Integrated crop-livestock systems with crop diversification increase soil C and N levels and stocks in subtropical paddy fields in Brazil

Integrated crop-livestock systems (ICLS) promote diversification in agricultural ecosystems; however, few studies address the impact of ICLS on soil carbon (C) and nitrogen (N) contents, especially in paddy fields in subtropical climates. In this context, the objective of this study was to evaluate the effects of different ICLS on soil C and N fractions and stocks. The long-term (eight-year) ICLS field trial under no-tillage, in a Albaqualf, is located in southern Brazil. The treatments are different production systems: S1 – rice monocrop; S2 – manual rice in succession with winter ryegrass; S3 – annual rotation between soybean and rice with winter ryegrass; S4 – rotation between rice, soybean, corn, and Sudangrass in summer, with winter ryegrass and white clover; S5 – Three consecutive years of perennial pasture in summer, followed by one year of rice with ryegrass, white clover, and lotus in winter. With the exception of S1, all systems included pasture during the winter season, with grazing animals present. Soil samples were collected from different layers, and stocks and fractions of total C and N, labile SOM (<53 μm), and non-labile SOM (>53 μm) were evaluated. The results indicated that ICLS systems under high diversity (S4 and S5) favored soil C and N contents and total stocks in all layers evaluated, while S1 presented the lowest values. Labile and non-labile C and N fractions were also positively affected, mainly at the surface (0–0.1 m) under ICLS use. ICLS contribute to increasing soil C and N and the sustainability of rice production systems in subtropical lowlands. Thus, integrated rice cultivation with crop diversity increases, on average, the stocks of labile C, non-labile C and total C at a depth of 0–0.4 m by 30%, 20% and 22%, respectively, compared to rice under monocrop. • ICLS increased labile, non-labile, and total C stocks by 30%, 20%, and 22% at 0–0.4 m vs. rice monoculture. • Integrated crop-livestock systems (ICLS) increase the potential for carbon (C) sequestration. • ICLS constitute a sustainable alternative to rice monoculture in the subtropical regions of Brazil.