Cropping system characteristics such as tillage intensity, crop identity, crop-livestock integration and the application of off-farm synthetic inputs influence weed abundance, plant community composition and crop-weed competition. The resulting plant community, in turn, has species-specific effects on soil microbial communities which can impact the growth and competitive ability of subsequent plants, completing a plant–soil feedback (PSF) loop. Farming systems that minimize the negative impacts of PSFs on subsequent crop growth can increase the sustainability of the farming enterprise. This study sought to assess the individual and combined impact of the cropping system (certified organic-grazed, certified organic till and conventional no-till) and crop sequence [pairwise rotations with safflower (Carthamus tinctorius), yellow sweet clover (Melilotus officinalis) and winter wheat (Triticum aestivum)] on the PSF magnitude and direction. All cropping systems followed the same 5-year rotation and had completed one full rotation before soil was sampled. In a greenhouse setting, a sterile soil mix was inoculated with field soil collected from all systems and three crops. The PSF study consisted of two stages (conditioning and response phases) that mimicked the rotation stages occurring in the field. PSFs were calculated by comparing the biomass of the response phase plants grown in inoculated and uninoculated soils. The farm management system affected PSFs, inferring that tillage reduction can encourage more positive PSFs. Crop sequence did not affect PSF but interacted strongly with the farm system. As such, the effects of the farming system on PSFs are best illustrated when taken into account with the identity of the previous and current crops of a cropping sequence.

中文翻译：

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农业系统对生物介导的植物-土壤反馈的影响

耕作系统特征，如耕作强度、作物特性、作物-牲畜整合和非农合成投入的应用会影响杂草丰度、植物群落组成和作物-杂草竞争。由此产生的植物群落反过来又会对土壤微生物群落产生特定物种的影响，从而影响后续植物的生长和竞争能力，从而完成植物-土壤反馈 (PSF) 循环。将 PSF 对后续作物生长的负面影响降至最低的农业系统可以提高农业企业的可持续性。本研究旨在评估种植系统（经认证的有机放牧、经认证的有机耕作和传统免耕）和作物顺序[与红花成对轮作（红花）、黄甜三叶草（椴树) 和冬小麦 (小麦)] 关于 PSF 的大小和方向。所有种植系统都遵循相同的 5 年轮作，并在土壤取样前完成了一轮完整的轮作。在温室环境中，用从所有系统和三种作物收集的田间土壤接种无菌土壤混合物。PSF 研究包括两个阶段（调节阶段和响应阶段），模拟现场发生的旋转阶段。通过比较在接种和未接种土壤中生长的响应期植物的生物量来计算 PSF。农场管理系统影响了 PSF，推断减少耕作可以鼓励更积极的 PSF。作物序列不影响 PSF，但与农场系统有强烈的相互作用。因此，