Soil acidity can impair biological N₂ fixation (BNF) and increase soybean (Glycine max L.) reliance on soil N to satisfy its plant N demand. This study aimed to evaluate the effect of liming, fertilization strategy, and grazing on: i) the N supplied via BNF process, ii) partial N-balance, and iii) soybean yield, in an integrated crop-livestock system under a non-tilled sandy and acidic Acrisol. Initial soil conditions were soil pH of 4.0 and Al saturation of 50%. Limestone was applied to rise soil pH to 6.0 and a control area was kept with the initial soil conditions. Soybean was grown in the summer and Italian ryegrass (as a cover crop or grazed by sheep) in the winter. Fertilization strategies consisted in applying P and K prior to soybean or ryegrass. Partial N-balance was calculated by the difference between N derived from BNF and N removed in soybean seeds. Contribution of N from the atmosphere to soybeans was on average 62 and 66% in plots without and with liming, respectively. The fixed-N was 27% greater under low soil acidity due to lime. Partial N-balance was positive in both treatments, but 57% greater in the limed- relative to the non-limed (+58 kg ha⁻¹) soils, resulting in 11% soybean yield increase when lime was added. The most relevant soil chemical properties influencing N fixation were soil pH and Al saturation. Grazing and fertilization strategies had no effect on soil acidity properties, N supply, and soybean evaluations. Further research should explore the long-term effect of grazing, fertilization strategies, and liming.

土壤酸度会损害生物N ₂固定（BNF），并增加大豆（Glycine max L.）对土壤N的依赖，以满足其植物N的需求。这项研究的目的是评估石灰，施肥策略的效果，放牧：i）第N提供通过BNF处理，ii）部分氮素平衡，iii）大豆产量，在非倾斜的含沙酸性酸性Acrisol作物-畜牧综合系统中进行。初始土壤条件是土壤pH值为4.0，铝饱和度为50％。施用石灰石将土壤pH值升高至6.0，并在初始土壤条件下保持对照区域。夏季种植大豆，冬季种植意大利黑麦草（作为农作物或被绵羊放牧）。施肥策略包括在大豆或黑麦草之前施用磷和钾。通过从BNF衍生出的氮与大豆种子中去除的氮之间的差异计算部分N平衡。在没有和有石灰的地块上，来自大气的氮对大豆的平均贡献分别为62％和66％。在低土壤酸度下，由于石灰，固定氮增加了27％。两种治疗均使部分N平衡为阳性，^-1）的土壤，添加石灰可使大豆单产提高11％。影响固氮最相关的土壤化学性质是土壤的pH值和铝饱和度。放牧和施肥策略对土壤酸度，氮素供应和大豆评估没有影响。进一步的研究应探索放牧，施肥策略和石灰的长期影响。