Chemical composition of cover crops and soil organic matter pools in no-tillage systems in the Cerrado

In no-tillage systems (NTS), cover crops are recommended to increase the productivity of agricultural systems. Furthermore, a greater diversity of cover crops in NTS favours an increase in soil carbon (C) stocks. However, there are scarce published data on the relationship between the chemical composition of cover crops and the accumulation of labile and stable fractions of SOM. We evaluated the relationship between the chemical composition of cover crops and SOM fractions, C stocks and maize yield. Hemicellulose, cellulose and lignin contents were determined for Urochloa ruziziensis, Canavalia brasiliensis, Cajanus cajan and Sorghum bicolor, cultivated in the off-season of maize. Canavalia brasiliensis had high N (20.96 g kg(-1)) and hemicellulose (185.67 g kg(-1)) contents, lower lignin content (39.50 g kg(-1)) and high dry matter yield (3,251 kg ha(-1)). All these characteristics resulted in a better SOM quality. Urochloa ruziziensis, with higher hemicellulose and lower lignin contents, and low lignin/N ratio, was associated with accumulation of TOC (19.95 and 18.33 g kg(-1) in 0- to 10-cm and 10- to 20-cm layers, respectively) and mineral-associated organic C (on average, 16.68 g kg(-1)) in the soil. Cover plants with N:lignin ratio lower than 2.0 are fundamental for soil C sequestration. In conclusion, it is recommended the adoption of Urochloa ruziziensis and Canavalia brasiliensis as cover plants improve maize production, soil organic matter quality and C sequestration in the Cerrado region.

Automated summary

In no-tillage systems, cover crops play a crucial role in increasing agricultural productivity and soil carbon stocks. The chemical composition of cover crops like Canavalia brasiliensis and Urochloa ruziziensis can significantly impact soil organic matter quality and carbon sequestration, ultimately improving maize production in the Cerrado region.