Abstract Diversified grain crop rotations have shown yield advantages, but it is unclear if this is related to improved N supply. Crop residue-N supply could be an important driver of differences observed in contrasting crop rotations. To address this, we focused on a long-term field trial near Guelph Ontario that compares different grain crop rotations and tillage practices. We hypothesized that diversified crop rotations increase the transfer of residue-derived N to subsequent crops. From 2017 to 2018, we used a 15N technique to measure N turnover in a simple corn and soybean rotation compared to a diversified rotation where winter wheat and red clover were included. Although crop yields were greater in the diverse vs. simple rotation, the long-term rotation had no impact on crop residue N turnover to the subsequent crop—a finding that did not support our hypothesis. The recovery of above- plus below-ground residual-N by the subsequent crops varied by crop type and sequence: 9.7–13.5% of corn residue-N was recovered in the soybean seed, 26 % of soybean residue-N was recovered in the corn grain, and 30 % of winter wheat/red clover residue-N was recovered in the corn grain. Below-ground residue-N recoveries in subsequent grain or seed were 4- to 10-times greater than above-ground residues; in terms of the total contribution, below-ground residue-N supplied 8- to 18-times more N than above-ground residues. Indigenous soil N or fixed N were principal contributors to crop N uptake; more so than the crop residues or fertilizer combined. At this site, an accumulated legacy of N fertilizer applications is likely responsible for building a soil N reservoir for crop production, explaining yield benefits observed by diversifying the rotation—but also masking any effect that diversification may have on residue-N turnover and subsequent crop N uptake. To improve N use efficiency, diversifying crop rotations should be accompanied with reduced N fertilizer applications, and better account for below-ground residual N pools as well as legume N inputs.

中文翻译：

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将作物残留物氮追踪到后续作物中：从多样性不同的长期作物轮作中获得洞察

摘要 多样化的粮食轮作显示出产量优势，但尚不清楚这是否与改善氮供应有关。作物残留氮供应可能是在对比作物轮作中观察到的差异的重要驱动因素。为了解决这个问题，我们专注于安大略省圭尔夫附近的一项长期田间试验，该试验比较了不同的粮食作物轮作和耕作方法。我们假设多样化的作物轮作增加了残留物氮向后续作物的转移。从 2017 年到 2018 年，我们使用 15N 技术测量了简单玉米和大豆轮作与包括冬小麦和红三叶草的多样化轮作相比的氮周转量。尽管不同轮作与简单轮作相比，作物产量更高，长期轮作对作物残茬氮向后续作物的转化没有影响——这一发现不支持我们的假设。后续作物对地上和地下残留氮的回收率因作物类型和序列而异：大豆种子中回收了 9.7-13.5% 的玉米残留氮，大豆种子中回收了 26% 的大豆残留氮。玉米粒，玉米粒中回收了 30% 的冬小麦/红三叶草残渣-N。后续谷物或种子中的地下残留氮回收率是地上残留的 4 到 10 倍；就总贡献而言，地下残留物 N 提供的 N 比地上残留物多 8 到 18 倍。本地土壤氮或固定氮是作物吸收氮的主要贡献者；比作物残留物或肥料的总和还要多。在这个网站上，施用氮肥的累积遗产可能负责建立用于作物生产的土壤氮库，解释了通过多样化轮作观察到的产量效益——但也掩盖了多样化可能对残留氮周转和随后的作物氮吸收产生的任何影响。为了提高氮的利用效率，轮作多样化应伴随着减少施氮肥的使用，并更好地考虑地下残留氮库和豆科植物的氮投入。