Including winter legumes during fallow periods in crop rotations may add nitrogen (N) to the agroecosystem through biological N fixation (BNF). This gain will depend on management practices and whether the crop is planted for grain production or as a cover crop. Despite many studies quantified the partial N balance of different legume crops, very few considered the contribution of BNF from belowground structures, which is necessary for more accurate estimations. To estimate biomass, N uptake, and BNF in field-grown field pea and vetch, and study the impact of including belowground structures in the partial N balance of both crops. A two-year field study evaluating two genotypes of field pea (semi-leafless and conventional-leaved) and vetch was performed under field conditions in the Pampean Region (Argentina). Above and belowground biomass (measured in field monoliths to 0.3 m depth), N uptake and N abundance were quantified for determining BNF, and the partial N balance. The partial N balance of field pea as grain crop was negative in most cases (average −7 kg N ha), but, was positive when vetch was evaluated as cover crop (average 51 kg N ha). Including belowground components, BNF improved the partial N balance by 1 and 6 kg N ha in field pea and vetch, respectively. In field pea, the proportion of N uptake derived from BNF (%Ndfa) averaged 43 %, and was not affected by genotype or year, whereas for vetch represented 40 and 18 % of total N uptake in 2018 and 2019, respectively. In field pea, belowground BNF averaged 1.2 kg N ha, and represented 0.9 % of the total N uptake at maturity. In vetch, belowground BNF averaged 6.3 kg N ha and accounted for 3.8 % of total N uptake at full bloom. Biomass and the proportion of N derived from BNF were not affected by the different genotypes in field pea, while in vetch, the environmental conditions that increased %Ndfa were more important than those that affected biomass production for increasing the partial N balance. Although field pea as a grain crop did not provide a consistent N input to the agrosystem, it arises as a convenient crop in terms of N balance compared to other cash crops. Vetch stands as an attractive cover crop, contributing 46–57 kg N ha and 6–9.5 Mg ha of residues to the agrosystem.

中文翻译：

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豌豆和野豌豆的生物固氮：地上和地下结构对部分氮平衡的贡献


在轮作休耕期间种植冬季豆科植物可以通过生物固氮（BNF）向农业生态系统添加氮（N）。这一收益将取决于管理实践以及该作物是用于粮食生产还是作为覆盖作物种植。尽管许多研究量化了不同豆科作物的部分氮平衡，但很少考虑地下结构的 BNF 贡献，而这对于更准确的估计是必要的。估算田间种植的豌豆和野豌豆的生物量、氮吸收量和 BNF，并研究地下结构对两种作物部分氮平衡的影响。在潘皮亚地区（阿根廷）的田间条件下进行了一项为期两年的田间研究，评估了豌豆（半无叶和常规有叶）和野豌豆的两种基因型。对地上和地下生物量（在田间巨石中测量至 0.3 m 深）、氮吸收和氮丰度进行量化，以确定 BNF 和部分氮平衡。在大多数情况下，作为粮食作物的豌豆的部分氮平衡为负（平均-7千克氮·公顷），但当野豌豆被评估为覆盖作物时，部分氮平衡为正（平均51千克氮·公顷）。包括地下成分在内，BNF 使豌豆和野豌豆的部分氮平衡分别提高了 1 公斤和 6 公斤氮公顷。在豌豆中，来自 BNF (%Ndfa) 的氮吸收比例平均为 43%，并且不受基因型或年份的影响，而野豌豆在 2018 年和 2019 年分别占总氮吸收量的 40% 和 18%。在豌豆中，地下 BNF 平均为 1.2 kg N ha，占成熟期总氮吸收量的 0.9%。在野豌豆中，地下 BNF 平均为 6.3 kg N ha，占盛花期总氮吸收量的 3.8%。 豌豆的生物量和来自BNF的氮的比例不受不同基因型的影响，而在野豌豆中，增加%Ndfa的环境条件比影响生物量生产的环境条件对于增加部分氮平衡更重要。尽管豌豆作为粮食作物不能为农业系统提供持续的氮输入，但与其他经济作物相比，它在氮平衡方面是一种方便的作物。野豌豆是一种有吸引力的覆盖作物，可为农业系统贡献 46-57 千克氮/公顷和 6-9.5 毫克/公顷残留物。