@article{tilley_jordan_vann_gatiboni_heiniger_stevens_ambrose_2023, title={Influence of planting pattern on corn response to sub-surface drip irrigation}, volume={9}, ISSN={["2374-3832"]}, DOI={10.1002/cft2.20247}, abstractNote={NoneThis article is protected by copyright. All rights reserved}, number={2}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Tilley, M. Scott and Jordan, David L. and Vann, Rachel A. and Gatiboni, Luke and Heiniger, Ronnie W. and Stevens, Brian and Ambrose, Derek}, year={2023}, month={Dec} }
 @article{molo_white_cornish_gell_baars_singh_carbone_isakeit_wise_woloshuk_et al._2022, title={Asymmetrical lineage introgression and recombination in populations of Aspergillus flavus: Implications for biological control}, volume={17}, ISSN={["1932-6203"]}, url={https://doi.org/10.1371/journal.pone.0276556}, DOI={10.1371/journal.pone.0276556}, abstractNote={Aspergillus flavus is an agriculturally important fungus that causes ear rot of maize and produces aflatoxins, of which B 1 is the most carcinogenic naturally-produced compound. In the US, the management of aflatoxins includes the deployment of biological control agents that comprise two nonaflatoxigenic A . flavus strains, either Afla-Guard (member of lineage IB) or AF36 (lineage IC). We used genotyping-by-sequencing to examine the influence of both biocontrol agents on native populations of A . flavus in cornfields in Texas, North Carolina, Arkansas, and Indiana. This study examined up to 27,529 single-nucleotide polymorphisms (SNPs) in a total of 815 A . flavus isolates, and 353 genome-wide haplotypes sampled before biocontrol application, three months after biocontrol application, and up to three years after initial application. Here, we report that the two distinct A . flavus evolutionary lineages IB and IC differ significantly in their frequency distributions across states. We provide evidence of increased unidirectional gene flow from lineage IB into IC, inferred to be due to the applied Afla-Guard biocontrol strain. Genetic exchange and recombination of biocontrol strains with native strains was detected in as little as three months after biocontrol application and up to one and three years later. There was limited inter-lineage migration in the untreated fields. These findings suggest that biocontrol products that include strains from lineage IB offer the greatest potential for sustained reductions in aflatoxin levels over several years. This knowledge has important implications for developing new biocontrol strategies.}, number={10}, journal={PLOS ONE}, author={Molo, Megan S. and White, James B. and Cornish, Vicki and Gell, Richard M. and Baars, Oliver and Singh, Rakhi and Carbone, Mary Anna and Isakeit, Thomas and Wise, Kiersten A. and Woloshuk, Charles P. and et al.}, editor={Nierman, William C.Editor}, year={2022}, month={Oct} }
 @article{tilley_jordan_heiniger_vann_crozier_gatiboni_2021, title={A survey of twin-row cropping systems in North Carolina}, volume={7}, ISSN={["2374-3832"]}, DOI={10.1002/cft2.20099}, abstractNote={Abstract Twin‐row (TR) cropping systems have maintained a presence in North Carolina (NC) for more than 30 years. Introduced as an alternative to the single‐row (SR) configuration, it is hypothesized individual plants arranged 7‐ to 9‐inches apart see a decrease in plant‐to‐plant competition. However, the success of TR remains elusive. Only a handful of farmers across NC have been able to increase yield through the implementation of TR. As higher yields are achieved in research using SR, the use of TR is becoming less attractive to growers looking to modernize. In order to understand future trends, two surveys were administered across the state of NC with the following objectives: (a) identify standard production practices used such as row spacing, TR spacing, starter fertilizer placement, and layby application methods, (b) evaluate grower testimonies concerning observed plant stress under diverse environmental conditions, and (c) identify the successes and limitations observed with TR production. Of the 461 farmers surveyed in the general survey, 42% stated they are planting on narrow (30 inch or less) SR with 58% still planting on 36‐inch or greater row spacing. Within the 58%, 148 farmers stated they are considering a transition from wide (>30 inches) to narrow row systems. One hundred and twenty farmers said they would remain on wide SR. In time, 74% of growers will potentially be planting on narrow rows. Twenty‐eight TR farmers (6%) were identified. Two of the 28 twin‐row growers stated they would be reverting back to single‐row production.}, number={1}, journal={CROP FORAGE & TURFGRASS MANAGEMENT}, author={Tilley, M. Scott and Jordan, David L. and Heiniger, Ronnie W. and Vann, Rachel and Crozier, Carl R. and Gatiboni, Luke}, year={2021} }
 @article{mueller_wise_sisson_allen_bergstrom_bissonnette_bradley_byamukama_chilvers_collins_et al._2020, title={Corn Yield Loss Estimates Due to Diseases in the United States and Ontario, Canada, from 2016 to 2019}, volume={21}, ISSN={["1535-1025"]}, DOI={10.1094/PHP-05-20-0038-RS}, abstractNote={Annual reductions in corn (Zea mays L.) yield caused by diseases were estimated by university Extension-affiliated plant pathologists in 26 corn-producing states in the United States and in Ontario, Canada, from 2016 through 2019. Estimated loss from each disease varied greatly by state or province and year. Gray leaf spot (caused by Cercospora zeae-maydis Tehon & E.Y. Daniels) caused the greatest estimated yield loss in parts of the northern United States and Ontario in all years except 2019, and Fusarium stalk rot (caused by Fusarium spp.) also greatly reduced yield. Tar spot (caused by Phyllachora maydis Maubl.), a relatively new disease in the United States, was estimated to cause substantial yield loss in 2018 and 2019 in several northern states. Gray leaf spot and southern rust (caused by Puccinia polysora Underw.) caused the most estimated yield losses in the southern United States. Unfavorable wet and delayed harvest conditions in 2018 resulted in an estimated 2.5 billion bushels (63.5 million metric tons) of grain contaminated with mycotoxins. The estimated mean economic loss due to reduced yield caused by corn diseases in the United States and Ontario from 2016 to 2019 was US$55.90 per acre (US$138.13 per hectare). Results from this survey provide scientists, corn breeders, government agencies, and educators with data to help inform and prioritize research, policy, and educational efforts in corn pathology and disease management.}, number={4}, journal={PLANT HEALTH PROGRESS}, author={Mueller, Daren S. and Wise, Kiersten A. and Sisson, Adam J. and Allen, Tom W. and Bergstrom, Gary C. and Bissonnette, Kaitlyn M. and Bradley, Carl A. and Byamukama, Emmanuel and Chilvers, Martin I and Collins, Alyssa A. and et al.}, year={2020}, pages={238–247} }
 @article{hare_jordan_edmisten_leon_post_vann_dunphy_heiniger_collins_washburn_2020, title={Response of agronomic crops to planting date and double-cropping with wheat}, volume={112}, ISSN={["1435-0645"]}, url={https://doi.org/10.1002/agj2.20164}, DOI={10.1002/agj2.20164}, abstractNote={Abstract Planting date can affect crop yield and is an important management decision for practitioners. Although wheat ( Triticum aestivum L.) and soybean [ Glycine max (L.) Merr.] can be effectively double‐cropped in North Carolina, if commodity prices and projected economic returns are higher for crops other than soybean, growers might consider a nontraditional, double‐crop system. Direct comparisons of major agronomic crops with different planting dates or in a double‐crop system with wheat are limited in North Carolina. Therefore, research was conducted in North Carolina from 2013 through 2017 to determine yield potential of corn ( Zea mays L.), cotton ( Gossypium hirsutum L.), grain sorghum [ Sorghum bicolor (L.) Moench], peanut ( Arachis hypogaea L.), and soybean planted at two dates within the recommended planting window for full‐season production versus planting these crops after wheat harvest. The experimental design was a split plot, with summer crop serving as the whole plot unit and planting date within a crop serving as the subplot unit. Yield of corn, cotton, grain sorghum, peanut, and soybean in full‐season production exceeded that of double‐cropping with wheat in 5, 5, 2, 4, and 5 yr out of 5 yr of the study, respectively. Estimated economic returns were generated using the 10‐yr average (2008–2017) summer crop prices with the 10‐yr average wheat price. When considering all possible combinations of years and crops (n = 25), in only 20% of the possible combinations was the economic return of the double‐cropping system greater than economic return of full‐season crop production when compared with at least one of the planting dates within the traditional planting window.}, number={3}, journal={AGRONOMY JOURNAL}, publisher={Wiley}, author={Hare, Andrew T. and Jordan, David L. and Edmisten, Keith L. and Leon, Ramon G. and Post, Angela R. and Vann, Rachel and Dunphy, E. James and Heiniger, Ronnie and Collins, Guy and Washburn, Derek}, year={2020}, pages={1972–1980} }
 @article{havlin_heiniger_2020, title={Soil Fertility Management for Better Crop Production}, volume={10}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy10091349}, abstractNote={Increasing crop productivity per unit of land area to meet future food and fiber demand increases both soil nutrient removal and the importance of replenishing soil fertility through efficient nutrient management practices. Significant progress in enhancing nutrient-use efficiency in production agriculture requires improved estimates of plant-available nutrients in the root zone, enhanced crop response to applied nutrients, and reduced offsite nutrient transport. This special issue, Soil Fertility Management for Better Crop Production, presents 15 manuscripts that advance our knowledge of interrelated soil, plant, and management factors important to increasing the nutrient availability and crop recovery of applied nutrients.}, number={9}, journal={AGRONOMY-BASEL}, author={Havlin, John and Heiniger, Ron}, year={2020}, month={Sep} }
 @article{lewis_carbone_luis_payne_bowen_hagan_kemerait_heiniger_ojiambo_2019, title={Biocontrol Strains Differentially Shift the Genetic Structure of Indigenous Soil Populations of Aspergillus flavus}, volume={10}, ISSN={1664-302X}, url={http://dx.doi.org/10.3389/fmicb.2019.01738}, DOI={10.3389/fmicb.2019.01738}, abstractNote={Biocontrol using non-aflatoxigenic strains of Aspergillus flavus has the greatest potential to mitigate aflatoxin contamination in agricultural produce. However, factors that influence the efficacy of biocontrol agents in reducing aflatoxin accumulation under field conditions are not well-understood. Shifts in the genetic structure of indigenous soil populations of A. flavus following application of biocontrol products Afla-Guard and AF36 were investigated to determine how these changes can influence the efficacy of biocontrol strains in reducing aflatoxin contamination. Soil samples were collected from maize fields in Alabama, Georgia, and North Carolina in 2012 and 2013 to determine changes in the population genetic structure of A. flavus in the soil following application of the biocontrol strains. A. flavus L was the most dominant species of Aspergillus section Flavi with a frequency ranging from 61 to 100%, followed by Aspergillus parasiticus that had a frequency of <35%. The frequency of A. flavus L increased, while that of A. parasiticus decreased after application of biocontrol strains. A total of 112 multilocus haplotypes (MLHs) were inferred from 1,282 isolates of A. flavus L using multilocus sequence typing of the trpC, mfs, and AF17 loci. A. flavus individuals belonging to the Afla-Guard MLH in the IB lineage were the most dominant before and after application of biocontrol strains, while individuals of the AF36 MLH in the IC lineage were either recovered in very low frequencies or not recovered at harvest. There were no significant (P > 0.05) differences in the frequency of individuals with MAT1-1 and MAT1-2 for clone-corrected MLH data, an indication of a recombining population resulting from sexual reproduction. Population mean mutation rates were not different across temporal and spatial scales indicating that mutation alone is not a driving force in observed multilocus sequence diversity. Clustering based on principal component analysis identified two distinct evolutionary lineages (IB and IC) across all three states. Additionally, patristic distance analysis revealed phylogenetic incongruency among single locus phylogenies which suggests ongoing genetic exchange and recombination. Levels of aflatoxin accumulation were very low except in North Carolina in 2012, where aflatoxin levels were significantly (P < 0.05) lower in grain from treated compared to untreated plots. Phylogenetic analysis showed that Afla-Guard was more effective than AF36 in shifting the indigenous soil populations of A. flavus toward the non-toxigenic or low aflatoxin producing IB lineage. These results suggest that Afla-Guard, which matches the genetic and ecological structure of indigenous soil populations of A. flavus in Alabama, Georgia, and North Carolina, is likely to be more effective in reducing aflatoxin accumulation and will also persist longer in the soil than AF36 in the southeastern United States.}, journal={Frontiers in Microbiology}, publisher={Frontiers Media SA}, author={Lewis, Mary H. and Carbone, Ignazio and Luis, Jane M. and Payne, Gary A. and Bowen, Kira L. and Hagan, Austin K. and Kemerait, Robert and Heiniger, Ron and Ojiambo, Peter S.}, year={2019}, month={Jul} }
 @article{babu_reisig_walgenbach_heiniger_everman_2019, title={Influence of Weed Manipulation in Field Borders on Brown Stink Bug (Hemiptera: Pentatomidae) Densities and Damage in Field Corn}, volume={48}, ISSN={0046-225X 1938-2936}, url={http://dx.doi.org/10.1093/ee/nvz016}, DOI={10.1093/ee/nvz016}, abstractNote={Abstract Brown stink bug, Euschistus servus (Say), is a damaging pest of corn, Zea mays L. (Cyperales: Poaceae), in the southeastern United States. In North Carolina, during the spring, winter-planted wheat, Triticum aestivum L. (Cyperales: Poaceae), serves as the earliest available crop host, and E. servus seems to prefer this crop over seedling corn. In the absence of wheat in the agroecosystem, weeds serve as a bridge host for a portion of overwintered E. servus populations until they move to corn and other subsequent crops. Our objective was to reduce densities of E. servus in corn by manipulating the weedy field borders with mowing and applications of dicamba herbicide. During the study, multiple species of stink bugs (n =16) were found associated with weed plots. However, E. servus was the predominant (>94%) stink bug species in the corn. In this farmscape, density of E. servus adults in the unmanaged weed plots began declining around the second week of May, followed by an increase in density in adjacent corn plots. This movement coincided with the seedling growth of corn. In 2016, applications of dicamba in the weedy field border resulted in a lower density of E. servus in herbicide-treated weed plots compared with untreated plots. Despite this difference, manipulations of weeds did not lead to any significant changes in density of E. servus adults in corn. Further evidence suggested that a prominent external source of E. servus, other than field-bordering weeds, in the farmscape was likely driving densities in corn.}, number={2}, journal={Environmental Entomology}, publisher={Oxford University Press (OUP)}, author={Babu, Arun and Reisig, Dominic D and Walgenbach, James F and Heiniger, Ronnie W and Everman, Wesley}, year={2019}, month={Feb}, pages={444–453} }
 @article{tilley_heiniger_crozier_2019, title={Tiller Initiation and its Effects on Yield and Yield Components in Winter Wheat}, volume={111}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2018.07.0469}, abstractNote={Vegetative growth in the form of tillers is crucial to final yield in winter wheat (Triticum aestivum L.). To understand the impact management practices have on tiller initiation, a study was conducted using two seeding rates (1.9 × 10⁶ vs. 6.8 × 10⁶ ha–¹) and two N timing applications (single vs. split). Tillers initiated in the fall made up the majority of spikes compared to tillers initiated from 1 January to the start of jointing (GS 30). Tillers initiated in March at either seeding rate produced very few kernels spike–¹, low kernel weight, and contributed little to yield. At the high seeding rate, tillers initiated prior to 1 January were responsible for more than 87% of the grain yield. Tillers produced in January– February produced 5 to 11% of the final yield, while tillers produced in March contributed less than 2%. In contrast, at the low seeding rate tillers produced in January–February made up 20 to almost 60% of the final yield. Overall, this study shows the timing and rate of leaf initiation impacts yield and yield components. Earlier tillers have an advantage in that they have shorter periods of leaf development that result in more leaf area which in turn supports more kernel spike–¹ and heavier kernels, thus more grain weight per spike. Timing of N (single vs. split) application resulted in no significant impact on tiller development, spike number, kernel number, kernel weight, or grain yield.}, number={3}, journal={AGRONOMY JOURNAL}, author={Tilley, M. Scott and Heiniger, Ronnie W. and Crozier, Carl R.}, year={2019}, pages={1323–1332} }
 @article{molo_heiniger_boerema_carbone_2019, title={Trial Summary on the Comparison of Various Non-Aflatoxigenic Strains of Aspergillus flavus on Mycotoxin Levels and Yield in Maize}, volume={111}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2018.07.0473}, abstractNote={Core Ideas Biocontrol strains are effective at reducing AF levels in maize. Native and commercially available biocontrol strains are equally effective in reducing AF levels. Deploying strains of opposite mating types in combination can lead to the greatest reduction in AF contamination. The fungus Aspergillus flavus can contaminate maize ( Zea mays L.) by producing aflatoxins (AFs), secondary metabolites that have been shown to have adverse health impacts for humans and animals when ingested in large quantities or over extended lengths of time. The FDA strictly regulates that corn contaminated with more than 20 parts per billion (ppb) AFs cannot be marketed for human consumption; therefore, AFs cost US corn growers billions of dollars every year. Current methods to curb aflatoxin contamination in fields involve dense applications of non‐aflatoxigenic biological control (biocontrol) strains, either Afla‐Guard or AF36, that outcompete native strains and reduce toxicity levels throughout the field. This fungus is heterothallic and sexual reproduction occurs between isolates of opposite mating types, either MAT1−1 or MAT1−2. Both biocontrol strains are of a single mating type MAT1−2 . The implications of adding a strain of opposite mating type (MAT1−1) to this formulation are unknown. Here we examine the ability of native non‐aflatoxigenic strains applied singly and in combination to reduce AF concentrations in a cornfield in Rocky Mount, NC. We show that native, non‐aflatoxigenic A. flavus strains reduced aflatoxin levels and increased yield when compared with untreated controls. Moreover, the strain formulations that included sexually compatible MAT1−1 and MAT1−2 strains showed the greatest reduction in aflatoxin levels. We propose that using a combination of native isolates of opposite mating types reduces AF levels further than current biocontrol agents of a single mating‐type strain and could potentially provide a more long‐term form of control.}, number={2}, journal={AGRONOMY JOURNAL}, author={Molo, Megan S. and Heiniger, Ron W. and Boerema, Leah and Carbone, Ignazio}, year={2019}, pages={942–946} }
 @article{del pozo-valdivia_reisig_arellano_heiniger_2018, title={A case for comprehensive analyses demonstrated by evaluating the yield benefits of neonicotinoid seed treatment in maize (Zea mays L.)}, volume={110}, ISSN={["1873-6904"]}, DOI={10.1016/j.cropro.2017.10.021}, abstractNote={With increased scrutiny of the neonicotinoid class of chemistry and its negative impact on the pollinator community, ecological cost/benefit analyses of agronomic crops that use these insecticides are increasingly important. This study initially sought to address the question of yield benefit due to neonicotinoid seed treatment in maize (Zea mays L.), using North Carolina yield contest data from 2002 to 2006, the time period from initial neonicotinoid seed treatment adoption to nearly ubiquitous adoption. However, we recognized that several agronomic practices, including planting date, hybrid selection, and fertilization, could affect the yield of this crop; moreover, they could be collinear with one another and the analysis could be skewed by early adopters of new technology. Hence, we used all available data to compare among traditional approaches and a data-mining approach for analyzing the impact of neonicotinoid seed treatment on maize yield. At-planting insecticide treatment was not an important predictor of maize yield. When analyzed using the traditional approach (T-test), yields were significantly higher for fields planted with neonicotinoid treated seed compared to seed without neonicotinoid; however, data-mining approach (Decision tree analysis) that took into account other factors contributing to yield did not identify seed treatments as important. The contrast in these results highlights the need for future carefully designed studies that target to minimize inter- and intra-site variation; and include measurements of additional factors that may influence yield, such as seeding rate, tillage, and herbicide applications, as input variables that are largely lacking in current approaches on the subject.}, journal={CROP PROTECTION}, publisher={Elsevier BV}, author={Del Pozo-Valdivia, Alejandro I. and Reisig, Dominic D. and Arellano, Consuelo and Heiniger, Ron W.}, year={2018}, month={Aug}, pages={171–182} }
 @article{lee_aberle_anderson_anderson_baldwin_baltensperger_barrett_blumenthal_bonos_bouton_et al._2018, title={Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership}, volume={10}, ISSN={["1757-1707"]}, DOI={10.1111/gcbb.12493}, abstractNote={Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small‐scale and short‐term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long‐term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field‐scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm‐scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM‐ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country.}, number={10}, journal={GLOBAL CHANGE BIOLOGY BIOENERGY}, author={Lee, Do Kyoung and Aberle, Ezra and Anderson, Eric K. and Anderson, William and Baldwin, Brian S. and Baltensperger, David and Barrett, Michael and Blumenthal, Jurg and Bonos, Stacy and Bouton, Joe and et al.}, year={2018}, month={Oct}, pages={698–716} }
 @article{reisig_bacheler_herbert_heiniger_kuhar_malone_philips_tilley_2017, title={Cereal Leaf Beetle (Coleoptera: Chrysomelidae) Regional Dispersion and Relationship With Wheat Stand Denseness}, volume={46}, ISSN={["1938-2936"]}, DOI={10.1093/ee/nvx034}, abstractNote={Abstract Cereal leaf beetle, Oulema melanopus L., is a pest of small grains and the literature conflicts on whether it is more abundant in sparse or dense stands of wheat. Our objectives were to determine the impact of stand denseness on cereal leaf beetle abundance and to investigate the regional dispersion of cereal leaf beetles across North Carolina and Virginia. One-hundred twenty fields were sampled across North Carolina and Virginia during 2011 for stand denseness, and cereal leaf beetle eggs, larvae, and adults. Two small-plot wheat experiments were planted in North Carolina using a low and a high seeding rate. Main plots were split, with one receiving a single nitrogen application and one receiving two. Egg density, but not larva or adult density, was positively correlated with stand denseness in the regional survey. Furthermore, regional spatial patterns of aggregation were noted for both stand denseness and egg number. In the small-plot experiments, seeding rate influenced stand denseness, but not nitrogen application. In one experiment, egg densities per unit area were higher in denser wheat, while in the other experiment, egg densities per tiller were lower in denser wheat. Larvae were not influenced by any factor. Overall, there were more cereal leaf beetle eggs in denser wheat stands. Previous observations that sparse stands of wheat are more prone to cereal leaf beetle infestation can be attributed to the fact that sparser stands have fewer tillers, which increases the cereal leaf beetle to tiller ratio compared with denser stands.}, number={3}, journal={ENVIRONMENTAL ENTOMOLOGY}, publisher={Oxford University Press (OUP)}, author={Reisig, Dominic D. and Bacheler, Jack S. and Herbert, D. Ames and Heiniger, Ron and Kuhar, Thomas and Malone, Sean and Philips, Chris and Tilley, M. Scott}, year={2017}, month={Jun}, pages={425–433} }
 @article{besançon_heiniger_weisz_everman_2017, title={Grain Sorghum and Palmer Amaranth (Amaranthus palmeri) Response to Herbicide Programs and Agronomic Practices}, volume={31}, ISSN={0890-037X 1550-2740}, url={http://dx.doi.org/10.1017/WET.2017.53}, DOI={10.1017/WET.2017.53}, abstractNote={Weed control remains a major challenge for economically viable grain sorghum production in the southeastern United States due to crop sensitivity to weed competition during early growth stages. Field experiments were conducted in 2012 and 2013 to determine the effects of grain sorghum row spacing, population density, and herbicide programs on Palmer amaranth control, crop growth, and grain yield. Treatments included row spacings of 19, 38, and 76 cm; grain sorghum population densities of 99,000, 198,000, 297,000, and 396,000 plants ha-1; and three herbicide programs: (1) a nontreated control, (2) S-metolachlor at 1,410 g ai ha-1 plus atrazine at 1,820 g ha-1 PRE, and (3) S-metolachlor at 1,070 g ha-1 plus atrazine at 1,380 g ha-1 PRE followed by 2,4 D at 330 g ha-1 POST. Palmer amaranth control benefited from the addition of a POST herbicide and from crop density≥297,000 plants ha-1. Under weedy conditions, Palmer amaranth density was not affected by narrower row spacing or increased crop density, whereas its dry biomass was reduced by 33% with 19 and 38 compared to 76 cm rows, and by 43% with≥297,000 vs 99,000 plants ha-1. Row spacing had no effect on light interception by the crop canopy. However, crop density influenced canopy closure with maximum light interception occurring one and a half weeks earlier for density ≥297,000 plants ha-1. Yield increased by 18% for 19 vs 38 and 76 cm rows, whereas grain crop density had no effect. Overall, these results indicate that the combination of row spacing ≤30 cm and crop density ≥297,000 plants ha-1 provided at least 97% Palmer amaranth control in the absence of POST application and reduced its biomass by 32% in nontreated plots compared to 76 cm row spacing and crop density≤198,000 plants ha-1. Nomenclature: Atrazine; S-metolachlor; 2,4-D; Palmer amaranth; Amaranthus palmeri S. Wats.; sorghum, Sorghum bicolor (L.) Moench ssp. bicolor.}, number={6}, journal={Weed Technology}, publisher={Cambridge University Press (CUP)}, author={Besançon, Thierry E. and Heiniger, Ronnie W. and Weisz, Randy and Everman, Wesley J.}, year={2017}, month={Sep}, pages={781–792} }
 @article{howell_reisig_burrack_heiniger_2017, title={Impact of imidacloprid treated seed and foliar insecticide on Hessian fly abundances in wheat (Triticum aestivum L.)}, volume={98}, ISSN={["1873-6904"]}, DOI={10.1016/j.cropro.2017.03.007}, abstractNote={Wheat, Triticum aestivum L., is a major crop of economic importance throughout the United States. The Hessian fly, Mayetiola destructor (Say), is a common economically important pest, feeding on wheat in the larval stage through the southeastern US. It is a multi-voltine species, with generation number dependent on temperature. Growers rely on various management approaches such as resistant wheat varieties, crop rotation, timely plantings, and insecticide treatments to control this destructive pest. The objectives for this research were to show the efficacy of a common insecticide seed treatment (imidacloprid) and a common foliar insecticide spray (lambda-cyhalothrin) on Hessian fly abundance in wheat. Four experiments were conducted over two years in North Carolina, in order to manipulate Hessian fly abundance. Small plot studies were designed with whole plot treatments including non-treated and imidacloprid treated wheat seed, and subplots split with a semi-monthly foliar lambda-cyhalothrin application or no foliar insecticide. The number of Hessian fly eggs present on leaves, number of larvae, number of pupae, and tiller density were counted for the fall generation(s) and all plots were sprayed with foliar insecticide during the spring. Wheat seed treated with imidacloprid had fewer eggs, larvae, and pupae compared to other non-treated seed. With one exception during 2014, foliar spray applications did not reduce egg, larvae, and pupae abundance. Warmer temperatures during 2015 experiments provided conditions that extended Hessian fly presence, allowing multiple fall generations to infest wheat. Unlike 2014 experiments, foliar sprays in 2015 experiments provided some protection from Hessian fly.}, journal={CROP PROTECTION}, publisher={Elsevier BV}, author={Howell, F. C. and Reisig, D. D. and Burrack, H. J. and Heiniger, R.}, year={2017}, month={Aug}, pages={46–55} }
 @article{besancon_heiniger_weisz_everman_2017, title={Weed Response to Agronomic Practices and Herbicide Strategies in Grain Sorghum}, volume={109}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2016.06.0363}, abstractNote={Core Ideas High sorghum density and narrow row spacing reduce biomass of troublesome weeds. High spatial crop uniformity extends large crabgrass and sicklepod control over time. Optimized crop density and row width may limit the need for postemergence herbicide in sorghum. Sicklepod [ Senna obtusifolia (L.) H.S. Irwin & Barneby] and large crabgrass ( Digitaria sanguinalis L.) are ranked among the top 10 most common or troublesome weeds in grain sorghum [ Sorghum bicolor (L.) Moench] in the southeastern United States. Field studies conducted in North Carolina from 2012 to 2014 investigated the effects of three row widths, four sorghum populations, and three herbicide programs on weed control, density, biomass, and grain yield. Results indicated that 19‐ and 38‐cm rows provided greater sicklepod control 7 and 10 wk after planting (WAP) compared to 76 cm but had no effect on crabgrass control. Under weed‐controlled conditions, sorghum population ≥297,000 plants ha −1 allowed to maintain higher late‐season sicklepod and crabgrass control as compared to lower crop densities. In the weedy control, row spacing had no effect on weed density and biomass, whereas crop population ≥297,000 plants ha −1 reduced sicklepod density and biomass by 38 and 65%, respectively, compared to 99,000 plants ha −1 . Effect on crabgrass was less pronounced with density and biomass reduction by 18 and 45%, respectively, for 396,000 plants ha −1 compared to 99,000 plants ha −1 . In the absence of water stress, the highest grain yields were obtained with high spatial uniformity, corresponding to 19‐cm rows and sorghum population ≥297,000 sorghum plants ha −1 . Our results indicate that increased sorghum density associated with narrow rows may reduce the need for a postemergence (POST) herbicide but underscore the importance of a timely activated preemergence (PRE) treatment to efficiently control sicklepod and crabgrass.}, number={4}, journal={AGRONOMY JOURNAL}, author={Besancon, Thierry and Heiniger, Ronnie and Weisz, Randy and Everman, Wesley}, year={2017}, pages={1642–1650} }
 @article{gill_burks_staggenborg_odvody_heiniger_macoon_moore_barrett_rooney_2014, title={Yield Results and Stability Analysis from the Sorghum Regional Biomass Feedstock Trial}, volume={7}, ISSN={["1939-1242"]}, DOI={10.1007/s12155-014-9445-5}, number={3}, journal={BIOENERGY RESEARCH}, author={Gill, John R. and Burks, Payne S. and Staggenborg, Scott A. and Odvody, Gary N. and Heiniger, Ron W. and Macoon, Bisoondat and Moore, Ken J. and Barrett, Michael and Rooney, William L.}, year={2014}, month={Sep}, pages={1026–1034} }
 @article{blackman_deperno_heiniger_krachey_moorman_peterson_2011, title={Effects of crop field characteristics on nocturnal winter use by American woodcock}, volume={76}, ISSN={0022-541X}, url={http://dx.doi.org/10.1002/JWMG.254}, DOI={10.1002/jwmg.254}, abstractNote={Abstract}, number={3}, journal={The Journal of Wildlife Management}, publisher={Wiley}, author={Blackman, Emily B. and Deperno, Christopher S. and Heiniger, Ron W. and Krachey, Matthew J. and Moorman, Christopher E. and Peterson, M. Nils}, year={2011}, month={Nov}, pages={528–533} }
 @article{cahill_osmond_weisz_heiniger_2010, title={Evaluation of Alternative Nitrogen Fertilizers for Corn and Winter Wheat Production}, volume={102}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2010.0095}, abstractNote={As natural gas, and thus N fertilizer, prices increase, farmers are looking for ways to decrease N costs in farming operations. To potentially alleviate this cost burden, alternative synthetic N fertilizers are available as potential management tools for increasing crop yields and N use efficiency, and decreasing volatilization. In North Carolina specifically, little data exists on these new, synthetic N fertilizer products being marketed to farmers. Therefore, we undertook a study to compare them with aqueous urea ammonium nitrate (UAN) [(NH2)2CO, NH4NO3] during a 2‐yr field experiment. Corn (Zea mays L.) and wheat (Triticum aestivum L.) were grown in the three physiographic regions of North Carolina with four fertilizer sources (NutriSphere [Specialty Fertilizer Products, Leawood, KS], Environmentally Smart Nitrogen Polymer Coated Urea or ESN [Agrium Inc., Alberta, Canada] UCAN‐23 [Yara, Tampa, FL], and UAN) at up to six fertilizer rates. The use of the alternative products did not regularly produce more corn or wheat grain compared to UAN, while wheat straw yield was greater with NutriSphere, UCAN, and UAN compared to ESN in three of four site years. Also, an aerobic incubation experiment was performed to evaluated N release profiles of the fertilizers at 25°C. The study found that NutriSphere and UCAN release time was similarly to UAN, while ESN showed a slower release profile. However, any difference in release did not affect yields of spring planted corn, NutriSphere and ESN increased corn stover yields in 3 of 6 site‐years. In determining whether to use these alternative N fertilizer products, farmers should consider location, climatic conditions, and fertilizer costs in comparison to UAN.}, number={4}, journal={AGRONOMY JOURNAL}, author={Cahill, Sheri and Osmond, Deanna and Weisz, Randy and Heiniger, Ronnie}, year={2010}, pages={1226–1236} }
 @article{wall_weisz_crozier_heiniger_white_2010, title={Variability of the Illinois Soil Nitrogen Test across Time and Sampling Depth}, volume={74}, ISSN={["1435-0661"]}, DOI={10.2136/sssaj2009.0253}, abstractNote={There is potential for using the Illinois soil nitrogen test (ISNT) to improve N fertilizer recommendations for crops in the southeastern United States. The ISNT has been previously calibrated to predict N rates for corn (Zea mays L.) in North Carolina. This study evaluated the effects of sampling time, sampling depth, crop rotation, and fertilizer application on soil ISNT‐N during a 2‐yr period in the humid Coastal Plain and Piedmont regions of North Carolina. Ten sites were repeatedly sampled at 0‐ to 10‐, 10‐ to 20‐, and 20‐ to 30‐cm depths in fall, mid‐winter, and spring between October 2006 and May 2007. Illinois soil nitrogen test N, KCl‐extractable soil NO3–N and NH4–N, and soil organic matter (SOM) derived by loss‐on‐ignition (LOI) were evaluated at each sampling. Temporal changes in these soil parameters were evaluated for various crop rotations and N fertilizer applications. Soil ISNT‐N decreased with depth and showed significant variation with time at all three depths at all sites. Soil ISNT‐N was influenced by crop rotation and tillage but was not significantly affected by N fertilizer applications. Considering all sites together, ISNT‐N was well correlated with LOI; however, ISNT‐N was not correlated with LOI across time within sites. This suggests that the ISNT measured a fraction of SOM that behaved somewhat independently with time.}, number={6}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, publisher={Soil Science Society of America}, author={Wall, David P. and Weisz, Randy and Crozier, Carl R. and Heiniger, Ronnie W. and White, Jeffrey G.}, year={2010}, pages={2089–2100} }
 @inproceedings{havlin_heiniger_2009, title={A variable-rate decision support tool}, volume={10}, DOI={10.1007/s11119-009-9121-5}, number={4}, booktitle={Precision Agriculture}, author={Havlin, J. L. and Heiniger, Ronnie}, year={2009}, pages={356–369} }
 @article{yang_wilkerson_buol_bowman_heiniger_2009, title={Estimating Genetic Coefficients for the CSM-CERES-Maize Model in North Carolina Environments}, volume={101}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2008.0234x}, abstractNote={CSM‐CERES‐Maize has been extensively used worldwide to simulate corn growth and grain production, but has not been evaluated for use in North Carolina. The objectives of this study were to calibrate CSM‐CERES‐Maize soil parameters and genetic coefficients using official variety trial data, evaluate model performance in North Carolina, and determine the suitability of the fitting technique using variety trial data for model calibration. The study used yield data for 53 maize genotypes collected from multiple locations over a 10‐yr period. A stepwise calibration procedure was utilized: (i) two genetic coefficients which determine anthesis and physiological maturity dates were adjusted based on growing degree day requirements for each hybrid; and (ii) plant available soil water and rooting profile were adjusted iteratively with two other genetic coefficients affecting yield. Cross validation was used to evaluate the suitability of this approach for estimating soil and genetic coefficients. The root mean squared errors of prediction (RMSEPs) were similar to fitting errors. Results indicate that CSM‐CERES‐Maize can be used in North Carolina to simulate corn growth under nonlimiting N conditions and variety trial data can be used for estimating genetic coefficients. Hybrid average simulated yields matched measured yields well across a wide range of environments, and simulated hybrid yield rankings were in close agreement with rankings based on measured yields. Data from several site‐years could not be used in fitting genetic coefficients due to large root mean squared errors. In some cases, this could be attributed to a weather event, such as a late‐season hurricane.}, number={5}, journal={AGRONOMY JOURNAL}, author={Yang, Zhengyu and Wilkerson, Gail G. and Buol, Gregory S. and Bowman, Daryl T. and Heiniger, Ronnie W.}, year={2009}, pages={1276–1285} }
 @article{sripada_farrer_weisz_heiniger_white_2007, title={Aerial color infrared photography to optimize in-season nitrogen fertilizer recommendations in winter wheat}, volume={99}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2006.0258}, abstractNote={Remote sensing in the form of aerial color infrared (CIR) photography has been shown to be a useful tool for in‐season N management in winter wheat (Triticum aestivum L.). The objectives of this study were (i) to develop a methodology for predicting in‐season optimum fertilizer N rates for winter wheat at growth stage (GS) 30 directly from aerial CIR photography and (ii) to quantify how the relationships between these optimum N rates and spectral indices respond to different levels of biomass of the wheat crop. Field studies were conducted for three winter wheat growing seasons (2002–2004) over a wide range of soil conditions across North Carolina using a split‐split plot randomized complete block design. Different planting date–seeding rate (PDSR) combinations were applied to create a range of biomass levels at GS 30. Different levels of N were applied at GS 25 (N25) to create a range of N supply and winter wheat radiance, and at GS 30 (N30) to measure grain yield response to N30. Aerial CIR photographs were obtained at each site at GS 30 before N applications. Significant biomass response to PDSR and yield response to N25 and N30 were observed. Optimum N30 ranged from 0 to 124 kg ha−1 with a mean of 55 kg ha−1. Better prediction of optimum N30 rates were obtained with spectral indices calculated relative to high‐N reference strips compared to absolute bands or spectral indices. Biomass measured at GS 30 influenced the strength of the relationship between optimum N30 and spectral indices. When the GS‐30 biomass was >1000 kg ha−1, the best predictor of optimum N30 (R2 = 0.85) was a quadratic model based on measured winter wheat radiance relative to mean radiance in the G band for the high N reference strip (Rel GS).}, number={6}, journal={AGRONOMY JOURNAL}, publisher={American Society of Agronomy}, author={Sripada, Ravi P. and Farrer, Dianne C. and Weisz, Randy and Heiniger, Ronnie W. and White, Jeffrey G.}, year={2007}, pages={1424–1435} }
 @article{williams_crozier_white_heiniger_sripada_crouse_2007, title={Illinois soil nitrogen test predicts southeastern US corn economic optimum nitrogen rates}, volume={71}, ISSN={["0361-5995"]}, DOI={10.2136/sssaj2006.0135}, abstractNote={An accurate and quick soil N test is needed for N fertilizer recommendations for corn (Zea mays L.) for the humid southeastern USA. The Illinois soil N test (ISNT) has been used to distinguish fertilizer-responsive from unresponsive sites in Illinois. We determined relationships between economic optimum N rates (EONR) and ISNT levels in representative southeastern soils in 35 N-response trials in the Piedmont (n = 4) and Middle (n = 8) and Lower (n = 23) Coastal Plains of North Carolina from 2001 to 2004. The ISNT was strongly correlated with EONR for well or poorly drained sites (r 2 = 0.87 [n = 20] and 0.78 [n = 10], respectively); data were insuffi cient for establishing correlations for very poorly drained or severely drought-stressed sites. Expressing ISNT on a mass per unit volume basis vs. EONR improved the correlations slightly (r 2 = 0.88 and 0.79 for well and poorly drained sites, respectively), but these improvements would not justify the necessary soil bulk density determinations. Regressions of ISNT vs. minimum, average, and maximum EONR based on different N-fertilizer cost /corn price ratios (11.4:1, 7.6:1, and 5:1, respectively) showed strong correlations with EONR for well-drained sites (r 2 = 0.77, 0.87, and 0.87, respectively) and poorly drained sites (r 2 = 0.84, 0.78, 0.70, respectively). The ISNT–EONR correlations were different among the cost/price ratios for well-drained sites, but not different for poorly drained sites. Because ISNT predicted EONR robustly to different cost/price ratios, ISNT has the potential to modify or replace current N recommendation methods for corn. Abbreviations: EONR, economic optimum nitrogen rate; HM, humic matter; ISNT, Illinois soil nitrogen test; RYE, realistic yield expectation.}, number={3}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, publisher={Soil Science Society of America}, author={Williams, Jared D. and Crozier, Carl R. and White, Jeffrey G. and Heiniger, Ronnie W. and Sripada, Ravi P. and Crouse, David A.}, year={2007}, pages={735–744} }
 @article{weisz_sripada_heiniger_white_farrer_2007, title={In-season tissue testing to optimize soft red winter wheat nitrogen fertilizer rates: Influence of wheat biomass}, volume={99}, ISSN={["0002-1962"]}, DOI={10.2134/agronj2006.0112}, abstractNote={In the southeastern USA, soft red winter wheat (Triticum aestivum L.) N fertilizer recommendations are based on growth stage (GS) 30 tissue testing and models that assume that the relationship between tissue N concentration (Ncon) and optimum N fertilizer rates (MaxN30) is stable across fields differing in GS‐30 biomass. However, previous research has indicated this may not be the case. Consequently, it was critical to re‐evaluate these models. Using a split‐split plot design, six experiments were conducted in North Carolina between 2002 and 2004. Main plots were planting date–seeding rate combinations that produced wheat with different GS‐30 biomass. Subplots and sub‐subplots were five N rates applied at GS‐25 and GS‐30, respectively. Wheat yield was responsive to fertilizer N at all site‐years. The overall relationship between MaxN30 and Ncon was weak (r2 = 0.43). The relationship between MaxN30 and N uptake (Ncon × biomass) was weaker (r2 = 0.27). However, when the data were divided into different biomass classes, the overall model improved (R2 = 0.75). For biomass < 340 kg ha−1, the Ncon at which no additional N fertilizer was required (Ncritical) was 70.0 g N kg−1. As biomass increased, Ncritical decreased to 33.2 g N kg−1. Intermediate classes had slopes of MaxN30 versus Ncon and Ncritical values that were similar to those previously reported. This study indicates that to use tissue testing to determine N fertilizer recommendations across a range of GS‐30 biomass conditions requires information regarding dry matter biomass.}, number={2}, journal={AGRONOMY JOURNAL}, publisher={American Society of Agronomy}, author={Weisz, Randy and Sripada, Ravi P. and Heiniger, Ronnie W. and White, Jeffrey G. and Farrer, Dianne C.}, year={2007}, pages={511–520} }
 @article{sripada_heiniger_white_crozier_meijer_2006, title={Attempt to validate a remote sensing-based late-season corn nitrogen requirement prediction system}, ISBN={1543-7833}, journal={Crop Management}, author={Sripada, R. P. and Heiniger, R. W. and White, J. G. and Crozier, C. R. and Meijer, A. D.}, year={2006}, pages={1} }
 @article{farrer_weisz_heiniger_murphy_pate_2006, title={Delayed harvest effect on soft red winter wheat in the southeastern USA}, volume={98}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2005.0211}, abstractNote={Harvest of soft red winter wheat (Triticum aestivum L.) in the southeastern USA can be delayed because of inclement weather or other unforeseen problems. Our objectives were to determine the impact of delaying harvest beyond grain ripeness (135 g kg−1 grain moisture content) on yield, test weight, grain protein, and 20 milling and baking quality parameters, and to determine if these impacts were correlated with environmental conditions occurring between grain ripeness and harvest. In 2001 and 2002, a total of six trials were conducted where treatments consisted of a timely harvest at grain ripeness and a delayed harvest, 8 to 19 d later. Yield was reduced by up to ∼900 kg ha−1 due to delayed harvest, with yield losses negatively related to total precipitation and positively related to minimum daily temperatures (R2 = 0.99) during the delay interval, indicating that dry and warm environments increased yield losses. Test weight reductions up to ∼115 kg m−3 were seen and were linearly related to the number of precipitation events (r2 = 0.93) between harvests. Grain protein was not affected by delayed harvest. Of the milling and baking quality parameters measured, grain and flour falling number, clear flour percentage, grain deoxynivalenol (DON), and farinograph breakdown times were negatively affected by delayed harvest. Lower falling numbers and higher levels of DON are consistent with the high humidity and rainfall typical of the southeastern USA wheat harvest and are problematic for millers. Decreased farinograph breakdown times can be a problem for bakers.}, number={3}, journal={AGRONOMY JOURNAL}, author={Farrer, Dianne and Weisz, Randy and Heiniger, Ronnie and Murphy, J. Paul and Pate, Michael H.}, year={2006}, pages={588–595} }
 @article{sripada_heiniger_white_weisz_2005, title={Aerial color infrared photography for determining late-season nitrogen requirements in corn}, volume={97}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2004.0314}, abstractNote={Fast and accurate methods of determining in‐season corn (Zea mays L.) N requirements are needed to provide more precise and economical management and potentially decrease groundwater N contamination. The objectives of this study were (i) to determine if there is a response to late‐season N applied to corn at pretassel (VT) under irrigated and nonirrigated conditions, and (ii) to develop a methodology for predicting in‐season N requirement for corn at the VT stage using aerial color infrared (CIR) photography. Field studies were conducted for 3 yr over a wide range of soil conditions and water regimes in the North Carolina Coastal Plain. Different fertilizer N rates were applied (i) at planting (NPL) to create a range of N supply, corn color, and near‐infrared (NIR) radiance; and (ii) at VT (NVT) to measure yield response to NVT. Aerial CIR photographs were obtained for each site at VT before N application. Significant grain yield responses to NPL and NVT were observed. Economic optimum NVT rates ranged from 0 to 224 kg ha−1 with a mean of 104 kg ha−1. Better prediction of economic optimum NVT rates was obtained with spectral band combinations rather than individual bands, and improved when calculated relative to high‐N reference strips measured at VT. The best predictor of economic optimum NVT (R
2 = 0.67) was a linear‐plateau model based on corn color and NIR radiance expressed using the Green Difference Vegetation Index (GDVI) relative to high‐N reference strips (Relative GDVI, RGDVI).}, number={5}, journal={AGRONOMY JOURNAL}, publisher={American Society of Agronomy}, author={Sripada, RP and Heiniger, RW and White, JG and Weisz, R}, year={2005}, pages={1443–1451} }
 @article{flowers_weisz_heiniger_osmond_crozier_2004, title={In-season optimization and site-specific nitrogen management for soft red winter wheat}, volume={96}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2004.0124}, abstractNote={application up to 70% without a reduction in grain yield compared to a grower’s practice. Site-specific N management based on an in-season assessment of Stone et al. (1996) used an on-the-go sensor measurcrop N status may offer producers increased grain yield, profitability, ing plant N spectral index to create submeter siteand spring N fertilizer use efficiency (SNUE). The goal of this study specific N management units based on an estimate of was to determine the distinct contributions of (i) in-season N rate optimization and (ii) site-specific N management. Our objective was in-season crop N status in wheat. This site-specific N to compare site-specific and field-specific N management with typical management system reduced N fertilizer by 32 and 57 growers’ practices to determine if site-specific N management (i) kg N ha 1 at two of three sites without a reduction in increased soft red winter wheat (Triticum aestivum L.) grain yield, grain yield compared with a typical grower’s practice. (ii) reduced N inputs, (iii) increased SNUE, and (iv) reduced withinThey also reported that the site-specific N application field grain yield variability. Research was conducted at eight sites in reduced spatial variation in wheat forage and grain yield 2000, 2001, and 2002. A randomized complete block design with two compared with the grower’s practice. or five N management systems was used at two and six sites, respecSimilarly, Raun et al. (2002) used a multispectral optitively. Site-specific management did not improve grain yield compared cal sensor to create 1-m2 site-specific N management with field-specific management when based on the same in-season units in wheat. A N fertilizer optimization algorithm estimation of optimum N rates. At sites where site-specific or field(NFOA) that estimates in-season crop N status and specific systems were compared with typical growers’ practices, grain potential grain yield was used to adjust N rates. They yield benefits of in-season N optimization (up to 2267 kg ha 1) were reported that by using NFOA, it might be possible to apparent. For grain yield, in-season optimization of N rate was more important than site-specific management. A large reduction in N inset more efficient and profitable fertilization levels and puts (up to 48.6%) was also attributed to in-season N rate optimizaincrease N use efficiency compared with typical growtion. After incorporating in-season optimization, a further reduction ers’ practices. in N inputs (up to 19.6%) was possible through site-specific applicaMulla et al. (1992), Bhatti et al. (1998), Stone et al. tion. Site-specific N application maximized SNUE compared with (1996), and Raun et al. (2002) compared site-specific N either field-specific or typical growers’ practices at all sites and reduced management based on either a preor in-season estiwithin-field grain yield variance at four sites. mate of the crop’s N requirement to a typical grower’s practice. Consequently, the reduction in N rates compared with growers’ practices might not have been the S N management is the adjusting of withinresult of site-specific application but could instead be field N fertilizer rates based on spatially variable due to using a preor in-season estimation of the crop’s factors that affect optimum N rate (Sawyer, 1994). This N requirement. practice may offer producers the ability to increase grain In the southeastern USA, Scharf and Alley (1993), yield, profitability, and N fertilizer efficiency by applyAlley et al. (1994), Weisz and Heiniger (2000), and ing N only where required for optimum plant growth. Weisz et al. (2001) developed a field-specific N manageSite-specific management may also be environmentally ment system for soft red winter wheat based on an inbeneficial to producers. season evaluation of the crop’s N requirement (Fig. 1). Mulla et al. (1992) created site-specific management This system first determines the whole-field tiller density units (18.3 m by 564–655 m) based on preseason soil N at Zadoks’ Growth Stage (GS) 25 (Zadoks et al., 1974). (nitrate N and ammonium N) tests and available soil When GS-25 tiller density is below a critical threshold water content. Similarly, Bhatti et al. (1998) created (540 tillers m 2), a GS-25 N application is made to insite-specific N management units based on crop produccrease tiller development (Ayoub, 1974; Power and tivity. In both cases, site-specific N reduced N fertilizer Alessi, 1978; Lutcher and Mahler, 1988; Scharf and Alley, 1993; Weisz et al., 2001). A GS-25 N application can stimulate tiller development in southeastern areas M. Flowers, USDA-ARS, Air Quality–Plant Growth and Dev. Res. because winter wheat does not enter a dormant state Unit, 3908 Inwood Rd., Raleigh, NC 27603; R. Weisz, Dep. of Crop in these southern latitudes. If GS-25 tiller density is Sci., North Carolina State Univ., Box 7620, Raleigh, NC 27695-7620; above the threshold, a GS-25 N application is not necesR. Heiniger, Dep. of Crop Sci, North Carolina State Univ., Vernon James Res. and Ext. Cent., 207 Research Rd., Plymouth, NC 27692; sary. At GS 30, a field-averaged tissue test is used to D. Osmond, Dep. of Soil Sci., North Carolina State Univ., Box 7619, optimize N application rates (Alley et al., 1994). This Raleigh, NC 27695-7619; and C. Crozier, Dep. of Soil Sci., North system resulted in an increase in estimated profit of $73 Carolina State Univ., Vernon James Res. and Ext. Cent., 207 Research ha 1 across 20 site-years (Scharf and Alley, 1993). Rd., Plymouth, NC 27692. Received 5 Dec. 2002. *Corresponding author (mike_flowers@ncsu.edu). While this system (Fig. 1) has been tested and adopted Published in Agron. J. 96:124–134 (2004).  American Society of Agronomy Abbreviations: GS, growth stage; SNUE, spring nitrogen fertilizer use efficiency. 677 S. Segoe Rd., Madison, WI 53711 USA}, number={1}, journal={AGRONOMY JOURNAL}, author={Flowers, M and Weisz, R and Heiniger, R and Osmond, D and Crozier, C}, year={2004}, pages={124–134} }
 @article{flowers_weisz_heiniger_tarleton_meijer_2003, title={Field validation of a remote sensing technique for early nitrogen application decisions in wheat}, volume={95}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2003.0167}, abstractNote={Studies have shown that winter wheat (Triticum aestivum L.) tiller density at growth stage 25 (GS 25) can be used to determine when a GS-25 N application is needed. However, determining GS-25 tiller density is difficult and time consuming. Color infrared aerial photographs have been successfully used to predict GS-25 tiller density. The objective of this study was to validate a previously reported remote sensing technique to predict GS-25 tiller density based on near-infrared (NIR) digital counts and within-field tiller density references across a wide range of environments. The NIR remote sensing technique was evaluated through linear regression and quadrant plot analysis to determine the accuracy of GS-25 tiller density predictions and GS-25 N application decisions based on a critical GS-25 tiller density threshold. The impact of different wheat varieties, soil colors, and weed populations were also evaluated through covariate analysis using 10 site-years of data. At three site-years, a randomized complete block design with three varieties and either two or three seeding rates was used. At these site-years, variety had a significant influence on spectral measurements. Seven additional site-years had a single variety and seeding rate. The NIR remote sensing technique was found to account for 76% of the variation between predicted and measured GS-25 tiller density across 10 site-years of data. Accurate GS-25 N application decisions were made 85.5% of the time by the NIR remote sensing technique across a wide range of environments including six soil types, six wheat varieties, and two systems.}, number={1}, journal={AGRONOMY JOURNAL}, author={Flowers, M and Weisz, R and Heiniger, R and Tarleton, B and Meijer, A}, year={2003}, pages={167–176} }
 @article{weisz_heiniger_white_knox_reed_2003, title={Long-term variable rate lime and phosphorus application for Piedmont no-till field crops}, volume={4}, ISBN={1385-2256}, DOI={10.1023/a:1024908724491}, number={3}, journal={Precision Agriculture}, author={Weisz, R. and Heiniger, Ronnie and White, Jeffrey and Knox, B. and Reed, L.}, year={2003}, pages={311} }
 @article{flowers_weisz_heiniger_2003, title={Quantitative approaches for using color infrared photography for assessing in-season nitrogen status in winter wheat}, volume={95}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2003.1189}, abstractNote={Due to the timing and rates of N applications in wheat (Triticum aestivum L.), the potential exists for high N loading to the environment. Plant tissue tests offer growers the ability to determine in‐season N status, and to optimize N applications and N use efficiency. However, sampling and N analysis can be costly, difficult, and time consuming. Remote sensing may offer a solution to these problems. The objectives of this study were to determine (i) if remote sensing could be used to estimate in‐season N status, (ii) if within‐field calibration would improve the ability of remote sensing to estimate crop N status, and (iii) if optimum N rates could be estimated using remote sensing. Research was conducted in 1999 to 2001 at eight sites. Two sites had randomized complete block designs with variety, seeding rate, and N rate as treatments. Six sites had a single seeding rate and wheat variety. Biomass was found to influence spectral measurements of in‐season N status. A strong relationship between the normalized difference vegetation index (NDVI) and growth stage (GS)‐30 whole‐plant N concentration (R2 = 0.69) and GS‐30 N uptake (R2 = 0.61) was found. Within‐field calibration did not improve the estimation of in‐season N status by NDVI. While it was possible to use NDVI to estimate GS‐30 N uptake, predicted N fertilizer rates based on N uptake were highly unreliable. However, NDVI reliably predicted GS‐30 N fertilizer rates based on whole‐plant N concentration for wheat that had mean GS‐30 biomass values >1000 kg ha−1}, number={5}, journal={AGRONOMY JOURNAL}, author={Flowers, M and Weisz, R and Heiniger, R}, year={2003}, pages={1189–1200} }
 @article{heiniger_mcbride_clay_2003, title={Using soil electrical conductivity to improve nutrient management}, volume={95}, ISSN={["0002-1962"]}, DOI={10.2134/agronj2003.0508}, number={3}, journal={AGRONOMY JOURNAL}, author={Heiniger, RW and McBride, RG and Clay, DE}, year={2003}, pages={508–519} }
 @article{heiniger_havlin_crouse_kvien_t._2002, title={Seeing is believing: The role of field days and tours in precision agriculture education}, volume={3}, ISBN={1385-2256}, number={4}, journal={Precision Agriculture}, author={Heiniger, R. W. and Havlin, J. L. and Crouse, D. A. and Kvien, C. and T., Knowles.}, year={2002}, pages={309} }
 @article{weisz_crozier_heiniger_2001, title={Optimizing nitrogen application timing in no-till soft red winter wheat}, volume={93}, ISSN={["0002-1962"]}, DOI={10.2134/agronj2001.932435x}, abstractNote={As no‐till acreage increases, N management guidelines need re‐examination due to the potential effects of surface residue on N transformations and crop development. Our objectives were to determine: (i) if N applied at Zadok's Growth Stage (GS) 25 improves grain yield of no‐till winter wheat (Triticum aestivum L.), (ii) if any yield increase was the result of increased spring tillering, and (iii) if there is a critical tiller density above which N application at GS‐25 in no‐till wheat was not required. Research was conducted at three sites in North Carolina with seven site‐years between fall 1996 and spring 1999. A continuum of GS‐25 tiller densities was generated (161‐1774 tillers m−2) by planting at different seeding rates and dates in a randomized complete block design. Five N treatments were applied at GS‐25, and three were applied at GS‐30. Tillering response to early spring N, yield, and yield components were measured. increasing early spring N rates resulted in higher tiller densities at GS‐30, and GS‐25 tiller density was a significant covariate. With GS‐25 tiller densities >550 tillers m−2, yields were higher when all N was applied at GS‐30. In years without spring freezes, wheat with <550 tillers m−2 achieved optimum yields when spring N was applied at GS‐25. Manipulating the timing of spring N application can optimize early spring tillering and yield component formation.}, number={2}, journal={AGRONOMY JOURNAL}, author={Weisz, R and Crozier, CR and Heiniger, RW}, year={2001}, pages={435–442} }
 @article{flowers_weisz_heiniger_2001, title={Remote sensing of winter wheat tiller density for early nitrogen application decisions}, volume={93}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2001.934783x}, abstractNote={There is increasing evidence that scouting of winter wheat (Triticum aestivum L.) fields to determine tiller density at Growth Stage (GS) 25 is useful in deciding if N should be applied. However, to obtain an accurate average of field tiller density, frequent and intensive measurements must be made. A solution to this problem may be remote sensing. The objectives of this study were to determine (i) if a spectral index or digital counts in the near infrared (NIR), red (R), green (G), or blue (B) wavelengths could be used to estimate GS‐25 tiller density across environments and (ii) if the inclusion of within‐field references would improve the estimation of GS‐25 tiller density for determining N recommendations. Research was conducted at four site‐years in 1998 and 1999 using two wheat varieties. At three locations, a randomized replicated strip‐plot design with three seeding rates was used. The fourth location was an on‐farm test with one seeding rate. Spectral indices and individual NIR, R, G, and B digital counts were tested for correlation with tiller density at each site. Tiller density at GS 25 and NIR digital counts were found to be consistently correlated (0.67 ≤ r ≤ 0.87). The inclusion of within‐field tiller density references resulted in a high correlation (r = 0.88) between relative tiller density and relative NIR digital counts across environments. Using relative NIR digital counts to predict tiller density would have resulted in the correct N recommendation 82% of the time.}, number={4}, journal={AGRONOMY JOURNAL}, author={Flowers, M and Weisz, R and Heiniger, R}, year={2001}, pages={783–789} }
 @article{flowers_weisz_heiniger_2000, title={Aerial photographic determination of nitrogen application timing and rate recommendations in winter wheat}, journal={Proceedings of the 5th International conference on precision agriculture, Bloomington, Minnesota, USA, 16-19 July, 2000}, publisher={Madison, WI : Precision Agriculture Center, University of Minnesota, ASA-CSSA-SSSA}, author={Flowers, M. and Weisz, R. and Heiniger, R.}, year={2000}, pages={1} }
 @article{crouse_havlin_mcbride_white_heiniger_weisz_roberson_2000, title={Precision farming education at NC State University}, journal={Proceedings of the 5th International conference on precision agriculture, Bloomington, Minnesota, USA, 16-19 July, 2000}, publisher={Madison, WI : Precision Agriculture Center, University of Minnesota, ASA-CSSA-SSSA}, author={Crouse, D. A. and Havlin, J. L. and McBride, R. G. and White, J. G. and Heiniger, R. and Weisz, R. and Roberson, G.}, year={2000}, pages={1} }
 @article{jenkins_crouse_mikkelsen_heiniger_2000, title={Spatial variability of phosphorus retention capacities for various fields}, journal={Proceedings of the 5th International conference on precision agriculture, Bloomington, Minnesota, USA, 16-19 July, 2000}, publisher={Madison, WI : Precision Agriculture Center, University of Minnesota, ASA-CSSA-SSSA}, author={Jenkins, J. R. and Crouse, D. A. and Mikkelsen, R. L. and Heiniger, R. W.}, year={2000}, pages={1} }
 @inproceedings{robert_crouse_mikkelsen_heiniger_robarge_2000, title={Spatial variability of soil pH, phosphorus, copper and zinc in fields receiving long-term applications of animal manure}, number={2000}, booktitle={Animal, agriculture and food processing waste: 8th Symposium: American Society of Agriculture Engineers, 2000}, publisher={St. Joseph, Michigan: American Society of Agricultural Engineers}, author={Robert, B. and Crouse, D.A. and Mikkelsen, R.L. and Heiniger, R. and Robarge, W.}, year={2000}, pages={597–601} }
 @article{heiniger_meijer_2000, title={Why variable rate application of lime has increased grower profits and acceptance of precision agriculture in the southeast}, journal={Proceedings of the 5th International conference on precision agriculture, Bloomington, Minnesota, USA, 16-19 July, 2000}, publisher={Madison, WI : Precision Agriculture Center, University of Minnesota, ASA-CSSA-SSSA}, author={Heiniger, R. W. and Meijer, A. J.}, year={2000}, pages={1} }
 @article{thurman_heiniger_1999, title={Evaluation of variable rate Pix (Mepiquat Chloride) application by soil type}, volume={2}, number={1999}, journal={Beltwide Cotton Conferences. Proceedings}, author={Thurman, M. E. and Heiniger, R. W.}, year={1999}, pages={524–526} }
 @article{williams_delano_heiniger_vanderlip_llewelyn_1999, title={Replanting strategies for grain sorghum under risk}, volume={60}, ISSN={["0308-521X"]}, DOI={10.1016/S0308-521X(99)00024-4}, abstractNote={Risk analysis of replanting strategies for grain sorghum at three Kansas locations was conducted using stochastic dominance techniques. Yield data were simulated for seven planting dates, six seeding rates or target plant populations, and three maturity classes over a 33-year period using weather data for each year at each location. The results showed that optimal planting dates, seeding rates, and maturity classes vary by location and risk preference. In northeast and southcentral Kansas, planting at later rather than earlier dates was preferred as risk aversion increased. In southwest Kansas, generally no change occurred in the preferred strategy as the level of risk aversion increased. Early- and medium-maturing hybrids and low-to-moderate seeding rates often were selected. Late-maturing hybrids never were selected by risk-averse managers. The degree of risk aversion did not significantly affect the selection of a replanting strategy for southcentral and southwest Kansas, but did for northeast Kansas. However, whether managers replanted immediately or delayed, replanting varied with the replanting decision date and degree of risk aversion. Replanting on the first replanting decision date in southwest Kansas rather than delaying 2 weeks or more was preferred by all risk-averse managers. More strongly risk-averse managers in the northeast and all risk-averse producers in southcentral Kansas preferred to delay replanting of damaged stands, in some cases by 2–4 weeks after the decision date. Results also showed that when a stand was damaged late in the season, the expected yield from the damaged stand had to be lower than that from a stand damaged early in the season in order for replanting to occur. Price changes had only minor impacts on the preferred replanting strategies. A higher crop price caused replanting to occur more often, because the yield reduction of a damaged stand required for replanting to be economically feasible grew smaller as the price increased.}, number={2}, journal={AGRICULTURAL SYSTEMS}, author={Williams, JR and DeLano, DR and Heiniger, RW and Vanderlip, RL and Llewelyn, RV}, year={1999}, month={May}, pages={137–155} }
 @article{thurman_heiniger_1998, title={Using GPS to scout cotton for variable rate PIX (Mepiquat chloride) application}, volume={2}, number={1998}, journal={Beltwide Cotton Conferences. Proceedings}, author={Thurman, M. E. and Heiniger, R. W.}, year={1998}, pages={1499–1502} }
 @article{heiniger_1998, title={Variable rate nutrient management for corn-wheat-soybean cropping systems}, volume={82}, number={4}, journal={Better Crops With Plant Food}, author={Heiniger, R. W.}, year={1998}, pages={11} }
 @article{heiniger_vanderlip_welch_1997, title={Developing guidelines for replanting grain sorghum .1. Validation and sensitivity analysis of the SORKAM sorghum growth model}, volume={89}, ISSN={["0002-1962"]}, DOI={10.2134/agronj1997.00021962008900010012x}, abstractNote={Abstract}, number={1}, journal={AGRONOMY JOURNAL}, author={Heiniger, RW and Vanderlip, RL and Welch, SM}, year={1997}, pages={75–83} }
 @article{heiniger_vanderlip_welch_muchow_1997, title={Developing guidelines for replanting grain sorghum .2. Improved methods of simulating caryopsis weight and tiller number}, volume={89}, ISSN={["0002-1962"]}, DOI={10.2134/agronj1997.00021962008900010013x}, abstractNote={Abstract}, number={1}, journal={AGRONOMY JOURNAL}, author={Heiniger, RW and Vanderlip, RL and Welch, SM and Muchow, RC}, year={1997}, pages={84–92} }
 @article{heiniger_vanderlip_williams_welch_1997, title={Developing guidelines for replanting grain sorghum .3. Using a plant growth model to determine replanting options}, volume={89}, ISSN={["0002-1962"]}, DOI={10.2134/agronj1997.00021962008900010014x}, abstractNote={Abstract}, number={1}, journal={AGRONOMY JOURNAL}, author={Heiniger, RW and Vanderlip, RL and Williams, JR and Welch, SM}, year={1997}, pages={93–100} }