Modern legumes are engineered to enhance nutrient allocation to grains and maximize harvest index (HI) and yield. Breeding legumes for cover crop requires optimizing source‐sink relationship to prolong nutrient allocation to vegetative organs, support post‐flowering nodule activity, and extend biological nitrogen fixation (BNF). We studied the variation of faba bean (Vicia faba) germplasm for biomass (DM) and nitrogen (N) allocation to plant organs at the lower and upper parts of the canopy. Three genotypes were established during the 2019 and 2020 growing seasons, and DM, N, and δ15N of upper and lower leaves, stems, pods, seeds, and pod shells were quantified at vegetative, first‐pod, and full‐pod stages. Of the three genotypes, PI 678631 displayed early vigor, allocated more DM and N in vegetative organs, and accumulated more total DM and N than Windsor and PI 655333 by first‐pod stage. The advantage of PI 678631 over the other two genotypes seemed to be associated with smaller allocation of DM and N in pods at early reproductive phase. These findings support existing variations within faba bean germplasm that can be used to improve its ecosystem service as cover crop. Within‐plant variation of δ15N was minimal, suggesting that under favorable soil N and moisture where N remobilization is low, vegetative organs can serve as proxies to estimate the entire plant %Ndfa (proportion of plant N derived from the atmosphere) prior to plant maturity. The δ15N of plant organs at vegetative and early‐pod stages were similar and consistent with the only whole plant δ15N measurement in 2020.

中文翻译：

---

开发豆类覆盖作物品种的步骤：不同生长阶段蚕豆的生物量和氮分配以及株内 δ115N 变化的研究

现代豆类经过精心设计，可增强谷物的养分分配，并最大限度地提高收获指数 (HI) 和产量。育种豆类覆盖作物需要优化源库关系，以延长营养器官的养分分配，支持花后根瘤活性，并延长生物固氮（BNF）。我们研究了蚕豆的变异（蚕豆）种质，用于将生物量（DM）和氮（N）分配给冠层下部和上部的植物器官。2019年和2020年生长季建立了三种基因型，DM、N和δ15在营养期、初荚期和全荚期对上下叶、茎、豆荚、种子和豆荚壳的氮进行定量。三种基因型中，PI 678631表现出较早的活力，在营养器官中分配更多的DM和N，并且在第一荚期比Windsor和PI 655333积累更多的DM和N总量。PI 678631 相对于其他两种基因型的优势似乎与早期繁殖阶段豆荚中较少的 DM 和 N 分配有关。这些发现支持蚕豆种质内现有的变异，可用于改善其作为覆盖作物的生态系统服务。δ 的植物内变化15氮含量极小，这表明在氮再利用较低的有利土壤氮和湿度下，营养器官可以作为代理来估计植物成熟前整个植物的％Ndfa（来自大气的植物氮的比例）。δ15营养期和早期结荚期植物器官的N相似且与唯一的全株δ一致152020 年氮测量。