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• Liming increases the amount of biological nitrogen fixation. • Liming provides higher soybean yields and a more positive N-balance. • Soil pH and Al saturation are key factors in biological nitrogen fixation. Soil acidity can impair biological N 2 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. [ABSTRACT FROM AUTHOR]

• Liming increased gross N mineralization and nitrification during the summer fallow. • No-tillage enhanced the liming effect on gross N mineralization. • N immobilization was higher in traditional tillage. • The gross N transformations and microbial indicators decreased during the summer period. • During the fallow period, NH 4 +, DOC and DON accumulated in all the treatments. In the Mediterranean rainfed agriculture, a summer fallow is necessary because of the severe drought and high temperatures. Due to suppressed plant nitrogen (N) uptake during this period, an accumulation of inorganic N in the soil may occur, which could be lost from the system during the first autumn rains. Both mineralization and nitrification rates can be affected by agricultural practices, such as tillage or liming, influencing the amount of available N present in the soil during the fallow period. In this study, we investigated the effects of two common agricultural practices, no-tillage (instead of traditional tillage) and liming, on soil gross N transformations during the summer fallow. Liming increased gross N mineralization (from 1.21 to 1.78 mg N kg−1 day−1) and gross nitrification (from 0.44 to 0.76 mg N kg−1 day−1) while traditional tillage increased N immobilization. Tillage did not affect gross nitrification but the effect of liming on gross N mineralization was enhanced in no-tillage plots. The total bacteria abundance was enhanced by liming and no-tillage and seemed to be responsible for gross N mineralization and immobilization. The gross mineralization, nitrification and microbial immobilization decreased during the summer fallow with an overall reduction by 40%, 56%, 74% and 54% in gross N mineralization, gross nitrification, ammonium immobilization and nitrate immobilization, respectively. The accumulation of ammonium could be interpreted as a consequence of the decoupling between ammonium production and consumption rates. The increase of gross N mineralization and nitrification caused by liming application could result in augmented risks of N losses via nitrate leaching and gaseous losses in autumn, especially under no-tillage. However further studies are required to elucidate the nitrate fate of the in Mediterranean agricultural soils under those management practices. [ABSTRACT FROM AUTHOR]