ABSTRACT

Crop models can help in identifying constraints to crop production and enhancing crop yield. Because one of the major constraints is the availability of nitrogen for seed production, evaluation of nitrogen accumulation is important for soybean crop models. In the present study, we developed a soybean crop model to evaluate biomass production and nitrogen accumulation of Japanese soybean cultivars grown in upland fields converted from paddy fields. The model simplified the effects of leaf nitrogen deficit on biomass production by reducing only the leaf area while maintaining leaf nitrogen concentration, and we introduced a zero-order reaction kinetics model to estimate soil nitrogen supply. The proposed model was observed to simulate the accumulation of aboveground biomass and nitrogen content in both nodulating and non-nodulating soybean cultivars until the mid-seed filling period. The model accounts for 94% of the observed variations in aboveground biomass and nitrogen content and for 69% of the observed variation in seed biomass. The normalized root mean square errors of aboveground biomass, nitrogen content, and seed biomass are 19.3%, 19.6%, and 20.2%, respectively. Because the model does not include the effects of soil water status on pod formation and nitrogen fixation, seed biomass was overestimated in some cases. However, our model quantified the effects of changes in the soil nitrogen supply and biological nitrogen fixation on soybean production and will be useful for identifying and eliminating production constraints in Japanese soybeans.

摘要

作物模型有助于确定作物生产的制约因素并提高作物产量。由于主要限制因素之一是种子生产中氮的可用性，因此氮积累的评估对于大豆作物模型很重要。在本研究中，我们开发了一种大豆作物模型，以评估在由稻田转变的旱田中种植的日本大豆品种的生物量生产和氮积累。该模型通过仅减少叶面积同时保持叶氮浓度来简化叶氮缺乏对生物量生产的影响，我们引入了零级反应动力学模型来估计土壤氮供应。观察到所提出的模型模拟了结瘤和非结瘤大豆品种在种子灌浆中期之前的地上生物量和氮含量的积累。该模型解释了 94% 的地上生物量和氮含量观察到的变化，以及 69% 的观察到的种子生物量变化。地上生物量、氮含量和种子生物量的归一化均方根误差分别为 19.3%、19.6% 和 20.2%。由于该模型不包括土壤水分状况对豆荚形成和固氮的影响，因此在某些情况下高估了种子生物量。然而，