@article{wells_reberg-horton_smith_grossman_2013, title={The Reduction of Plant-Available Nitrogen by Cover Crop Mulches and Subsequent Effects on Soybean Performance and Weed Interference}, volume={105}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2012.0396}, abstractNote={A 3 site‐year study was conducted to investigate the impact of roller‐crimped rye (RC) (Secale cereale L.) mulches on soil N immobilization and subsequent effects on weed suppression and soybean [Glycine max (L.) Merr.] yield. Treatments consisted of: (i) RC, (ii) conventional tillage with neither rye cover crop nor weed control measures (WC), (iii) conventional tillage plus herbicide weed control (CT+HB), and, (iv) roller‐crimped rye plus herbicide (RC+HB). The rye biomass varied between the sites with 4400, 8300, and 7084 kg ha−1 dry matter (DM) for Goldsboro 2009, Kinston 2009, and Kinston 2010, respectively. During the season, the flow of soil inorganic N was monitored via ion‐exchange probes and by direct extractions at two depths (0–10 and 10–25 cm) every 2 wk. Tissue data was collected every 2 wk on soybean and redroot pigweed (Amaranthus retroflexus L.) to determine the C/N ratio. For all sites, peak N immobilization occurred between 4 and 6 weeks after planting (WAP), indicated by a reduction in soil inorganic N. Results from the ion‐exchange probes showed similar trends of the extractable soil inorganic N at all sites. Pigweed C/N ratios revealed a growing divergence between the two systems, with a severe N deficiency in the RC. Even with varying rye biomass production across environments the RC system created an extremely low N environment, suggesting that when a cereal cover crop is paired with a legume cash crop, reduced weed crop interference may result, with little reduction in soybean yield.}, number={2}, journal={AGRONOMY JOURNAL}, publisher={American Society of Agronomy}, author={Wells, M. S. and Reberg-Horton, S. C. and Smith, A. N. and Grossman, J. M.}, year={2013}, pages={539–545} }
 @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{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} }