Department of Agronomy, Kansas State University, 2004 Throckmorton Plant Science Center, Manhattan, Kansas, 66506, USA.
South Australian Research and Development Institute, Adelaide, Australia.
Sci Rep. 2018 Nov 30;8(1):17502. doi: 10.1038/s41598-018-35672-1.
Legumes rely on soil mineral nitrogen (N) and biological N fixation (BNF). The interplay between these two sources is biologically interesting and agronomically relevant as the crop can accommodate the cost of BNF by five non-mutually exclusive mechanisms, whereby BNF: reduces shoot growth and seed yield, or maintains shoot growth and seed yield by enhanced photosynthesis, or reduced root:shoot ratio, or maintains shoot growth but reduces seed yield by reducing the fraction of shoot biomass allocated to seed (harvest index), or reducing concentration of oil and protein in seed. We explore the impact of N application on the seasonal dynamics of BNF, and its consequences for seed yield with emphasis on growth and shoot allocation mechanisms. Trials were established in 23 locations across the US Midwest under four N conditions. Fertilizer reduced the peak of BNF up to 16% in applications at the full flowering stage. Seed yield declined 13 kg ha per % increase in RAU. Harvest index accounted for the decline in seed yield with increasing BNF. This indicates the cost of BNF was met by a relative change in dry matter allocation against the energetically rich seed, and in favor of energetically cheaper vegetative tissue.
豆类植物依赖于土壤矿物氮（N）和生物固氮（BNF）。这两种来源之间的相互作用在生物学上很有趣，在农业上也很重要，因为作物可以通过五种非互斥的机制来承担 BNF 的成本，即 BNF：减少地上部分的生长和种子产量，或通过增强光合作用维持地上部分的生长和种子产量，或减少根冠比，或维持地上部分的生长但通过减少分配给种子的地上部分生物量（收获指数）来降低种子产量，或降低种子中油和蛋白质的浓度。我们探讨了氮素应用对 BNF 季节性动态及其对种子产量的影响，重点研究了生长和地上部分分配机制。在北美中西部的 23 个地点进行了四项氮素条件的试验。在盛花期进行施肥处理，可使 BNF 的峰值降低多达 16%。每增加 1%的 RAU，种子产量就会下降 13 公斤/公顷。收获指数解释了随着 BNF 的增加而导致的种子产量下降。这表明 BNF 的成本是通过相对改变干物质分配来应对富含能量的种子，转而支持能量较低的营养组织来承担的。
