The individual nitrogen (N) contribution from above-ground plant residue (AGR) and total below-ground residuals (BGR) to a subsequent wheat crop remains poorly explored. The need to understand this dynamic is crucial for optimizing crop yield and soil nutrient management. This study aimed to discern the individual N contributions from AGR and BGR to a succeeding wheat crop and understand the implications of various grain legume residues on these contributions. A four-year field study consisting of two 2-year grain legume–cereal cropping sequences was conducted in Saskatoon, SK, Canada. The grain legumes were chickpea, faba bean, lentil, and field pea, with spring wheat grown as the reference crop in 2014 and 2016. Each plot was split into quadrants with one quadrant receiving N-urea and the other three receiving non-labeled (natural abundance, NA) urea in spring of the pulse phase. After pulse harvest, N-AGR was swapped with NA-AGR when returned to the field, resulting in sub-plots with N-AGR/NA-BGR and NA-AGR/N-BGR combinations. In 2015 and 2017 all plots were planted with spring wheat and were fertilized based on soil mineral N measurements and target yields. One NA quadrant received N-urea during the cereal phase to track the fate of fertilizer N versus legume N. Grain legume residue species did not affect the seed yield of the subsequent wheat crop. However, wheat grown on lentil and pea residue required less N fertilizer than other residues. Over the five tested residues, BGR (roots, rhizodeposits, residual fertilizer, and soil) was the largest N source, accounting for 70–91% of wheat N uptake, which surpassed the combination of the contribution from AGR (1–11% of wheat N uptake) and fertilizer (5–21% of the wheat N uptake). Among BGR components, soil was the main N contributor to subsequent wheat. The N recovery rates for the wheat crop were below 9% for AGR, 18% for BGR, and 26% for fertilizer N. Below-ground residue, particularly the soil, plays a pivotal role in regulating N supply to the succeeding wheat crop, overshadowing contributions from AGR and fertilizer. This research underscores the significance of BGR, especially the soil, in N management for subsequent crops. Recognizing these dynamics can help tailor crop residue management strategies and optimize soil nutrient supply for subsequent crops.

中文翻译：

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量化鹰嘴豆、蚕豆、扁豆、豌豆和小麦的地上和地下残留物对后续小麦作物氮营养的贡献


地上植物残留物 (AGR) 和地下总残留物 (BGR) 对后续小麦作物的单个氮 (N) 贡献仍知之甚少。了解这种动态对于优化作物产量和土壤养分管理至关重要。本研究旨在辨别 AGR 和 BGR 对后续小麦作物的单独氮贡献，并了解各种豆类残留物对这些贡献的影响。在加拿大萨斯卡通进行了一项为期四年的实地研究，包括两个为期两年的豆类-谷物种植序列。谷物豆类包括鹰嘴豆、蚕豆、扁豆和豌豆，并以 2014 年和 2016 年种植的春小麦作为参考作物。每个地块被分成几个象限，其中一个象限接受 N-尿素，其他三个象限接受非标记（自然丰度，NA) 春季脉冲阶段的尿素。豆类收获后，当返回田间时，N-AGR 被替换为 NA-AGR，从而产生具有 N-AGR/NA-BGR 和 NA-AGR/N-BGR 组合的子地块。 2015年和2017年，所有地块都种植了春小麦，并根据土壤矿物质氮测量和目标产量施肥。一个 NA 象限在谷物阶段接受氮尿素，以跟踪化肥氮与豆科作物氮的命运。谷物豆类残留物不会影响后续小麦作物的种子产量。然而，用扁豆和豌豆残渣种植的小麦比其他残渣需要更少的氮肥。在五个测试残留物中，BGR（根、根际沉积物、残留肥料和土壤）是最大的氮源，占小麦氮吸收的70-91%，超过了AGR贡献的总和（1-11%）小麦氮吸收）和肥料（小麦氮吸收的 5-21%）。 在 BGR 组成部分中，土壤是后来小麦的主要氮素贡献者。小麦作物的氮肥回收率，AGR 低于 9%，BGR 低于 18%，肥料 N 低于 26%。地下残留物，特别是土壤，在调节后续小麦作物的氮供应方面发挥着关键作用。掩盖了 AGR 和化肥的贡献。这项研究强调了 BGR（尤其是土壤）在后续作物氮管理中的重要性。认识这些动态可以帮助制定作物残茬管理策略并优化后续作物的土壤养分供应。