Sustainability Analysis of Nitrogen Use Efficiency in Soybean-Corn Succession Crops of Midwest Brazil.

Nitrogen (N) is abundant in the atmosphere as N_2, which is converted into reactive forms (Nr) for plant assimilation. In pre-industrial times, atmospheric N₂ conversion to Nr balanced Nr reconversion to N₂, but 20th-century human activity intensified this conversion via synthetic fertilizers, biological N₂ fixation, and fossil fuel burning. The surplus of Nr detrimentally impacts ecosystems and human well-being. This study aimed to assess the N use efficiency in the soil–plant system of the soybean-corn succession ( S P S S , C ) in Mato Grosso and Mato Grosso do Sul, Brazil's midwest. We estimated N macrofluxes in S P S S , C and identified key agro-environmental indicators. Between 2008 and 2020, the yearly sowed area for the S P S S , C increased by 3.3-fold (currently 7.3 million ha). The average annual input of net anthropogenic Nr, average annual N balance, and N loss in S P S S , C was estimated to be ~204 kg [N] ha⁻¹_, 57 kg [N] ha⁻¹, and 30 kg [N] ha⁻¹, respectively, indicating persistent N accumulation and loss. The average results of the agronomic efficiency and N retention indicator in the S P S S , C was 0.71 and 0.90, respectively. Modest N use efficiency results reflect N loss effects. Despite these limitations, there are opportunities in S P S S , C for management strategies to reduce N loss and enhance efficiency. [ABSTRACT FROM AUTHOR]