Cover crop residue can act as a mulch that will suppress weeds, but as the residue degrades, weed suppression diminishes. Biomass of cover crop residue is positively correlated to weed suppression, but little research is available regarding the composition of cover crop residue and its effect on weed suppression. Field experiments were conducted to determine the impact of cover crop residue properties (i.e., total carbon, total nitrogen, lignin, cellulose, and hemicellulose) on summer annual weed suppression and cash crop yield. Cover crop monocultures and mixtures were planted in the fall and designed to provide a range of biomass and residue properties. Cover crops were followed by corn (Zea mays L.) or soybean [Glycine max (L.) Merr.]. At termination, cover crop biomass and residue components were determined. Biomass ranged from 3,640 to 8,750 kg ha−1, and the carbon-to-nitrogen (C:N) ratio ranged from 12:1 to 36:1. As both cover crop biomass and C:N ratio increased, weed suppression and duration of suppression increased. For example, a C:N ratio of 9:1 is needed to suppress redroot pigweed (Amaranthus retroflexus L.) 50% at 4 wk after termination (WAT), and that increases to 16:1 and 20:1 to have 50% suppression at 6 and 8 WAT, respectively. Similarly, with biomass, 2,800 kg ha−1 is needed for 50% A. retroflexus suppression at 4 WAT, which increases to 5,280 kg ha−1 and 6,610 kg ha−1 needed for 50% suppression at 6 and 8 WAT, respectively. In general, similar trends were observed for pitted morningglory (Ipomoea lacunosa L.) and large crabgrass [Digitaria sanguinalis (L.) Scop.]. Corn and soybean yield increased as both cover crop biomass and C:N ratio increased where no weed control measures were implemented beyond cover crop. The same trend was observed with cash crop yield in the weed-free subblocks, with one exception. This research indicates that cover crop residue composition is important for weed control in addition to biomass.

中文翻译：

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覆盖作物残留成分及其对玉米和大豆夏季一年生杂草抑制的影响

覆盖作物残留物可以作为抑制杂草的覆盖物，但随着残留物的降解，杂草抑制作用会减弱。覆盖作物秸秆生物量与杂草抑制呈正相关，但关于覆盖作物秸秆的组成及其对杂草抑制作用的研究很少。进行了田间试验以确定覆盖作物残留物特性（即总碳、总氮、木质素、纤维素和半纤维素）对夏季年度杂草抑制和经济作物产量的影响。覆盖作物单一栽培和混合物在秋季种植，旨在提供一系列生物量和残留物特性。覆盖作物之后是玉米（玉米L.) 或大豆 [甘氨酸最大 (L.) Merr.]。在终止时，测定覆盖作物生物量和残留物成分。生物质从 3,640 到 8,750 公斤公顷不等-1, 碳氮 (C:N) 比在 12:1 到 36:1 之间。随着覆盖作物生物量和C:N比的增加，杂草抑制和抑制持续时间增加。例如，需要 9:1 的 C:N 比来抑制红根藜（苋菜L.) 终止后 4 周 (WAT) 为 50%，并且分别增加到 16:1 和 20:1，分别在 6 和 8 WAT 时有 50% 的抑制。同样，使用生物质，2,800 kg ha-1需要 50%A. 反曲抑制 4 WAT，增加到 5,280 kg ha-1和 6,610 公斤公顷-1在 6 WAT 和 8 WAT 分别需要 50% 的抑制。一般来说，有坑的牵牛花也观察到了类似的趋势（番薯L.) 和大马唐 [血楹（L.）范围。]。玉米和大豆产量随着覆盖作物生物量和 C:N 比的增加而增加，而在覆盖作物之外没有实施杂草控制措施。在无杂草区的经济作物产量中也观察到了同样的趋势，但有一个例外。该研究表明，除生物量外，覆盖作物残茬成分对于杂草控制也很重要。