@article{vann_reberg-horton_crozier_place_2018, title={Effect of Soybean Maturity, Crimson Clover Seeding Method, and Seeding Rate on Clover Biomass and Nitrogen Content}, volume={110}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2018.02.0118}, abstractNote={Core Ideas
Crimson clover seeding following the last cultivation of soybeans in July into MG3 to MG5 soybeans did not result in any substantial crimson clover growth in both years.
After harvest seeding into MG3 and MG4 soybean and aerial seeding into MG4 and MG5, soybean produced substantial clover N content ranging from 76 to 107 kg ha−1.
After harvest seeding behind MG5 soybeans reduced clover N content because late cover crop establishment restricted biomass production.
Seeding rate had no effect on clover biomass, clover N content, or corn yield for both drilled and aerially‐seeded crimson clover.
Timely crimson clover (Trifolium incarnatum L.) establishment is a management challenge for producers in the southeastern United States. Aerial seeding methods and the use of early maturing soybeans may allow for earlier crimson clover establishment and potentially increase nitrogen contributions to the following crop. A soybean (Glycine max L.)–crimson clover–corn (Zea mays L.) rotation experiment was conducted in Goldsboro, NC from 2006 to 2008. Three crimson clover seeding methods were evaluated: aerial seeding after last soybean cultivation, aerial application before soybean leaf drop, and after‐harvest drill seeding. Each seeding method was evaluated in three soybean maturity groups (MG; 3, 4, 5) and contained three crimson clover seeding rates (22, 39, 56 kg ha−1). Clover biomass accumulation, clover N content, and corn yield were determined. Crimson clover seeding following the last cultivation of soybeans into MG3, MG4, and MG5 did not result in any substantial crimson clover growth. After harvest seeding into MG3 and MG4 soybean residue and aerial seeding prior to soybean leaf drop into MG4 and MG5 soybean produced substantial clover N content ranging from 76 to 107 kg ha−1. After‐harvest seeding behind MG5 soybeans reduced clover N content likely because late cover crop establishment restricted biomass production. Seeding rate had no effect on clover biomass, clover N content, or corn yield. An independent crimson clover aerial seeding rate experiment conducted from 2006 to 2008 in Goldsboro, NC also confirmed no effect of crimson clover seeding rate on clover biomass or N content.}, number={5}, journal={AGRONOMY JOURNAL}, author={Vann, R. A. and Reberg-Horton, S. C. and Crozier, C. R. and Place, G. T.}, year={2018}, pages={1829–1835} }
 @article{place_reberg-horton_carter_smith_2011, title={Effects of Soybean Seed Size on Weed Competition}, volume={103}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2010.0195}, abstractNote={Organic soybean [Glycine max (L.) Merr.] producers must rely on various, nonherbicidal tactics for weed management. Increased soybean seed size may be one method to increase the competitiveness of the soybean canopy. Soybean varieties Hutcheson, NC‐Roy, and NC‐Raleigh were separated into four or five seed size classes. Seed sizes ranged from 5.15 to 6.75 mm diam. This range of seed size resulted in seed weights of 10 to 20 g per 100 seed. Each seed size class was grown in weedy and weed‐free conditions at Kinston, NC during 2007 and 2008 and at Plymouth, NC during 2008. Redroot pigweed (Amaranthus retroflexus L.) overseeding was done to create uniform weed densities. Increasing soybean seed size resulted in greater soybean canopy coverage with the greatest effect at 3 weeks after emergence (WAE) (P < 0.001, P = 0.003, and P < 0.001 at Kinston 2007, Kinston 2008, and Plymouth 2008, respectively) compared with 5 WAE (P = 0.02, P = 0.07, and P = 0.02 at Kinston 2007, Kinston 2008, and Plymouth 2008, respectively). Plants from larger seed sizes had more soybean biomass in all sites when grown with weeds, but in only two sites under weed‐free conditions. Larger seed size improved soybean competitiveness by increasing petiole length and plant height. In the two sites with higher weed population densities, planting larger soybean seed reduced weed biomass at 7 WAE. Results suggest that use of larger planting seed may improve weed control in organic soybean production.}, number={1}, journal={AGRONOMY JOURNAL}, publisher={American Society of Agronomy}, author={Place, G. T. and Reberg-Horton, S. C. and Carter, T. E., Jr. and Smith, A. N.}, year={2011}, pages={175–181} }
 @article{place_reberg-horton_dickey_carter_2011, title={Identifying Soybean Traits of Interest for Weed Competition}, volume={51}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2010.11.0654}, abstractNote={ABSTRACTOrganic soybean [Glycine Max (L.) Merr.] producers rely on a variety of tactics for weed management. The use of soybean cultivars with enhanced ability to compete with weeds may increase weed control. Our objective was to identify genetic traits that may enhance soybean's competitive ability to suppress weeds. Experimental design was a split‐split plot with sets of contrasting soybean genotypes assigned to the main plots, individual genotypes assigned to subplots, and weedy and weed‐free sub‐subplots stripped across blocks for side by side comparison of treatments in weedy and weed‐free conditions. Differences in weed biomass were detected among genotypes in both years at 7 wk after emergence. Narrow‐leaflet small‐seeded natto types were generally poor competitors with weeds. Cultivars released as forage types did not have a consistent advantage over the control. Larger‐seeded tofu genotypes were also variable in weed suppressive ability. However, N04‐8906, the genotype with the greatest 100‐seed weight in this study (24 g), stood out as being among the best for weed suppression, soybean biomass accumulation, ground cover at 3 wk, and early season plant height. Optimum models from multiple regression showed seed size to be the most significant trait measured in overall genotype competitive ability in both years. However, seed size effects on ground cover largely dissipated by 5 wk after emergence.}, number={6}, journal={CROP SCIENCE}, publisher={Crop Science Society of America}, author={Place, George T. and Reberg-Horton, S. Chris and Dickey, David A. and Carter, Thomas E., Jr.}, year={2011}, month={Nov}, pages={2642–2654} }
 @article{smith_reberg-horton_place_meijer_arellano_mueller_2011, title={Rolled Rye Mulch for Weed Suppression in Organic No-Tillage Soybeans}, volume={59}, ISSN={["1550-2759"]}, DOI={10.1614/ws-d-10-00112.1}, abstractNote={Rising demand for organic soybeans and high price premiums for organic products have stimulated producer interest in organic soybean production. However, organic soybean producers and those making the transition to organic production cite weed management as their main limitation. Current weed management practices heavily rely on cultivation. Repeated cultivation is expensive and has negative consequences on soil health. Research is needed to improve organic reduced tillage production. Rye cover crop mulches were evaluated for weed suppression abilities and effects on soybean yield. Experiments were planted in 2008 and 2009 at three sites. Rye was planted in the fall of each year and killed at soybean planting with a roller/crimper or flail mower, creating a thick weed-suppressing mulch with potential allelopathic properties. The mulch was augmented with one of three additional weed control tactics: preemergence (PRE) corn gluten meal (CGM), postemergence (POST) clove oil, or postemergence high-residue cultivation. Roll-crimped and flail-mowed treatments had similar weed suppression abilities at most sites. There were no differences between CGM, clove oil, or cultivation at most sites. Sites with rye biomass above 9,000 kg ha−1of dry matter provided weed control that precluded soybean yield loss from competition. In Goldsboro 2008, where rye biomass was 10,854 kg ha−1of dry matter, the soybean yield in the rolled rye treatment was not significantly different from the weed-free treatment, yielding at 2,190 and 2,143 kg ha−1, respectively. Likewise, no difference in soybean yield was found in Plymouth 2008 with a rye biomass of 9,256 kg ha−1and yields of 2,694 kg ha−1and 2,809 kg ha−1in the rolled rye and weed-free treatments, respectively. At low rye biomass levels (4,450 to 6,606 kg ha−1), the rolled rye treatment soybean yield was 628 to 822 kg ha−1less than the weed-free treatment. High rye biomass levels are critical to the success of this production system. However, high rye biomass was, in some cases, also correlated with soybean lodging severe enough to cause concern with this system.}, number={2}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Smith, Adam N. and Reberg-Horton, Chris and Place, George T. and Meijer, Alan D. and Arellano, Consuelo and Mueller, J. Paul}, year={2011}, pages={224–231} }
 @article{place_reberg-horton_carter_brinton_smith_2011, title={Screening Tactics for Identifying Competitive Soybean Genotypes}, volume={42}, ISSN={["0010-3624"]}, DOI={10.1080/00103624.2011.614040}, abstractNote={Weed control is the biggest obstacle for farmers transitioning to organic soybean production. The breeding of competitive cultivars may provide organic soybean producers with another weed-management tactic. Soybean breeders need screening protocols to identify competitive genotypes. In 2007 and 2008, we tested two screening tactics to nondestructively estimate canopy coverage during the critical period for weed competition. Overhead photography at 3 and 5 weeks after emergence and light interception measurements at 4 and 6 weeks after emergence were compared in their ability to predict soybean and weed biomass at the end of the critical period for weed competition. Photographic digital image processing techniques were compared. Overhead photography at 5 weeks after emergence was most effective at predicting weed-free soybean biomass but overhead photography at 3 weeks after emergence was best able to predict weed biomass associated with soybean genotypes at the end of the critical period for weed competition.}, number={21}, journal={COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS}, publisher={Informa UK Limited}, author={Place, G. T. and Reberg-Horton, S. C. and Carter, T. E. and Brinton, S. R. and Smith, A. N.}, year={2011}, pages={2654–2665} }
 @article{reberg-horton_grossman_kornecki_meijer_price_place_webster_2012, title={Utilizing cover crop mulches to reduce tillage in organic systems in the southeastern USA}, volume={27}, ISSN={["1742-1713"]}, DOI={10.1017/s1742170511000469}, abstractNote={AbstractOrganic systems in the southeastern USA offer unique challenges and solutions to crop production due to regional soil and climate characterized by highly weathered soil types, high precipitation and the capacity to grow cover crops in the winter. Recently, the interest of producers and researchers in high-residue cover crops and conservation tillage systems has increased. Various designs of the roller–crimper to manage cover crops have been invented and demonstrated to growers in the southeastern region of the USA over the past 17 years. The impacts of high-residue cover crop mulches on the agronomic systems in the region are diverse. Legume cover crops assist with meeting N demand from cash crops though they decompose rapidly and are seldom sufficient for N demanding crops such as corn. Cereal cover crop mulches can have the opposite effect by immobilizing N and have a longer impact on soil moisture and weed dynamics. While undesirable for many crops, N immobilization is one possible mechanism for weed suppression in legume cash crops planted into cereal residues. Other cover crop weed suppression mechanisms include physical impedance, light availability, allelopathy and microclimate effects. Regardless of the cause, successful weed control by mulches is highly dependent on having substantial biomass. The southeastern region is capable of producing cover crop biomass in excess of 9000 kg ha−1, which is sufficient for weed control in many cash crops, although supplementary weed control is sometimes necessary. Long-term data are needed to predict when farmers should add supplementary weed control. More work is also needed on how much additional N is required for the cash crops and how best to deliver that N in a high-residue environment using organic sources.}, number={1}, journal={RENEWABLE AGRICULTURE AND FOOD SYSTEMS}, publisher={Cambridge University Press (CUP)}, author={Reberg-Horton, S. Chris and Grossman, Julie M. and Kornecki, Ted S. and Meijer, Alan D. and Price, Andrew J. and Place, George T. and Webster, Theodore M.}, year={2012}, month={Mar}, pages={41–48} }
 @article{place_reberg-horton_jordan_2010, title={Interaction of Cultivar, Planting Pattern, and Weed Management Tactics in Peanut}, volume={58}, ISSN={["1550-2759"]}, DOI={10.1614/ws-d-10-00012.1}, abstractNote={Planting peanut in narrow rows for weed control has not been investigated in recently released Virginia market peanut cultivars. Research was conducted in North Carolina from 2007 to 2009 to determine the effect of cultivar, planting pattern, and level of weed management inputs on weed control, peanut yield, and estimated economic return. Experiments consisted of three levels of weed management (clethodim applied POST, cultivation and hand-removal of weeds, and clethodim and appropriate broadleaf herbicides applied POST), three levels of planting pattern (single rows spaced 91 cm apart, standard twin rows spaced 20 cm apart on 91-cm centers, and narrow twin rows consisting of twin rows spaced 20 cm apart on 46-cm centers), and two Virginia cultivars (‘NC 12C’ and ‘VA 98R’). Weed management affected common lambsquarters, common ragweed, eclipta, nodding spurge, pitted morningglory, Texas millet, and yellow nutsedge control, irrespective of cultivar or planting pattern. Cultivar and planting pattern had only minor effects on weed control and interactions of these treatment factors seldom occurred. Weed control achieved with cultivation plus hand-removal was similar to weed management observed with grass and broadleaf herbicide programs. Pod yield did not differ among treatments when broadleaf weeds were the dominant species but did differ when Texas millet was the most prevalent weed. The highest yield with conventional herbicide weed management was in standard twin and narrow twin row planting patterns, although no differences among planting patterns were noted when cultivation and hand-removal were the primary weed management tactics. Differences in estimated economic return were associated with weed species, and interactions of treatment factors varied by year for that parameter.}, number={4}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Place, G. T. and Reberg-Horton, S. C. and Jordan, D. L.}, year={2010}, pages={442–448} }
 @article{place_reberg-horton_burton_2009, title={Effects of Preplant and Postplant Rotary Hoe Use on Weed Control, Soybean Pod Position, and Soybean Yield}, volume={57}, ISSN={["1550-2759"]}, DOI={10.1614/WS-08-132.1}, abstractNote={Demand for organic food products has consistently increased for more than 20 yr. The largest obstacle to organic soybean production in the southeastern United States is weed management. Current organic soybean production relies on mechanical weed control, including multiple postplant rotary hoe uses. Although postplant rotary hoe use is effective at the weed germination stage, its efficacy is severely compromised by delays due to weather. Preplant rotary hoeing is also a practice that has been utilized for weed control but the effectiveness of this practice to reduce the need for multiple postplant rotary hoeing for organic soybean production in the southeastern United States has not been investigated. Preplant rotary hoe treatments included a weekly rotary hoeing 4 wk before planting, 2 wk before planting, and none. Postplant rotary hoe treatments consisted of zero, one, two, three, and four postplant rotary hoe uses. Weed control was increased with preplant rotary hoeing at Plymouth in 2006 and 2007 but this effect disappeared with the first postplant rotary hoeing. Multiple postplant rotary hoe uses decreased soybean plant populations, decreased soybean canopy height, lowered soybean pod position, and decreased soybean yield. Plant mapping revealed that the percentage of total nodes and pods below 30 cm was increased by increased frequency of postplant rotary hoe use.}, number={3}, journal={WEED SCIENCE}, publisher={Cambridge University Press (CUP)}, author={Place, George T. and Reberg-Horton, S. Chris and Burton, Michael G.}, year={2009}, pages={290–295} }
 @article{place_reberg-horton_dunphy_smith_2009, title={Seeding Rate Effects on Weed Control and Yield For Organic Soybean Production}, volume={23}, ISSN={["1550-2740"]}, DOI={10.1614/WT-08-134.1}, abstractNote={The organic grain sector is one of the fastest growing sectors of the organic market, but farmers in the mid-Atlantic cannot meet the organic grain demand, including the demand for organic soybean. Weed management is cited by farmers as the largest challenge to organic soybean production. Recent soybean population studies show that lower seeding rates for genetically modified organism soybean farmers provide maximum economic return due to high seed technology fees and inexpensive herbicides. Such economic analysis may not be appropriate for organic soybean producers due to the absence of seed technology fees, stronger weed pressures, and price premiums for organic soybean. Soybean seeding rates in North Carolina have traditionally been suggested at approximately 247,000 live seeds/ha, depending on planting conditions. Higher seeding rates may result in a more competitive soybean population and better economic returns for organic soybean producers. Experiments were conducted in 2006 and 2007 to investigate seeding rates of 185,000, 309,000, 432,000, and 556,000 live seeds/ha. All rates were planted on 76-cm row spacing in organic and conventional weed management systems. Increased soybean seeding rates reduced weed ratings at three of the five sites. Increased soybean seeding rates also resulted in higher yield at three of the four sites. Maximum economic returns for organic treatments were achieved with the highest seeding rate in all sites. Results suggest that seeding rates as high as 556,000 live seeds/ha may provide organic soybean producers with better weed control, higher yield, and increased profits.}, number={4}, journal={WEED TECHNOLOGY}, publisher={Cambridge University Press (CUP)}, author={Place, George T. and Reberg-Horton, Samuel Chris and Dunphy, Jim E. and Smith, Adam N.}, year={2009}, pages={497–502} }
 @article{place_bowman_burton_rutty_2008, title={Root penetration through a high bulk density soil layer: differential response of a crop and weed species}, volume={307}, ISSN={["1573-5036"]}, DOI={10.1007/s11104-008-9594-4}, number={1-2}, journal={PLANT AND SOIL}, author={Place, George and Bowman, Daniel and Burton, Michael and Rutty, Thomas}, year={2008}, month={Jun}, pages={179–190} }