Data from: Barley cover crops outperform brown mustard for early-season weed control in New Mexico chile pepper

Barley (Hordeum vulgare L.) and brown mustard [Brassica juncea (L.) Czern.] are winter cover crops known to produce allelochemicals that suppress plant growth. Incorporating barley or brown mustard residues into the soil before planting a spring-seeded cash crop may suppress early-season weeds in the cash crop; however, the comparative levels of weed suppression offered by barley and brown mustard cover crops incorporated into soil have not been determined. This study analyzed the relative capacities of barley and brown mustard cover crops to suppress early-season weeds of spring-seeded chile pepper (Capsicum annuum L.). Reductions in weed density or hand-hoeing time as a result of barley and/or brown mustard cover crop treatment were determined in two chile pepper fields in New Mexico over two growing seasons. For cover crop species that suppressed weeds in multiple site-years, a controlled environment study clarified possible growth stages adversely affected by determining the effects of cover crop–amended soil on the germination and seedling development of Palmer amaranth (Amaranthus palmeri S. Watson). Field study results indicated barley reduced early-season weed densities of chile pepper by up to 80 % compared with the noncover control. Barley also reduced hoeing time in 3 of 4 site-years without affecting chile pepper fruit yield. Mustard cover crops reduced weed density in only 1 site-year (56 % reduction relative to noncover control) and did not decrease hoeing time. The controlled environment study indicated that soil amended with barley slowed germination of A. palmeri without inhibiting seedling development. The results of this study indicate that a barley cover crop is more effective than brown mustard for early-season weed control of chile pepper in the southwestern United States.大麦（Hordeum vulgare L.）与褐芥[Brassica juncea (L.) Czern.]是两类公认可产生化感物质以抑制植物生长的冬季覆盖作物。在春播经济作物播种前，将大麦或褐芥残体还田，可抑制该经济作物苗期杂草的生长，但目前尚未明确大麦与褐芥覆盖作物还田后所提供的抑草相对效能。本研究针对大麦与褐芥覆盖作物对春播辣椒（Capsicum annuum L.）苗期杂草的抑制能力展开对比分析。试验于新墨西哥州的两块辣椒田、两个生长季中开展，评估了大麦和/或褐芥覆盖作物处理后杂草密度与人工锄草时长的变化情况。针对在多个试验点-季次中表现出抑草效果的覆盖作物，本研究通过受控环境试验，测定覆盖作物改良土壤对帕尔默苋（Amaranthus palmeri S. Watson）的种子萌发与幼苗生长的影响，以明确其可能产生抑制作用的生长阶段。田间试验结果表明，相较于无覆盖对照组，大麦可使辣椒苗期杂草密度降低最高达80%。此外，在4个试验点-季次中的3个里，大麦还能有效减少锄草时长，且未对辣椒果实产量造成负面影响。而褐芥覆盖作物仅在1个试验点-季次中实现了杂草密度的降低（较无覆盖对照组降幅达56%），且未能减少人工锄草时长。受控环境试验结果显示，经大麦改良的土壤可延缓帕尔默苋的种子萌发，但不会抑制其幼苗生长。本研究结果证实，在美国西南部的辣椒苗期杂草防控工作中，大麦覆盖作物的抑草效果优于褐芥覆盖作物。