Long-term organic amendments improved soil carbon sequestration to support crop production

Background Currently, soil productivity is severely restricted by the degradation of soil quality in China. Crop straw and livestock manure, as the main by-products in agricultural production, are widely promoted to replace chemical fertilizer and improve soil quality to support agricultural sustainability. Aims We investigated the long-term effects of organic amendments and nitrogen (N) fertilization on soil quality, including the changes in soil organic carbon (SOC) content and soil aggregates distribution, and the dynamics of soil labile organic carbon (C) fractions and soil respiration, and crop yield. Methods A field experiment (started in 2009) with a winter-wheat and summer-maize rotation system was designed with four treatments: without fertilization (CK), with manure (M), with straw (S), and with straw plus N fertilizer (SN). The relevant indicators were measured after 10 years of annual fertilization in 2018. Results Compared to the CK treatment, M, S, and SN significantly enhanced soil organic carbon (SOC) by 190, 67, and 113%, respectively. M and SN, but not S, significantly improved the dynamics of soil labile organic C fractions, soil aggregates distribution, mean weight diameter (MWD), and geometric mean diameter (GMD). Simultaneously, soil respiration of M and SN were significantly increased by 21% and 15% compared to CK. Based on the improvement of soil quality, the wheat and maize yield in a rotation of different treatments were as follows: M (20.33 Mg ha(-1)) > SN (14.09 Mg ha(-1)) > S (6.45 Mg ha(-1)) > CK (4.98 Mg ha(-1)). Conclusion Overall, long-term organic amendments and N fertilization improved soil chemical and physical quality to support high-yielding crop production.