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.

中文翻译：

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塞拉多免耕系统中覆盖作物和土壤有机质库的化学成分

在免耕系统 (NTS) 中，建议使用覆盖作物来提高农业系统的生产力。此外，NTS 覆盖作物的更大多样性有利于增加土壤碳 (C) 储量。然而，关于覆盖作物的化学成分与 SOM 不稳定和稳定部分的积累之间关系的已发表数据很少。我们评估了覆盖作物的化学成分与 SOM 组分、碳库和玉米产量之间的关系。测定了玉米淡季栽培的Urochloa ruziziensis、Canavalia brasiliensis、Cajanus cajan和Sorghum bicolor的半纤维素、纤维素和木质素含量。巴西卡纳瓦利亚具有高 N（20.96 g kg ^-1）和半纤维素（185.67 g kg ^-1）含量，较低的木质素含量（39.50 g kg ^-1）和高干物质产量（3,251 kg ha ^-1）。所有这些特性导致了更好的 SOM 质量。Urochloa ruziziensis具有较高的半纤维素和较低的木质素含量以及较低的木质素/N 比，与 TOC 的积累有关（在 0 至 10 厘米和 10 至 20 厘米层中分别为19.95 和 18.33 g kg ^-1 ）和土壤中与矿物质相关的有机碳（平均为 16.68 g kg ^-1）。N：木质素比率低于 2.0 的覆盖植物是土壤固碳的基础。总之，建议采用Urochloa ruziziensis和Canavalia brasiliensis作为覆盖植物改善了 Cerrado 地区的玉米产量、土壤有机质质量和碳封存。