Biological N2 fixation by soybeans grown with or without liming on acid soils in a no-till integrated crop-livestock system

• Published in: Soil & tillage research Vol. 209; p. 104923
• Main Authors: Alves, Lucas Aquino, Ambrosini, Vítor Gabriel, Denardin, Luiz Gustavo de Oliveira, Flores, João Pedro Moro, Martins, Amanda Posselt, Filippi, Dionata, Bremm, Carolina, Carvalho, Paulo César de Faccio, Farias, Gustavo Duarte, Ciampitti, Ignacio A., Tiecher, Tales
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-05-2021
• Subjects: 15N natural abundance; Al saturation; Low pH; N-fixed; Soil acidity; Soil acidity; Al saturation; N-fixed; 15N natural abundance; Low pH
• ISSN: 0167-1987; 1879-3444
• DOI: 10.1016/j.still.2020.104923

•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 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.