Abstract Agroecosystems make up a significant portion of terrestrial ecosystems and receive a disproportionally high amount of terrestrial nitrogen inputs from fertilizer, leading to nitrogen loss and associated environmental problems. Integrated crop livestock systems, such as pasture-integrated crop rotations, may be more environmentally sustainable however the long-term effects of this management practice on soil microorganisms and nitrogen transformations are not well understood. To address this knowledge gap, samples were collected from a long-term experiment designed to assess the impacts of, and interaction between, compost application and pasture-integrated crop rotations. The compost-input and pasture-integrated rotation treatments increased soil organic matter by 41 % and 14 % respectively, carbon mineralization by 127 % and 146 %, and extracellular enzyme activity by 74 % and 35 %, suggesting enhanced heterotrophic microbial activity. Compost addition led to rapid ammonification, increased potential nitrification rates ∼3-fold, and enhanced nitrate concentration by ∼75%. Further, compost addition more than doubled the abundance of prokaryotic ammonia oxidizing organisms (AOO). These effects of compost on nitrogen cycling were greatly mitigated by the pasture-integration likely due to enhanced microbial decomposition activity associated with carbon inputs from perennial grasses. Specifically, pasture-integration mitigated increases in potential nitrification, AOO abundance, and soil nitrate concentrations. The rates of potential nitrification were correlated with the abundance of AOO, highlighting the connection between nitrogen cycling processes and microbial community composition. These patterns in nitrifier abundances, potential nitrification rates, and nitrate levels indicate that the long-term integration of pasture in crop rotations has the potential to reduce early-season nitrogen loss without reducing crop productivity. This work demonstrates how management practices that facilitate favorable interactions between microbial carbon and nitrogen cycling may enhance agroecosystem sustainability and reduce nitrogen pollution.

中文翻译：

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轮作中的牧场影响微生物的生物多样性和功能，降低堆肥造成氮流失的可能性

摘要 农业生态系统构成了陆地生态系统的重要组成部分，从肥料中获得了不成比例的大量陆地氮输入，导致氮流失和相关的环境问题。综合作物畜牧系统，如牧场综合作物轮作，可能在环境上更具可持续性，但这种管理做法对土壤微生物和氮转化的长期影响尚不清楚。为了弥补这一知识差距，我们从一项旨在评估堆肥施用和牧场综合作物轮作的影响和相互作用的长期实验中收集样本。堆肥投入和牧场综合轮作处理分别使土壤有机质增加了 41% 和 14%，碳矿化增加了 127% 和 146%，和细胞外酶活性分别提高了 74% 和 35%，表明异养微生物活性增强。添加堆肥导致快速氨化，增加潜在硝化率约 3 倍，并将硝酸盐浓度提高约 75%。此外，堆肥的添加使原核氨氧化生物 (AOO) 的丰度增加了一倍以上。堆肥对氮循环的这些影响被牧场整合大大减轻，这可能是由于与多年生草的碳输入相关的微生物分解活动增强。具体而言，牧场整合减缓了潜在硝化作用、AOO 丰度和土壤硝酸盐浓度的增加。潜在硝化速率与 AOO 丰度相关，强调氮循环过程与微生物群落组成之间的联系。这些硝化菌丰度、潜在硝化率和硝酸盐水平的模式表明，长期将牧场纳入轮作中，有可能在不降低作物生产力的情况下减少早季氮损失。这项工作展示了促进微生物碳和氮循环之间有利相互作用的管理实践如何可以增强农业生态系统的可持续性并减少氮污染。