, Krzysztof}, year={2023}, month={Jul} }
 @misc{bartley_fonteno_jackson_2022, title={A Review and Analysis of Horticultural Substrate Characterization by Sieve Analysis}, volume={57}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI16583-22}, abstractNote={The physical, hydrological, and physico-chemical properties of horticultural substrates are influenced by particle shape and size. Sieve analysis has been the predominate method used to characterize the particle size distribution of horticultural substrates. However, the literature shows a diversity of techniques and procedures. The effects of agitation time and sample size on particle size distributions of soilless substrates were evaluated for several measures of sieve analysis, including sieve rate (a calculation of the percentage of material passed for each unit time of agitation), distribution median, sd, mass relative span, skewness, and kurtosis. To obtain the standard sieve rate (0.1%/min), pine bark, peat, perlite, and coir required agitation times of 4 minutes and 47 seconds, 7 minutes and 18 seconds, 10 minutes, and 11 minutes, respectively. However, there was concern that unwanted particle breakdown may occur during the particle size analysis of some materials. Therefore, a sieve rate (0.15%/min) for more friable materials was also determined. As a result, the endpoint of sieving was reached sooner for pine bark, peat, perlite, and coir, at 3 minutes and 10 seconds, 4 minutes and 42 seconds, 5 minutes and 14 seconds, and 6 minutes and 24 seconds, respectively. Increasing agitation time resulted in decreased distribution median, sd, and skewness for all materials. Sample sizes half and twice the volume of the recommended initial volume sieved did not change particle size distributions. For more precise characterization of particle size distributions when characterizing substrate components, agitation times and sample sizes should be specified for each material or collectively for all materials to ensure consistency and allow comparisons between results.}, number={6}, journal={HORTSCIENCE}, author={Bartley, Paul C., III and Fonteno, William C. and Jackson, Brian E.}, year={2022}, month={Jun}, pages={715–725} }
 @article{dickson_helms_jackson_machesney_lee_2022, title={Evaluation of Peat Blended with Pine Wood Components for Effects on Substrate Physical Properties, Nitrogen Immobilization, and Growth of Petunia (Petunia x hybrida Vilm.-Andr.)}, volume={57}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI16177-21}, abstractNote={The first objective was to evaluate wood components for differences in nitrogen (N) immobilization and effects on substrate physical properties. The second objective was to evaluate peat substrates amended with pine wood components for effects on plant growth, shoot tissue N, and fertigation practices during production. Substrates consisted of a coarse sphagnum peat blended with four types of processed pine wood at rates of 15%, 30%, 45%, and 60% (by volume). For comparison, peat was also blended with an aged pine bark, perlite, and coconut coir. Nitrogen immobilization was measured for individual components, except perlite. Individual components and blended substrates were evaluated for particle size distribution, total air porosity, container capacity, and dry bulk density. In a greenhouse experiment, petunia (Petunia × hybrida Vilm.-Andr.) were grown in hanging basket containers with each substrate blend as well as 100% peat, which served as a nonblended control substrate, and fertilized at each irrigation with 200 mg·L−1 N. Blended component and blend percent interacted in effects on all measured substrate physical properties; however, physical properties of all substrate blends were considered adequate for horticultural purposes. In the laboratory, pine bark immobilized 9% of total N supplied, whereas the remaining pine wood components immobilized <5% of total N. In the greenhouse experiment, blend component influenced shoot growth and flowering, which were greatest for petunia grown in 100% peat. Increasing the blend percent of all components decreased shoot growth and flowering with all blended components. Blended substrates had minimal effects on number of fertigation events, and substrate treatments differed by a maximum of three fertigation events per container over a 56-d period. This study illustrates the challenges of measuring N immobilization because results from the laboratory were not consistent with plant performance in the greenhouse. Increasing blends of each substrate (including perlite) were also observed to interact with fertigation practices and therefore applied N, tissue N, shoot dry weight, and total N uptake. As a practical conclusion from this study, peat incorporated with 60% wood fiber increased the risk of reduced plant growth and N uptake, but this risk was lower as the blend percentage decreased. In addition, other analytical methods to test N immobilization, such as microbial respiration, should be further explored.}, number={2}, journal={HORTSCIENCE}, author={Dickson, Ryan W. and Helms, Kalyn M. and Jackson, Brian E. and Machesney, Leala M. and Lee, Jung Ae}, year={2022}, month={Feb}, pages={304–311} }
 @article{bartley_amoozegar_fonteno_jackson_2022, title={Particle Densities of Horticultural Substrates}, volume={57}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI16319-21}, abstractNote={The heterogeneity of horticultural substrates makes basic physical characteristics, such as total porosity and particle density, difficult to estimate. Due to the material source, inclusion of occluded pores, and hydrophobicity, particle density values reported from using liquid pyknometry, vary widely. Gas pycnometry was used to determine the particle density of coir, peat, perlite, pine bark, and wood substrates. Further precision was examined by gas species and separation by particle size. The calculated particle densities for each material determined by He, N2, and air were relatively constant and varied little despite the species of gas used. Particle size affected the measured particle density of perlite and pine bark but was minimal with coir, peat, and wood. Reducing the particle size removed more occluded pores and the measured particle density increased. Given the small variability, the use of particle density values obtained by gas pycnometry provides repeatable, precise measurements of substrate material total porosity.}, number={3}, journal={HORTSCIENCE}, author={Bartley, Paul C., III and Amoozegar, Aziz and Fonteno, William C. and Jackson, Brian E.}, year={2022}, month={Mar}, pages={379–383} }
 @article{nguyen_kraska_winkler_aydinlik_jackson_pude_2022, title={Primary Mechanical Modification to Improve Performance of Miscanthus as Stand-Alone Growing Substrates}, volume={12}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy12020420}, abstractNote={Selecting proper mechanical processing can improve performance of miscanthus substrates. We studied the effects of mechanical processing methods on substrate morphology, hydrological properties, pH, and nitrogen immobilization. Miscanthus × giganteus biomass was processed into field chips (FC, forage harvester), shreds (S5, mechanical fraying machine through a 5-mm screen) and chips (C15, C10, C5 and C3, hammermill with screen size of 15, 10, 5, or 3 mm). Processed miscanthus materials were also tested as propagation substrates for Chinese cabbage seedlings. Results showed that particle size distribution of miscanthus substrates formed four groups in ascending order of particle size: C3 < C5 < (C10, C15, S5) < FC. The finer miscanthus substrates had higher water holding capacity following the same groupings in particle size. The hydrophobicity of processed miscanthus was low and reversible, with the increasing order of risk as C3 < C5 < C10, C15 < S5, FC. All miscanthus substrates had similar and low pH buffering capacity. Nitrogen immobilization was similar among miscanthus substrates. The seedlings in miscanthus substrates had similar germination rates but a lower biomass compared to those grown in peat and coir. Primary mechanical modification of miscanthus offers opportunities for different sizes of substrate materials with few changes to the physical or chemical properties tested in this work.}, number={2}, journal={AGRONOMY-BASEL}, author={Nguyen, Van T. H. and Kraska, Thorsten and Winkler, Winona and Aydinlik, Sercan and Jackson, Brian E. and Pude, Ralf}, year={2022}, month={Feb} }
 @article{poleatewich_michaud_jackson_krause_degenring_2022, title={The Effect of Peat Moss Amended with Three Engineered Wood Substrate Components on Suppression of Damping-Off Caused by Rhizoctonia solani}, volume={12}, ISSN={["2077-0472"]}, DOI={10.3390/agriculture12122092}, abstractNote={The use of wood-derived materials in soilless substrates for horticultural crop production is increasing; however, there is little information about the effects of wood on the incidence and severity of soilborne diseases of container-grown plants. The objectives of this research were to compare three differently processed wood substrate components blended with sphagnum peat and to investigate the effect of the peat:wood blend ratio on damping-off disease caused by Rhizoctonia solani using radish as a model system. In objective one, raw sphagnum peat was blended with three types of processed pine wood, screw-extruded, twin disc-refined, and hammer-milled, at a volumetric ratio of 70:30 and compared to a 70:30 peat:perlite mix. Radish plants grown in the hammer-milled wood and disc-refined wood had significantly lower damping-off disease severity compared to plants grown in the peat–perlite control. In objective two, sphagnum peat was blended with the three types of processed wood at a volumetric ratio of 90:10, 80:20, and 70:30 and compared to a 70:30 peat–perlite mix. The effect of the blend ratio varied by wood processing type. Higher percentages of Forest Gold and pine tree substrate resulted in lower disease severity. In both objectives, radish plants grown in any of the substrate treatments containing wood infested with R. solani tended to have lower disease severity compared to plants in the control. Results of this study indicate that the blending of processed pine wood-derived components into peat may enhance the natural suppression of damping-off disease of radish. Further research is needed to elucidate the mode of action of wood-derived materials on disease suppression in container-grown crops and to study the effects for other plant pathogens and crop species.}, number={12}, journal={AGRICULTURE-BASEL}, author={Poleatewich, Anissa and Michaud, Isobel and Jackson, Brian and Krause, Matthew and DeGenring, Liza}, year={2022}, month={Dec} }
 @article{li_hu_li_truong_li_lin_naik_xiang_jackson_kuo_et al._2021, title={Enhancing the multi-functional properties of renewable lignin carbon fibers via defining the structure-property relationship using different biomass feedstocks}, volume={23}, ISSN={["1463-9270"]}, DOI={10.1039/d0gc03828h}, abstractNote={Lignin from different biomass feedstock has been explored to make quality carbon fiber. The mechanistic study revealed the β-O-4 linkages of lignin linearly correlated to both mechanical and electroconductive performance of carbon fibers.}, number={10}, journal={GREEN CHEMISTRY}, author={Li, Qiang and Hu, Cheng and Li, Mengjie and Truong, Phuc and Li, Jinghao and Lin, Hao-Sheng and Naik, Mandar T. and Xiang, Sisi and Jackson, Brian E. and Kuo, Winson and et al.}, year={2021}, month={May}, pages={3725–3739} }
 @article{schulker_jackson_fonteno_heitman_albano_2021, title={Exploring Substrate Water Capture in Common Greenhouse Substrates through Preconditioning and Irrigation Pulsing Techniques}, volume={11}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy11071355}, abstractNote={Particles in a substrate create a network of pore pathways for water to move through, with size and shape determining the efficacy of these channels. Reduced particle size diversity can lead to increased leachate, poor substrate hydration, and an inefficient irrigation practice. This research examined the hydration characteristics of three greenhouse substrate components at three preconditioned initial moisture contents using subirrigation under five different irrigation durations and three water depths (2 mm, 20 mm, and 35 mm). Sphagnum peatmoss, coconut coir, and aged pine bark were tested at 67%, 50%, and 33% initial moisture (by weight). The objectives were to determine the impact of varying irrigation event durations (5, 10, 20, 30, 60 min) over a 60-min period, and the further influence of water depth and initial moisture, on the water capture abilities of peat, coir, and pine bark. The number of irrigation events depended on the irrigation event time of that experimental unit divided by the total time of 60 min, varying from 12, 6, 3, 2, and 1 event. Hydration efficiency was influenced by initial moisture content (IMC), water depth, pulsing duration, and inherent substrate characteristics (hydrophobicity/hydrophilicity). Initial MC had the largest impact on peat, regardless of water level or irrigation duration. Lower IMCs increased the hydrophobic response of peat, further reducing the amount of water the substrate was able to absorb. Pine bark had a 5–10% decrease in initial hydration between 67%, 50%, and 33% IMC, while coir’s hydrophilic nature reduced any IMC affects. At 50% IMC or less, coir had the highest volumetric water content (VWC) across all substrates, pulsing durations, and water depths. Water depth was found to increase initial hydration and final hydration 6–8% across all substrates. These three materials had altered and varied water capture responses depending on the combination of treatments employed. This work demonstrated the effects of intensity and exposure on substrates and the need for more integrated research for improving water use efficiency on container crops.}, number={7}, journal={AGRONOMY-BASEL}, author={Schulker, Brian A. and Jackson, Brian E. and Fonteno, William C. and Heitman, Joshua L. and Albano, Joseph P.}, year={2021}, month={Jul} }
 @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{suchoff_jackson_gunter_schultheis_louws_2021, title={Non-destructive characterization of grafted tomato root systems using the mini-horhizotron}, volume={1302}, ISSN={["2406-6168"]}, url={https://publons.com/wos-op/publon/56007334/}, DOI={10.17660/ActaHortic.2021.1302.28}, journal={II INTERNATIONAL SYMPOSIUM ON VEGETABLE GRAFTING}, author={Suchoff, D. H. and Jackson, B. E. and Gunter, C. C. and Schultheis, J. R. and Louws, F. J.}, year={2021}, pages={209–214} }
 @article{durand_jackson_fonteno_michel_2021, title={The Use of Wood Fiber for Reducing Risks of Hydrophobicity in Peat-Based Substrates}, volume={11}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy11050907}, abstractNote={Peat substrates are well known to become hydrophobic during desiccation, thus degrading their water retention properties. Synthetic wetting agents are commonly incorporated to limit the risk of hydrophobicity, but substrates companies are searching for more sustainable alternatives. To that end, the effect of wood fiber addition in peat-based mixes was measured using contact angles and hydration curves. The study was carried out on two raw materials (white milled peat and wood fiber) and binary mixes. The results showed a shift from hydrophilic to more hydrophobic character with a decrease in the ability to rewet of peat-based substrates in relation to the intensity of drying, whereas wood fiber remained hydrophilic. Increasing wood fiber content in peat-based mixes improved the rehydration efficiency, but with a lower intensity of that measured with synthetic wetting agent addition. Our results highlighted the hydrophilic nature of wood fiber and demonstrated an additional benefit of wood fiber use in peat-based growing media.}, number={5}, journal={AGRONOMY-BASEL}, author={Durand, Stan and Jackson, Brian E. and Fonteno, William C. and Michel, Jean-Charles}, year={2021}, month={May} }
 @article{michel_jackson_fonteno_2021, title={The use of coir for reducing risks of peat-based substrate hydrophobicity}, volume={1305}, ISSN={["2406-6168"]}, DOI={10.17660/ActaHortic.2021.1305.59}, abstractNote={The wettability of peat, coir and peat:coir mixes (90:10, 80:20 and 70:30 v v-1) were analyzed from contact angle measurements and hydration efficiency tests, and also compared to the effects of wetting agents. Results showed a change from a hydrophilic to an increasing hydrophobic character of peat in relation to the intensity of drying, whereas coir remained hydrophilic. Although its influence is lower than those measured with wetting agent, coir addition in peat-based substrates improved the ability to rewet (i.e. to reduce the risks of hydrophobicity occurring during drying).}, journal={III INTERNATIONAL SYMPOSIUM ON GROWING MEDIA, COMPOSTING AND SUBSTRATE ANALYSIS}, author={Michel, J. C. and Jackson, B. E. and Fonteno, W. C.}, year={2021}, pages={449–454} }
 @article{schulker_jackson_fonteno_heitman_albano_2020, title={Comparison of Water Capture Efficiency through Two Irrigation Techniques of Three Common Greenhouse Soilless Substrate Components}, volume={10}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy10091389}, abstractNote={Substrate wettability is an important factor in determining effective and efficient irrigation techniques for container-grown crops. Reduced substrate wettability can lead to lower substrate water capture, excessive leaching and poor plant growth. This research examined substrate water capture using surface and subirrigation under three initial moisture contents (IMC). Sphagnum peat moss, coconut coir, and pine bark were tested at IMCs of 67% 50%, and 33%. Substrate water capture was influenced by both IMC and irrigation technique. Surface irrigation increased the water capture of coir and peat, regardless of IMC, whereas IMC influenced pine bark water capture more than irrigation method. Surface-irrigated coir at or above 50% IMC provided the greatest water capture across all treatments. The first irrigation had the highest capture rate compared to all other events combined. Container capacities of pine bark and coir were unaffected by IMC and irrigation type, but the CC of peat was less by ~ 40% volumetrically under low IMC conditions. Coir, had the greatest ability to capture water, followed by pine bark and peat, respectively. Moisture content, irrigation type and component selection all influence the water capture efficiency of a container substrate.}, number={9}, journal={AGRONOMY-BASEL}, author={Schulker, Brian A. and Jackson, Brian E. and Fonteno, William C. and Heitman, Joshua L. and Albano, Joseph P.}, year={2020}, month={Sep} }
 @article{shreckhise_owen_eick_niemiera_altland_jackson_2020, title={Dolomite and Micronutrient Fertilizer Affect Phosphorus Fate When Growing Crape Myrtle in Pine Bark}, volume={55}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI14558-20}, abstractNote={Soilless substrates are routinely amended with dolomite and sulfate-based micronutrients to improve fertility, but the effect of these amendments on phosphorous (P) in substrate pore-water during containerized crop production is poorly understood. The objectives of this research were as follows: compare the effects of dolomite and sulfate-based micronutrient amendments on total P (TP), total dissolved P (TDP), orthophosphate P (OP), and particulate P (PP; TP − TDP) concentrations in pour-through extracts; to model saturated solid phases in substrate pore-water using Visual MINTEQ; and to assess the effects of dolomite and micronutrient amendments on growth and subsequent P uptake efficiency (PUE) of Lagerstroemia L. ‘Natchez’ (crape myrtle) potted in pine bark. Containerized crape myrtle were grown in a greenhouse for 93 days in a 100% pine bark substrate containing a polymer-coated 19N–2.6P–10.8K controlled-release fertilizer (CRF) and one of four substrate amendment treatments: no dolomite or micronutrients (control), 2.97 kg·m−3 dolomite (FL); 0.89 kg·m−3 micronutrients (FM); or both dolomite and micronutrients (FLM). Pour-through extracts were collected approximately weekly and fractioned to measure pore-water TP, TDP, and OP and to calculate PP. Particulate P concentrations in pour-through extracts were generally unaffected by amendments. Relative to the control, amending pine bark with FLM reduced water-extractable OP, TDP, and TP concentrations by ≈56%, had no effect on P uptake efficiency, and resulted in 34% higher total dry weight (TDW) of crape myrtle. The FM substrate had effects similar to those of FLM on plant TDW and PUE, and FM reduced pore-water OP, TDP, and TP concentrations by 32% to 36% compared with the control. Crape myrtle grown in FL had 28% lower TDW but pour-through OP, TDP, and TP concentrations were similar to those of the control. Chemical conditions in FLM were favorable for precipitation of manganese hydrogen phosphate (MnHPO4), which may have contributed to lower water-extractable P concentrations in this treatment. This research suggests that amending pine bark substrate with dolomite and a sulfate-based micronutrient fertilizer should be considered a best management practice for nursery crop production.}, number={6}, journal={HORTSCIENCE}, author={Shreckhise, Jacob H. and Owen, James S., Jr. and Eick, Matthew J. and Niemiera, Alexander X. and Altland, James E. and Jackson, Brian E.}, year={2020}, month={Jun}, pages={832–840} }
 @article{harris_dickson_fisher_jackson_poleatewich_2020, title={Evaluating Peat Substrates Amended with Pine Wood Fiber for Nitrogen Immobilization and Effects on Plant Performance with Container-grown Petunia}, volume={30}, ISSN={["1943-7714"]}, DOI={10.21273/HORTTECH04526-19}, abstractNote={Pine (Pinus sp.) wood products have potential to immobilize fertilizer nitrogen (N) and influence plant growth when used in soilless substrates for the production of containerized floriculture crops. Peat substrate was amended with (by volume) 30% pine wood fiber (peat:fiber) during a production phase with fertigation and a simulated consumer retail phase with clear-water irrigation using container-grown ‘Supertunia Vista Bubblegum’ petunia (Petunia ×hybrida). The objective was to evaluate substrate effects on substrate and plant tissue nutrient level and plant growth, with an emphasis on evaluating N immobilization from wood product amendments. Substrates consisting of peat amended with hammer-milled pine wood (peat:wood) or coconut (Cocos nucifera) coir (peat:coir) were used for comparison, and a 100% peat substrate (peat) served as a control. In Expt. 1, amending peat with pine wood fiber had no effect on leaf SPAD chlorophyll index, shoot growth, plant height and width, substrate N, or percent shoot tissue N at the end-of-production. In Expt. 2, plants grown in peat:fiber had reduced flower number, plant height and width, and shoot growth compared with plants grown in the 100% peat control. However, petunia grown in peat:fiber substrates maintained dark-green foliage with high leaf SPAD chlorophyll index values (≥44.4) and ≥45 flowers/plant, and therefore were considered marketable plants. During the production phase in both Expts. 1 and 2, N concentrations remained within the target range for petunia in both the shoot tissue and root-zone for all substrates. In addition, there was no statistical evidence of N immobilization for any substrate blend for either of the N drawdown procedures. In both Expts. 1 and 2, root-zone nutrients became depleted during the consumer phase when irrigation was with clear water (no fertilizer), and petunia developed uniform symptoms of leaf chlorosis and N deficiency. Results of this study indicate that peat amended with 30% pine wood fiber, hammer-milled pine wood, and coconut can be used for production of containerized petunia with minimal effects on plant growth or need to adjust the fertilizer program. However, increasing pine wood to >30% of the substrate volume may require growers to increase fertilization and adjust irrigation practices to compensate for greater risk of N immobilization and changes in substrate physical properties.}, number={1}, journal={HORTTECHNOLOGY}, author={Harris, Crysta N. and Dickson, Ryan W. and Fisher, Paul R. and Jackson, Brian E. and Poleatewich, Anissa M.}, year={2020}, month={Feb}, pages={107–116} }
 @article{hembree_ranney_lynch_jackson_2020, title={Identification, Genome Sizes, and Ploidy of Deutzia}, volume={145}, ISSN={["2327-9788"]}, DOI={10.21273/JASHS04779-19}, abstractNote={The genus Deutzia, in the Hydrangeaceae family, includes ≈60 species that range in ploidy from diploid (2x) to tetradecaploid (14x). There have been extensive breeding efforts for Deutzia, but this has been limited to a few parental species. Although there have been numerous studies of the cytogenetics of some species of Deutzia, the ploidy level of many species remains unknown, and there are few cytogenetic data available for Deutzia hybrids and cultivars. The purpose of this study was to validate the identification and determine the genome sizes and ploidy of a diverse collection of Deutzia species and hybrids using cytology and flow cytometry. Accessions were identified using the most current taxonomic key and voucher specimens were deposited for each at the North Carolina State University herbarium. Corrected and updated species names are provided for all cultivars and accessions studied. Traditional cytology was performed for roots of representative taxa to calibrate the genome size with the ploidy level. The genome size and estimated ploidy were determined for 43 accessions using flow cytometry. Ploidy levels were reported for the first time for three species of Deutzia including D. calycosa (2n = 4x = 52), D. paniculata (2n = 4x = 52), and D. glauca (2n = 12x = 156). The base and monoploid genome size (1Cx) were somewhat variable and ranged from 1.20 to 2.05 pg. No anisoploid hybrids were documented, suggesting the presence of an interploid block. The information produced from this study are beneficial to future curation, research, development, and improvement of this genus with corrected nomenclature and clone-specific data regarding cytogenetics.}, number={2}, journal={JOURNAL OF THE AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE}, author={Hembree, William G. and Ranney, Thomas G. and Lynch, Nathan P. and Jackson, Brian E.}, year={2020}, month={Mar}, pages={88–94} }
 @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{bertucci_bartley_jennings_monks_jackson_2020, title={Quantification of palmer amaranth seed number using a computerized particle analyzer}, volume={5}, ISSN={["2471-9625"]}, DOI={10.1002/ael2.20003}, abstractNote={We evaluated the accuracy of a computerized particle analyzer (CPA) for high‐throughput counting of Palmer amaranth (Amaranthus palmeri S. Watson) seeds and subsequently used the CPA to verify the accuracy of two subsampling methods for estimation of Palmer amaranth seed production. To determine accuracy of the CPA, 55 hand‐counted samples, ranging from 500 to 5000 Palmer amaranth seeds, were drawn from field samples and counted with the CPA. The relationship between hand and CPA seed counts was described by a linear model (R2 = 0.99) with a slope of 0.987 and a y‐intercept of 3.49. Thus, very little discrepancy exists between seed counts conducted by hand or the CPA. Additionally, two published methods for estimation of Palmer amaranth seed production were compared to the CPA and proven to be highly accurate. We conclude from these findings that the CPA offers a high‐throughput alternative for weed scientists who frequently count large quantities of seed.}, number={1}, journal={AGRICULTURAL & ENVIRONMENTAL LETTERS}, author={Bertucci, Matthew B. and Bartley, Paul C., III and Jennings, Katherine M. and Monks, David W. and Jackson, Brian E.}, year={2020} }
 @article{fields_fonteno_jackson_heitman_owen_2020, title={The Use of Dewpoint Hygrometry to Measure Low Water Potentials in Soilless Substrate Components and Composites}, volume={10}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy10091393}, abstractNote={Plant water availability in soilless substrates is an important management consideration to maximize water efficiency for containerized crops. Changes in the characteristics (i.e., shrink) of these substrates at low water potential (<−1.0 MPa) when using a conventional pressure plate-base can reduce hydraulic connectivity between the plate and the substrate sample resulting in inaccurate measures of water retention. Soilless substrate components Sphagnum peatmoss, coconut coir, aged pine bark, shredded pine wood, pine wood chips, and two substrate composites were tested to determine the range of volumetric water content (VWC) of surface-bound water at water potentials between −1.0 to −2.0 MPa. Substrate water potentials were measured utilizing dewpoint hygrometry. The VWC for all components or composites was between 5% and 14%. These results were considerably lower compared to previous research (25% to 35% VWC) utilizing conventional pressure plate extraction techniques. This suggests that pressure plate measurements may overestimate this surface-bound water which is generally considered unavailable for plant uptake. This would result in underestimating available water by as much as 50%.}, number={9}, journal={AGRONOMY-BASEL}, author={Fields, Jeb S. and Fonteno, William C. and Jackson, Brian E. and Heitman, Joshua L. and Owen, James S., Jr.}, year={2020}, month={Sep} }
 @article{hembree_ranney_jackson_weathington_2019, title={Cytogenetics, Ploidy, and Genome Sizes of Camellia and Related Genera}, volume={54}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI13923-19}, abstractNote={Camellia L., the most speciose member of the diverse tea family Theaceae, has a long and complex horticultural history. Extensive cultivation and hybridization have produced thousands of varieties of Camellia, including commercially important crops such as cultivated tea, oilseed, and iconic flowering shrubs. Cytogenetics of Camellia and related genera is complicated; chromosome number and ploidy can vary widely between species, and interspecific and interploid hybridization occurs. However, specific information regarding cytogenetics of many species, cultivars, and modern hybrids is lacking. The objectives of this study were to compile a consolidated literature review of the cytogenetics of Camellia and related genera and to determine chromosome numbers, ploidy, and genome sizes of specific accessions of selected species, cultivars, and interspecific and interploid hybrids. A review of the existing literature regarding Theaceae cytogenetics is presented as a consolidated reference comprising 362 taxa. Genome sizes were determined with flow cytometry using propidium iodide as a fluorochrome and Pisum sativum ‘Ctirad' and Magnolia virginiana ‘Jim Wilson’ as internal standards. Chromosome numbers of selected taxa were determined using traditional cytology and were used to calibrate genome sizes with ploidy level. Our results confirmed a base chromosome number of x = 15 for Theeae including Camellia, x = 17 for Stewartiae, and x = 18 for Gordoniae. Surveyed camellias ranged from 2n = 2x = 30 to 2n = 8x = 120, including diploids, triploids, tetraploids, pentaploids, hexaploids, and octoploids. Previously uncharacterized taxa such as Camellia azalea, C. amplexicaulis, C. chrysanthoides, C. cordifolia, C. cucphuongensis, C. flava, C. nanyongensis, and C. trichoclada were found to be diploid. Ploidy was also newly determined for Schima argentea, S. khasiana, S. remotiserrata, and S. sinensis (all diploids). Both diploid and triploid Stewartia ovata were found, and a ploidy series was discovered for Polyspora that ranged from diploid to octoploid. Ploidy determinations were used to confirm or challenge the validity of putative interploid hybrids. Monoploid genome sizes varied among subfamily and genera, with 1Cx values ranging from 0.80 pg for Franklinia to a mean of 3.13 pg for Camellia, demonstrating differential rates of genome expansion independent of ploidy. Within Camellia, monoploid genome sizes varied among subgenera, sections, and some species (range, 2.70–3.55 pg). This study provides a consolidated and expanded knowledgebase of ploidy, genome sizes, hybridity, and reproductive pathways for specific accessions of Camellia and related genera that will enhance opportunities and strategies for future breeding and improvement within Theaceae.}, number={7}, journal={HORTSCIENCE}, author={Hembree, William G. and Ranney, Thomas G. and Jackson, Brian E. and Weathington, Mark}, year={2019}, month={Jul}, pages={1124–1142} }
 @article{bartley_jackson_fonteno_2019, title={Effect of particle length to width ratio on sieving accuracy and precision}, volume={355}, ISSN={["1873-328X"]}, DOI={10.1016/j.powtec.2019.07.016}, abstractNote={The physical, hydrological, and physico-chemical properties of horticultural substrates are influenced by particle shape and size. Sieve analysis is the predominate method utilized to characterize the particle size distribution of horticultural substrates. However, the effect of particle length on sieve analysis results have only been speculated. Laser cut particles with eight different length to width (L:W) ratios were sorted by sieves for agitation times ranging from 1 min to 5 min. To quantify the effect of L:W ratio and agitation time, the means (mid-point) and standard deviations of particle distributions were compared. Particles with a 1:1 L:W ratio were the most accurately sorted particles, containing midpoints most similar to true sieve size. As particle length increased, distribution midpoints and standard deviation increased. Elongated particles, 2:1 L:W ratio and greater, may cause the particle size distribution to skew positively. Increasing agitation time influences the probability of a particle and open sieve aperture converging in an orientation which allows it passage and can improve sieve accuracy and precision. By improving the consistency of sieving protocols, the accuracy of sieve analysis could potentially be improved. However, alternative instruments should be evaluated to improve the characterization of horticultural substrates. If, in the future, the characteristics of elongated or complex-shaped particles are desired, it may prove more beneficial to refine engineering practices than rely on sieving to precisely sort and isolate them.}, journal={POWDER TECHNOLOGY}, author={Bartley, Paul C., III and Jackson, Brian E. and Fonteno, William C.}, year={2019}, month={Oct}, pages={349–354} }
 @article{miller_pinnix_bartley_mccauley_jackson_2019, title={Evaluation of Turfgrass Clippings from Mulching Versus Side Discharge Mower Operation}, volume={5}, ISSN={["2374-3832"]}, DOI={10.2134/cftm2019.06.0050}, abstractNote={Mower design and operation have been based on reducing clipping size to enhance filtering into the turfgrass canopy away from the surface. Reduced clippings on the surface can increase surface uniformity, a primary goal for lawn mower use. This study was conducted to determine the effectiveness of mulching mower units to reduce clipping particle size compared with traditional side-discharge mower units. Three commercially available mowers of different horsepower/ size were tested in mulching and side-discharge modes of operation to evaluate clipping parameters from tall fescue and zoysiagrass maintained under typical home-lawn conditions. Turfgrass species and mower size had a greater impact on clipping length and specific projected area than mode of operation. Tall fescue clippings were 28% longer than zoysiagrass and had a 34% greater specific projected area. A medium or large mower produced clippings 28 to 31% shorter than the small mower and decreased the specific projected area by 19 to 32%. Mulching operation did not decrease clipping size as hypothesized. Instead, mulching resulted in average increases of 9 and 0.2% in clipping length and specific projected area, respectively. A side discharge mode of operation may result in fewer clippings on the surface, increasing surface uniformity compared to a mulching mode of operation. I t has been reported that recycling lawn clippings promotes retention of plant nutrients and enhances turfgrass quality (Heckman et al., 2000; Kopp and Guillard, 2002; Bigelow et al., 2005). Little information has been found in the literature as it relates to turfgrass particle size from mowing and decomposition rates. Studies by Angers and Recous (1997) reported the decomposition of rye (Secale cereal L.) green residues and wheat (Triticum aestivum L.) straw was influenced by particle size. It seems reasonable to postulate from previous work that smaller turfgrass clippings are more likely to filter down through the turfgrass canopy to the soil surface, enhancing the onset of decomposition and providing an environmental benefit. From a consumer’s perspective, fewer clippings visible on the turfgrass surface can result in a more uniform, attractive turfgrass canopy. Rotary lawn mowers are equipped with decks that house one to three horizontal rotating blades that cut turfgrasses. The decks of these mowers are designed to lift, cut, and discharge leaf tissue through side or rear orifices. Many mowers offer a mulching Crop Forage Turfgrass Manage. 5:190050. doi:10.2134/cftm2019.06.0050 © 2019 The author(s). Re-use requires permission from the publisher. Published October 17, 2019}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Miller, Grady L. and Pinnix, Garland D. and Bartley, Paul C. and McCauley, Raymond K. and Jackson, Brian E.}, year={2019}, month={Oct} }
 @article{stewart_marble_jackson_pearson_wilson_lauer_2019, title={Influence of Pine Bark Substrate Age on Performance and Leaching of Nursery Preemergence Herbicides}, volume={54}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI13748-18}, abstractNote={The objective of these experiments was to determine if preemergence herbicides perform similarly across pine bark that was aged for varying lengths of time including 0, 4, 8, and 12 months after bark removal from harvested trees. Three preemergence herbicides were evaluated for three separate weed species, including 1) Cardamine flexuosa With. (bittercress) with isoxaben, 2) Digitaria sanguinalis (L.) Scop. (large crabgrass) with prodiamine, and 3) Oxalis stricta L. (woodsorrel) with dimethenamid-P. Leaching of herbicides through substrates was evaluated for prodiamine. Weed growth in the various substrates was variable, but few differences were detected in weed growth among the pine bark substrates evaluated. For isoxaben and prodiamine, weed control was similar among the pine bark substrates in most cases when label rates were applied. Although some differences were detected in prodiamine performance across different pine bark ages, a high level of control was achieved in all cases at rates well below manufacturer recommendations. Prodiamine leaching was minimal in all substrates. It would be recommended that growers test substrates for physical properties before use so that irrigation and other production inputs could be modified if needed. In most cases, growers should expect similar performance of preemergence herbicides regardless of pine bark substrate age.}, number={5}, journal={HORTSCIENCE}, author={Stewart, Cody J. and Marble, S. Christopher and Jackson, Brian and Pearson, Brian J. and Wilson, P. Christopher and Lauer, Dwight K.}, year={2019}, month={May}, pages={896–902} }
 @article{altland_owen_jackson_fields_2018, title={Physical and Hydraulic Properties of Commercial Pine-bark Substrate Products Used in Production of Containerized Crops}, volume={53}, ISSN={["2327-9834"]}, DOI={10.21273/HORTSCI13497-18}, abstractNote={Pine bark is the primary constituent of nursery container media (i.e., soilless substrate) in the eastern United States. Pine bark physical and hydraulic properties vary depending on the supplier due to source (e.g., lumber mill type) or methods of additional processing or aging. Pine bark can be processed via hammer milling or grinding before or after being aged from ≤1 month (fresh) to ≥6 month (aged). Additionally, bark is commonly amended with sand to alter physical properties and increase bulk density (Db). Information is limited on physical or hydraulic differences of bark between varying sources or the effect of sand amendments. Pine bark physical and hydraulic properties from six commercial sources were compared as a function of age and amendment with sand. Aging bark, alone, had little effect on total porosity (TP), which remained at ≈80.5% (by volume). However, aging pine bark from ≤1 to ≥6 months shifted particle size from the coarse (>2 mm) to fine fraction (<0.5 mm), which increased container capacity (CC) 21.4% and decreased air space (AS) by 17.2% (by volume) regardless of source. The addition of sand to the substrate had a similar effect on particle size distribution to that of aging, increasing CC and Db while decreasing AS. Total porosity decreased with the addition of sand. The magnitude of change in TP, AS, CC, and Db from a nonamended pine bark substrate was greater with fine vs. coarse sand and varied by bark source. When comparing hydrological properties across three pine bark sources, readily available water content was unaffected; however, moisture characteristic curves (MCC) differed due to particle size distribution affecting the residual water content and subsequent shift from gravitational to either capillary or hygroscopic water. Similarly, hydraulic conductivity (i.e., ability to transfer water within the container) decreased with increasing particle size.}, number={12}, journal={HORTSCIENCE}, author={Altland, James E. and Owen, James S., Jr. and Jackson, Brian E. and Fields, Jeb S.}, year={2018}, month={Dec}, pages={1883–1890} }
 @article{evans_jackson_popp_sadaka_2017, title={Chemical Properties of Biochar Materials Manufactured from Agricultural Products Common to the Southeast United States}, volume={27}, ISSN={["1943-7714"]}, DOI={10.21273/horttech03481-16}, abstractNote={The use of biochar as a soil amendment has fostered much attention in recent years due to its potential of improving the chemical, physical, and biological properties of agricultural soils and/or soilless substrates. The objective of this study was to evaluate the chemical properties of feedstocks, common in the southeast United States, and their resulting biochar products (after being torrefied) and determine if the chemical properties were within suitable ranges for growers to use the biochar products as root substrate components. Poultry litter biochar produced at 400 °C for 2 hours had a higher total phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), sodium (Na), and zinc (Zn) concentration than biochar made using the same process with mixed hard wood species, miscanthus (Miscanthus capensis), cotton (Gossypium hirsutum) gin trash, switchgrass (Panicum virgatum), rice (Oryza sativa) hull, and pine (Pinus sp.) shavings feedstocks. The pH of the biochar products ranged from 4.6 for pine shaving biochar to 9.3 for miscanthus biochar. The electrical conductivity (EC) ranged from 0.1 dS·m−1 for mixed hardwood biochar to 30.3 dS·m−1 for poultry litter biochar. The cation exchange capacity (CEC) of the biochar products ranged from a low of 0.09 meq/g for mixed hardwood biochar to a high of 19.0 meq/g for poultry litter biochar. The water-extractable nitrate, P, K, Ca, Mg, sulfate, boron, Cl, Cu, Fe, Mo, Na, and Zn were higher in poultry litter biochar than in all of the other types of biochar. The high EC and mineral element concentration of the poultry litter biochar would prevent its use in root substrates except in very small amounts. In addition, the high degree of variability in chemical properties among all of the biochar products would require users to know the specific properties of any biochar product they used in a soil or soilless substrate. Modifications to traditional limestone additions and fertility programs may also need to be tested and monitored to compensate for the biochar pH and mineral nutrient availability. Users should be aware that biochar products made from different feedstocks can have very different chemical properties even if the same process was used to manufacture them.}, number={1}, journal={HORTTECHNOLOGY}, author={Evans, Michael R. and Jackson, Brian E. and Popp, Michael and Sadaka, Sammy}, year={2017}, month={Feb}, pages={16–23} }
 @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{blok_jackson_guo_visser_marcelis_2017, title={Maximum Plant Uptakes for Water, Nutrients, and Oxygen Are Not Always Met by Irrigation Rate and Distribution in Water-based Cultivation Systems}, volume={8}, ISSN={["1664-462X"]}, DOI={10.3389/fpls.2017.00562}, abstractNote={Growing on rooting media other than soils in situ -i.e., substrate-based growing- allows for higher yields than soil-based growing as transport rates of water, nutrients, and oxygen in substrate surpass those in soil. Possibly water-based growing allows for even higher yields as transport rates of water and nutrients in water surpass those in substrate, even though the transport of oxygen may be more complex. Transport rates can only limit growth when they are below a rate corresponding to maximum plant uptake. Our first objective was to compare Chrysanthemum growth performance for three water-based growing systems with different irrigation. We compared; multi-point irrigation into a pond (DeepFlow); one-point irrigation resulting in a thin film of running water (NutrientFlow) and multi-point irrigation as droplets through air (Aeroponic). Second objective was to compare press pots as propagation medium with nutrient solution as propagation medium. The comparison included DeepFlow water-rooted cuttings with either the stem 1 cm into the nutrient solution or with the stem 1 cm above the nutrient solution. Measurements included fresh weight, dry weight, length, water supply, nutrient supply, and oxygen levels. To account for differences in radiation sum received, crop performance was evaluated with Radiation Use Efficiency (RUE) expressed as dry weight over sum of Photosynthetically Active Radiation. The reference, DeepFlow with substrate-based propagation, showed the highest RUE, even while the oxygen supply provided by irrigation was potentially growth limiting. DeepFlow with water-based propagation showed 15–17% lower RUEs than the reference. NutrientFlow showed 8% lower RUE than the reference, in combination with potentially limiting irrigation supply of nutrients and oxygen. Aeroponic showed RUE levels similar to the reference and Aeroponic had non-limiting irrigation supply of water, nutrients, and oxygen. Water-based propagation affected the subsequent cultivation in the DeepFlow negatively compared to substrate-based propagation. Water-based propagation resulted in frequent transient discolorations after transplanting in all cultivation systems, indicating a factor, other than irrigation supply of water, nutrients, and oxygen, influencing plant uptake. Plant uptake rates for water, nutrients, and oxygen are offered as a more fundamental way to compare and improve growing systems.}, journal={FRONTIERS IN PLANT SCIENCE}, author={Blok, Chris and Jackson, Brian E. and Guo, Xianfeng and Visser, Pieter H. B. and Marcelis, Leo F. M.}, year={2017}, month={Apr} }
 @article{judd_jackson_fonteno_domec_2016, title={Measuring root hydraulic parameters of container-grown herbaceous and woody plants using the hydraulic conductance flow meter}, volume={51}, number={2}, journal={HortScience}, author={Judd, L. A. and Jackson, B. E. and Fonteno, W. C. and Domec, J. C.}, year={2016}, pages={192–196} }
 @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} }
 @article{judd_jackson_fonteno_evans_boyette_2015, title={Changes in Root Growth and Physical Properties in Substrates Containing Charred or Uncharred Wood Aggregates (c)}, volume={1085}, ISSN={["2406-6168"]}, DOI={10.17660/actahortic.2015.1085.86}, journal={PROCEEDINGS OF THE 2014 ANNUAL MEETING OF THE INTERNATIONAL PLANT PROPAGATORS SOCIETY}, author={Judd, Lesley A. and Jackson, Brian E. and Fonteno, William C. and Evans, Michael R. and Boyette, Michael D.}, year={2015}, pages={421–425} }
 @article{judd_jackson_fonteno_2015, title={Rhizometer: An apparatus to observe and measure root growth and its effect on container substrate physical properties over time}, volume={50}, number={2}, journal={HortScience}, author={Judd, L. A. and Jackson, B. E. and Fonteno, W. C.}, year={2015}, pages={288–294} }
 @inproceedings{yap_jackson_fonteno_2015, title={Water retention of processed pine wood and pine bark and their particle size fractions ?}, volume={1085}, DOI={10.17660/actahortic.2015.1085.95}, booktitle={Proceedings of the 2014 annual meeting of the international plant propagators society}, author={Yap, T. C. and Jackson, B. E. and Fonteno, W. C.}, year={2015}, pages={467–471} }
 @inproceedings{kraus_pledger_riley_fonteno_jackson_bilderback_arboretum_2014, title={Defining rain garden filter bed substrates based on saturated hydraulic conductivity}, volume={1034}, booktitle={International symposium on growing media and soilless cultivation}, author={Kraus, H. and Pledger, R. and Riley, E. and Fonteno, W. C. and Jackson, B. E. and Bilderback, T. and Arboretum, J. C. R.}, year={2014}, pages={57–64} }
 @article{fields_fonteno_jackson_2014, title={Hydration efficiency of traditional and alternative greenhouse substrate components}, volume={49}, number={3}, journal={HortScience}, author={Fields, J. S. and Fonteno, W. C. and Jackson, B. E.}, year={2014}, pages={336–342} }
 @article{fields_fonteno_jackson_heitman_owen_2014, title={Hydrophysical properties, moisture retention, and drainage profiles of wood and traditional components for greenhouse substrates}, volume={49}, number={6}, journal={HortScience}, author={Fields, J. S. and Fonteno, W. C. and Jackson, B. E. and Heitman, J. L. and Owen, J. S.}, year={2014}, pages={827–832} }
 @article{judd_jackson_yap_fonteno_2014, title={Mini-horhizotron: An apparatus for observing and measuring root growth of container-grown plant material in situ}, volume={49}, number={11}, journal={HortScience}, author={Judd, L. A. and Jackson, B. E. and Yap, T. C. and Fonteno, W. C.}, year={2014}, pages={1424–1431} }
 @inproceedings{fields_fonteno_jackson_2014, title={Plant available and unavailable water in greenhouse substrates: Assessment and considerations}, volume={1034}, DOI={10.17660/actahortic.2014.1034.42}, abstractNote={Accurate assessment of available water in substrates usually includes a measurement of water unavailable to plants. Plant roots have an ability to pull suctions up to 1.0 to 2.0 MPa, depending on species, with the classic value for unavailability measured at 1.5 MPa. Five samples each of peat moss, pine bark and perlite and a clay soil were placed in a 1.5 MPa porous plate system for 48 hours. The samples were then removed and run in a dewpoint potentiometer then dried for 24 hours at 105°C. The mineral soil potentials averaged 1.39 MPa, but the others were much smaller: peat = 0.38, bark = 0.21 and perlite = 0.28 MPa. Peat and bark were re-tested at 0.3 MPa on the porous plate system then placed in the potentiometer. The peat water potential was 0.33 MPa while the bark was 0.34 MPa, showing good agreement with the porous plate pressures. The samples of highly porous materials of peat, bark and perlite possibly seemed to lose hydraulic continuity between the samples and porous plate above 0.3 MPa of pressure which stopped the flow of water from the samples. This resulted in artificially high values. In a second study, substrate samples (3 peat: 1 perlite: 1 vermiculite, v/v/v) were taken from mature marigold plants in three stages of wilt: Stage 1: light wilt (initial leaf flagging), Stage 2: moderate wilt (leaves wilted to ~ 45°of vertical) and Stage 3: heavy wilt (leaves wilted and curled to main stem). Water potentials were measured at each stage using the potentiometer. After substrate sampling, each plant was re-watered and level of recovery was noted. Plants at Stage 1 wilt had soil potentials of ~ 0.6 MPa. Stage 2 wilt was at ~ 1.55 MPa and Stage 3 wilt was ~ 2.2 MPa. All plants visually recovered from wilt at all stages. The potentiometer may be useful in determining actual soil water potentials under dry conditions, not normally measurable using the traditional porous plate system. Unavailable water content for horticultural substrates may be overly high using the porous plate system as confirmed with the dew point potentiometer. Measuring water potentials during plant wilt may help to refine the nature of permanent wilt and more precisely determine water is truly unavailable to plants. INTRODUCTION The term available water capacity, first defined by Veihmeyer and Hendrickson (1927), describes water held in a soil between field capacity (or container capacity in horticultural substrates) and the permanent wilting point (PWP). Permanent wilt describes the condition where a plant has reached a low enough water potential that there can be no recovery (Taiz and Zeiger, 1996). Richards and Wadleigh (1952) found that the PWP for most agricultural crops is between -1.0 and -2.0 MPa, with the convention of -1.5 MPa to be PWP. Plants do not generally reach permanent wilt at the instant they reach this potential, but instead gradually reduce transpiration until available water is lost. Denmead and Shaw (1962) showed that many plants start to reduce transpiration rate at as low as 0.2 MPa. In order to determine available water content, container capacity and unavailable water must be measured. To measure UW, Bouyoucos (1929) described an apparatus which produces a suction equal to -1.5 MPa which draws upon a soil sample. This idea was refined by Richards and Fireman (1943) who applied 1.5 MPa of pressure, and Proc. IS on Growing Media & Soilless Cultivation Eds.: C. Blok et al. Acta Hort. 1034, ISHS 2014 342 employed the use of porous plates which soil samples are placed upon to allow water to be moved out of the samples until equilibrium is reached with the 1.5 MPa pressure that has been applied. A modified version of Richards and Fireman’s pressure plates is currently the most common method of measuring UW, along with the plant-based method using sunflower (Cassel and Nielsen, 1986). The sunflower method was first proposed by Furr and Reeve (1945) and involves growing sunflower seedlings and allowing them to wilt until PWP is reached, and measuring soil water content. The sunflower method can take long periods of time and due to the noninstantaneous wilt of plants, this method can lack in accuracy. However, inaccuracies have been reported with the use of pressure plates at tensions as high as -1.5 MPa (Stevenson, 1982; Fonteno and Bilderback, 1993; Gee et al., 2002). A possible explanation for the inaccuracies with pressure plates is the loss of hydraulic connectivity, or the lack of an unbroken water column throughout the sample. If the water column between the plate and the length of the sample is broken, pressure will be applied to either end of the sample, and thus result in no net flow of water. Recent research by Curtis and Claassen (2008) has shown the effectiveness of using dewpoint potentiometry to measure the water potential of inorganic amendments with higher precision. The objectives of this research were: 1) to determine the potentials reached when -1.5 MPa are applied to organic greenhouse substrate components, and 2) to determine soil water potentials of plants grown in container substrates during the wilting process. MATERIALS AND METHODS This experiment required the use of pressure plate extractors (PPE; Soilmoisture Equipment Corp.; Santa Barbara, CA) and a WP4C Dewpoint Potentiometer (Decagon; Pullman, WA). Traditional horticultural substrate components including, sphagnum peat moss (Premier Tech, Canada), aged pine bark, and perlite, were tested along with a clay mineral soil classified as Gerogiaville. Five rubber rings were placed on each moistened 1.5 MPa pressure plate, and each ring was filled with one of the materials being tested. In total 20 total samples were tested (4 materials, 5 replications). The samples were saturated for 24 h, and placed in PPEs. Flat circular lead weighs were placed on top of each sample, in order apply a slight downward force to ensure connectivity between the plate and the sample. Nitrogen gas (N2) was then slowly passed into the PPEs until the PPEs were pressurized to 1.5 MPa. The pressure in the PPEs was maintained for 48 h. The samples were then removed, sealed and measured in the WP4C dewpoint potentiometer. The dewpoint potentiometer uses a chilled-mirror dewpoint technique. Relative humidity is measured until equilibrium is attained between the air in the chamber and the sample. Water potentials were determined using repeated measures until successive readings were equal. Testing the samples from the pressure plate allowed the measurement of water potential rendered after pressures of 1.5 MPa. Experiment Two – Plant Wilt Plastic containers of 7.6 cm diameter and 7.6 cm height were filled with a substrate consisting of a mixture of peat: vermiculite: perlite (3:1:1, v/v/v) at a bulk density of 0.13 g/cm3 to ensure uniformity. Marigold (Tagetes erecta L.) seeds were sewn directly into the containers, placed into the greenhouse and irrigated as needed. Fertilization was with 200 ppm N (total) in liquid feed once every 2 to 4 days. Once these plants were mature and flowering the rooting environment (after approximately 8 weeks), each container was saturated, allowed to drain and to begin the wilting process. The plants were observed for wilting until the plant reached one of the three stages of visible wilt (Fig. 1): Stage 1 – initial flagging; Stage 2 – leaves wilted with stems drooping to an angle of 45°; and Stage 3 – all leaves completely wilted. Once at the appropriate wilt stage, plants were photographed and removed from the container. A soil sample approximately 2 cm wide was removed from the top to the bottom of the substrate. Any visible roots were removed and a portion of the sample was placed}, booktitle={International symposium on growing media and soilless cultivation}, author={Fields, J. S. and Fonteno, W. C. and Jackson, B. E.}, year={2014}, pages={341–346} }
 @inproceedings{judd_jackson_fonteno_2014, title={Rhizometrics: A review of three in situ techniques for observation and measurement of plant root systems in containers}, volume={1034}, DOI={10.17660/actahortic.2014.1034.48}, abstractNote={Rhizometrics is a term derived from rhizo- (rhizosphere) and -metrics (series of parameters or measures of quantitative assessment used for measuring, comparisons or tracking performance or production), to describe several methods either developed or examined by North Carolina State University to observe and quantify root growth of plants in containers. Three new techniques have been developed and/or investigated as potential new methods of quantifying root growth; 1) Mini-Horhizotron; 2) Rhizometer; and 3) Hydraulic Conductance Flow Meter (HCFM). First, the mini-Horhizotrons have a clear, three-arm configuration suitable for observing root growth of small container plant material. The clear arms allow for visible access and measurements of plant roots. Potential measurements include root length, quantity of root hairs, and root architecture. Second, the Rhizometer is made from a clear cylinder that is 7.6 cm tall x 7.6 cm inside diameter, which allows for visible observations of root systems and they can be fitted in the North Carolina State University Porometer for in situ measurements of the influence of root growth on physical properties in containers during crop production. Thirdly, the HCFM is an apparatus that measures root and shoot conductance based on pressure and water flow through the roots, in the opposite direction of normal transpiration under quasi-steady-state conditions. Conductance values are directly indicative (and correlated) with root mass. These Rhizometric techniques are novel methods of observing and quantifying root growth and potentially identifying ways of improving root growth productivity and efficiency to maximize crop growth. These techniques have also been used to quantify root growth differences between/among various substrates. A summary of the initial experiments testing the usefulness of these three techniques for quantifying undisturbed root growth have yielded promising results.}, booktitle={International symposium on growing media and soilless cultivation}, author={Judd, L. A. and Jackson, B. E. and Fonteno, W. C.}, year={2014}, pages={389–397} }
 @inproceedings{fonteno_fields_jackson_2013, title={A pragmatic approach to wettability and hydration of horticultural substrates}, volume={1013}, DOI={10.17660/actahortic.2013.1013.15}, abstractNote={Moisture retention has been a key property in substrate analysis for many years. This work explores the relationship between wettability and hydration using a low cost, practical system. Hydration curves and maximum hydration were used to determine three indexes: HE 1 (initial hydration), HE 3 (a watered-in value) and HE 10 (comparing irrigated vs maximum values). Coir, pine bark and sand at 45% moisture and wetting agent reached maximum values with one hydration. However, both coir and peat captured less than half their max in initial hydration when initial moisture was reduced to 30%. Values obtained with this method numerically described common behaviors of substrates, moisture content and wetting agents. INTRODUCTION Many production practices are being reexamined to insure that they better fit with an overall sustainable process. Irrigation efficiency and water conservation is one such area. Part of this effort should be the examination of substrates for their ability to capture and retain the irrigation water delivered to them. The more efficient these mixes, the less water wasted. Hydration of substrates has been studied for wettability (Michel et al., 2001; Urrestarazu et al., 2007; Levesque and Dinel, 1977; Bilderback and Lorscheider, 1997) and capacity (Handreck and Black, 1984; Puustjarvi, 1974; Milks et al., 1989; Wallach et al., 1992). Both areas are vital to hydration, but neither completely describes the effect of an irrigation event on water capture and retention. The purpose of this work is to expand the description of water capture and retention. This process needs to be described in all substrates, so the procedure should be practical, simple and economical for all levels of investigation. The approach was to perform an irrigation event and determine the water content of the substrate. By performing repeated events, one could develop a hydration curve. This would show how quickly a substrate captured the water applied as well as the quantity. By itself, this information is valuable, but the efficiency of water uptake can only be measured against a capacity or maximum value that the substrate could hold. Therefore this work developed a process to determine the rate of uptake and compared it to maximum uptake values. Since water uptake is greatly affected by water content and degree of hydrophobicity, substrate treatments included these parameters. MATERIALS AND METHODS The equipment for the hydration unit consisted of a transparent cylinder, 5 diameter x 15 cm height, with a mesh screen on the bottom; a 100 ml plastic vial (4 cm dia); a 250 ml separatory funnel; and a 250 ml beaker on the bottom (Fig. 1). The vial was fitted with a large O ring and placed in the top the transparent cylinder. The O ring allowed for exact positioning of the vial above the substrate surface to control hydraulic head. The vial had 5 holes in the bottom and acted as a diffuser for the force of the water as it contacted the substrate. Water went from the funnel through the diffuser, into the substrate and out to the beaker. The flow of water was controlled at 2-3 liters per hour with the funnel stopcock. The water dripped evenly from the five holes in the diffuser onto the substrate. If ponding Proc. IS on Growing Media, Composting and Substrate Analysis Eds.: F.X. Martínez et al. Acta Hort. 1013, ISHS 2013 140 occurred, hydraulic head was kept to 1 to 2 cm. A hydration event used 200 ml water through the substrate with the above conditions. Any water effluent going through the substrate was recorded and the moisture retained was calculated by subtraction. Ten hydration events were performed on each substrate with 4 replications per treatment. Materials tested were coir pith (Densu Coir, Canada), peat moss (Premier Tech, Canada), composted pine bark (Pacific Organics, NC), and sand (Builder’s grade, NC). All substrates were tested at three moisture contents, both with and without wetting agent. Wetting agent was AquaGro-L at 187 ml/m3. Samples were moistened to 1.5 mass wetness (MW), then air dried down to 0.82, 0.43, and 0.18 MW, representing moisture contents of 45, 30 and 15% by weight. These levels were too high for sand and it was wetted and dried to 15, 10 and 5% moisture. Cylinders were filled and firmed to 200 ml of sample and packed to specific target densities for each material. All replications within a substrate treatment were packed to within 5% by weight. As substrate heights changed in the process, heights were recorded at three points on each surface and averaged. The diffuser prevented much unevenness of the substrate surfaces. Maximum hydration was measured in a similar fashion as container capacity. After 10 hydrations, the sample cylinder was removed from the hydration unit, weighed and placed into a Buchner funnel with holes as described in the NCSU Porometer Manual (Fonteno, 2010). Water was slowly added from the bottom in a stepwise manner until it reached the top of the substrate surface. After 15 minutes, the water was drained from the sample, allowed to drain for 30 minutes then weighed. Samples were then placed in a forced-air drying oven at 105°C for 24-48 h until dry. Water retention was used to create hydration curves and expressed as a percent age of the total volume. Hydration efficiency was expressed as the percent volume container water compared to the maximum water content it could hold. Efficiency was examined at three points. Initial hydration (HE 1) was the water held after the first hydration event divided by the maximum hydration. HE 3 was the water held after the third hydration event divided by the max. This was considered the “watered-in” level – a level that is reached after hydrating a substrate for production. HE 10 was the water content held after the tenth hydration event divided by the max. This was used to determine if the substrate ever reached the maximum hydration by irrigation. The experiment was a completely randomized design. Statistical mean separation was done with LSD (p 0.05) using SAS (Cary, North Carolina). RESULTS AND DISCUSSION Hydration curves for coir are shown in Figure 2. Water retention is displayed as percent volume of substrate. For comparison, the moisture contents of 15, 30 and 45% by weight are displayed as 2, 4 and 7% by volume at 0 hydrations. The coir without wetting agent hydrated quickly at the first hydration to over 60% by volume and took up little water afterward. At 30% initial moisture, the uptake was much less (20%) and only increased in 8 to 10% increments with each additional hydration. At 15% initial moisture, the coir took up even less water and never reached the levels of the 30 and 45% treatments. Maximum values for 30 and 45% were the same (~70%) while the 15% treatment was significantly less. With wetting agent, the wetting curve response was similar at 45% moisture although slightly higher. However, both the 15 and 30% treatments reached similar maximum levels. Maximum values for all coir treatments were the same, except for the 15% without wetting agent (Table 1). Peat without wetting agent took up much less water than the coir treatments at 45 and 30% (Fig. 3). The 15% treatment of peat was too hydrophobic to take up water consistently and the data is not shown. With wetting agent, peat took up water similarly to coir with wetting agent at 45% moisture. However, the peat at 30 and 15% took up much smaller amounts at each hydration and never reached maximum hydration. Pine bark reached maximum hydrations by the third hydration event in all treatments except the 15% moisture without wetting agent. Sand wet up to maximum levels at}, booktitle={International symposium on growing media, composting and substrate analysis}, author={Fonteno, W. C. and Fields, J. S. and Jackson, B. E.}, year={2013}, pages={139–146} }
 @article{judd_jackson_fonteno_2013, title={Novel Methods for Observing and Quantifying Root Growth of Horticultural Crops (c)}, volume={1014}, ISSN={["0567-7572"]}, DOI={10.17660/actahortic.2013.1014.88}, abstractNote={INTRODUCTION A large portion of the U.S. Green Industry is involved with growing plants in containers, including nursery crops, annual bedding plants and potted herbaceous perennials. With such a large portion of the industry in containers, it is important to understand the factors that influence root growth to attain optimal benefits from container production. Several factors that affect root growth include the physical and chemical properties of substrates. Physical properties include porosity and water holding capacity, percentage of fine particles and bulk density (Mathers et al., 2007). Chemical properties include pH, cation exchange capacity and soluble salts (Mathers et al., 2007). There are several known techniques used to measure these factors that affect root growth, but methods used to measure the whole root system or measure the growth of roots over time are not as widely available. It is also not well understood how roots change and affect the physical properties of substrates in the container over time. The most common root system measurements reported in scientific literature are: (1) subjective root ratings and (2) root dry weight measurements. Root ratings, while being non-destructive, are completely subjective to the person rating the root system and can vary person to person. The second method of root washing is widely accepted as a valid determination of root mass but it is well understood/assumed that a percent of root (particularly fine roots) mass is lost. Oliveira et al. (2000) reported that almost 20-40% of the original root weight is lost during root washing of certain plant species. A non-destructive technique for measuring horizontal root growth (HorhizotronTM) was developed at Auburn University and Virginia Tech that offers a simple, non-destructive technique to measure root growth over time (Wright and Wright, 2004). This HorhizotronTM is constructed out of eight panels of glass attached to an aluminum base to form four wedge-shaped quadrants. The HorhizotronTM was built to fit a plant removed from a 1-3-gal container and placed in the center so the quadrants extend away from the root ball. This technique is most appropriate for assessing/observing root growth from rootballs likely to study post-transplant root response. This technique does not allow for observations and study of small plant root development such as, herbaceous plugs and nursery liners. In order to study root growth of seeds, liners and plugs during production, new techniques need to be developed and evaluated. The objectives of this work were: (1) design and testing of a small scale version of a HorhizotronTM suitable for small plant material and (2) design and testing of the Rhizometer, an in situ technique for determining the influence of plant roots on the physical root environment.}, journal={PROCEEDINGS OF THE INTERNATIONAL PLANT PROPAGATORS' SOCIETY}, author={Judd, Lesley A. and Jackson, Brian E. and Fonteno, William C.}, year={2013}, pages={389–394} }
 @inproceedings{fields_jackson_fonteno_2013, title={Pine bark physical properties influenced by bark source and age (c)}, volume={1014}, DOI={10.17660/actahortic.2013.1014.96}, booktitle={Proceedings of the international plant propagators' society}, author={Fields, J. S. and Jackson, B. E. and Fonteno, W. C.}, year={2013}, pages={433–437} }
 @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} }
 @inproceedings{yap_jackson_2013, title={Root growth of horticultural crops as influenced by pine bark age, wood, and sand amendment (c)}, volume={1014}, DOI={10.17660/actahortic.2013.1014.98}, abstractNote={INTRODUCTION When plants are produced in containers their roots are restricted to a small volume; consequently the demands made on the substrate for water, air, nutrients, and support are more intense that those made by plants grown in a field production situation where unrestricted root growth can occur (Bunt, 1988). Vigorous root systems are essential for growth and development of healthy plants. A healthy, functioning root system increases the surface area available for the uptake of water and mineral elements. It is also important to appreciate the fact that root system development, mass and architecture also is critical in providing support, storage and anchorage needed by plants (Jackson et al., 2005; Waisel et al., 2002; Wraith and Wright, 1998). Often excluded from horticultural research, root growth and root system architecture are important factors influencing plant performance and survival (Wright and Wright, 2004). Understanding root growth and development is important to improving plant quality and production success. The capability to observe and measure roots as they grow into a substrate is very useful in determining root growth preference in various substrates. New root measurement techniques have been designed and introduced in recent years which aid in understanding and qualifying root growth of horticultural crops grown in containers (Wright and Wright, 2004; Silva and Beeson, 2011). Pine bark has been the traditional substrate used for the production of nursery crops grown in containers since the 1970s. Both fresh pine bark and aged pine bark have been utilized by growers and analyzed by researchers to determine the best management practices for growing nursery crops (Cobb and Keever, 1984; Harrelson et al., 2004). It is typical that sand is added as an amendment to pine bark for the purpose of adding weight to the container (helps prevent pots from blowing over). Recently, the use/amendment of pine tree substrates (freshly processed loblolly pine wood; PTS) to pine bark has become a trend for some growers and the focus of several researchers (Jackson et al., 2010; Murphy et al., 2010). The effect that these substrate amendments and pine bark age have on root growth in containers is not well known, understood or documented.}, booktitle={Proceedings of the international plant propagators' society}, author={Yap, T. C. and Jackson, B. E.}, year={2013}, pages={443–446} }
 @inproceedings{bilderback_riley_jackson_kraus_fonteno_owen_altland_fain_2013, title={Strategies for developing sustainable substrates in nursery crop production}, volume={1013}, DOI={10.17660/actahortic.2013.1013.2}, abstractNote={A comprehensive literature search of industrial and agricultural by-products to replace or extend existing soilless substrate components would produce a seemingly endless list of materials from “garbage” to a plethora of manure-based composts that have been tested both in the laboratory and in crop response studies throughout the world. Many of these alternatives have shown promise, but limiting factors for integration and use of the alternatives substrate components continue to include: regional or national availability; transport costs; handling costs; lack of a uniform and consistent product; guidelines for preparation and use of materials or impact on current crop production practices. If a product can overcome the above limitations, then researchers are tasked with documenting substrate physical or chemical characteristics. The objective in all studies is to maintain or increase growth of nursery crops and to extend the longevity and acceptable physical properties for long-term woody ornamental crops. Proof of results is determined using laboratory analyses and crop growth studies. Physiochemical properties are monitored over days, weeks, and months to ensure stability. Particle size distribution and varying ratios of substrate components are manipulated to achieve optimal air filled porosity and available water content. Soilless substrates are amended with lime, sulfur and nutrients or blended with other substrate components to provide optimal chemical characteristics. Additionally, substrates are evaluated under industry conditions to determine impact on water, nutrient and pest management to better understand obstacles to commercial adoption.}, booktitle={International symposium on growing media, composting and substrate analysis}, author={Bilderback, T. E. and Riley, E. D. and Jackson, B. E. and Kraus, Helen and Fonteno, W. C. and Owen, J. S. and Altland, J. and Fain, G. B.}, year={2013}, pages={43–56} }
 @article{jackson_wright_barnes_2010, title={Methods of Constructing a Pine Tree Substrate from Various Wood Particle Sizes, Organic Amendments, and Sand for Desired Physical Properties and Plant Growth}, volume={45}, ISSN={["2327-9834"]}, DOI={10.21273/hortsci.45.1.103}, abstractNote={The use of freshly harvested and processed pine trees as a container substrate for greenhouse and nursery crop production is a relatively new concept, and fundamental knowledge of the construction of a pine tree substrate (PTS) for optimal physical properties is insufficient. Therefore, this research was conducted to determine the influence of mixing PTSs produced with different wood particle sizes and adding other amendments to PTS on substrate physical properties and plant growth compared with traditional substrates. Coarse pine wood chips produced from 15-year-old loblolly pine trees (Pinus taeda L.) were ground in a hammermill fitted with either a 4.76-mm screen or with no screen (PTS-NS) allowing a fine and a coarse particle PTS to be produced. Increasing proportions of the finer (4.76-mm) PTS to the coarser PTS (PTS-NS) resulted in increased container capacity (CC) and shoot growth of ‘Inca Gold’ marigold (Tagetes erecta L.). In another study, PTSs were manufactured in a hammermill fitted with different screen sizes: 4.76, 6.35, 9.54, or 15.8 mm as well as PTS-NS. After being hammermilled, each of the five PTSs was then amended (by mixing) with 10% sand (PTS-S), 25% peatmoss (PTS-PM), or left unamended. Pine tree substrates were also produced by adding 25% aged pine bark (PB) to pine wood chips before being ground in a hammermill with each of the five screen sizes mentioned (PTS-HPB). These five substrates were used unamended as well as amended with 10% sand after grinding (PTS-HPBS). Control treatments included peat-lite (PL) and 100% aged PB for a total of 27 substrates evaluated in this study. Container capacity and marigold growth increased as screen size decreased and with the additions of peatmoss (PTS-PM) or hammering with PB (PTS-HPB) to PTS. Container capacity for all substrates amended with peatmoss or PB was within the recommended range of 45% to 65% for container substrates, but only with the more finely ground PTS-4.76-mm resulted in marigold growth comparable to PL and PB. However, when the PTS-NS was amended by mixing in 25% peat or hammering with 25% PB, growth of marigold was equal to plants grown in PL or PB. In a third study, hammering PTS-NS with 25% PB followed by the addition of 10% sand increased dry weight of both azalea (Rhododendron ×hybrida ‘Girard Pleasant White’) and spirea (Spiraea nipponica Maxim. ‘Snowmound’) resulting in growth equal to plants grown in 100% PB. This work shows that amending coarsely ground PTS with finer particle PTS or with other materials (peatmoss, aged PB, or sand) can result in a substrate with comparable physical properties such as CC and plant growth compared with 100% PL or PB.}, number={1}, journal={HORTSCIENCE}, author={Jackson, Brian E. and Wright, Robert D. and Barnes, Michael C.}, year={2010}, month={Jan}, pages={103–112} }
 @article{jackson_wright_gruda_2009, title={Container Medium pH in a Pine Tree Substrate Amended with Peatmoss and Dolomitic Limestone Affects Plant Growth}, volume={44}, ISSN={["2327-9834"]}, DOI={10.21273/hortsci.44.7.1983}, abstractNote={This work was conducted to evaluate the effect of limestone additions to pine tree substrate (PTS) and PTS amended with peatmoss on pH and plant growth. ‘Inca Gold’ marigold (Tagetes erecta L.) and ‘Rocky Mountain White’ geranium (Pelargonium ×hortorum L.H. Bailey) were grown in three PTSs—100% PTS, PTS plus 25% peatmoss (v/v), and PTS plus 50% peatmoss (v/v)—made from freshly harvested loblolly pine trees (Pinus taeda L.) chipped and hammermilled through a 4.76-mm screen and a peatmoss/perlite (4:1 v/v; PL) control. Each substrate was amended with various rates of dolomitic limestone and used to grow marigolds in 10-cm square (l-L) plastic containers and geraniums in round 15-cm (1.25-L) plastic containers in a glasshouse. Regardless of limestone rate, pH was highest in 100% PTS and decreased with peat additions with PL having the lowest pH. As percent peat increased from 25% to 50%, more limestone was required to adjust pH to a particular level showing that PTS is more weakly buffered against pH change than peatmoss. Adding limestone did not increase the growth of marigold in 100% PTS, but additions of limestone did increase growth of marigold when grown in PTS containing peatmoss or in PL. Geranium growth was higher in PTS containing peatmoss (25% or 50%) and PL than in 100% PTS at all limestone rates. This research demonstrates that PTS produced from freshly harvested pine trees has an inherently higher pH than PL, and the additions of peatmoss to PTS require pH adjustment of the substrate for optimal plant growth.}, number={7}, journal={HORTSCIENCE}, author={Jackson, Brian E. and Wright, Robert D. and Gruda, Nazim}, year={2009}, month={Dec}, pages={1983–1987} }