Straw incorporation increases crop yield and soil organic carbon sequestration but varies under different natural conditions and farming practices in China: a system analysis

摘要

Lossof soil organic carbon (SOC) from agricultural soils is a key indicator ofsoil degradation associated with reductions in net primary productivity incrop production systems worldwide. Technically simple and locally appropriatesolutions are required for farmers to increase SOC and to improve croplandmanagement. In the last 30 years, straw incorporation (SI) has gradually beenimplemented across China in the context of agricultural intensification andrural livelihood improvement. A meta-analysis of data published before theend of 2016 was undertaken to investigate the effects of SI on cropproduction and SOC sequestration. The results of 68 experimental studiesthroughout China in different edaphic conditions, climate regions and farmingregimes were analyzed. Compared with straw removal (SR), SI significantlysequestered SOC (0–20 cm depth) at the rate of 0.35 (95 % CI,0.31–0.40) Mg C ha−1 yr−1, increased crop grain yield by13.4 % (9.3–18.4 %) and had a conversion efficiency of theincorporated straw C of 16 % ± 2 % across China. The combinedSI at the rate of 3 Mg C ha−1 yr−1 with mineral fertilizer of200–400 kg N ha−1 yr−1 was demonstrated to be the best farmingpractice, where crop yield increased by 32.7 % (17.9–56.4 %) and SOCsequestrated by the rate of 0.85 (0.54–1.15) Mg C ha−1 yr−1.SI achieved a higher SOC sequestration rate and crop yieldincrement when applied to clay soils under high cropping intensities, and inareas such as northeast China where the soil is being degraded. The SOCresponses were highest in the initial starting phase of SI, then subsequentlydeclined and finally became negligible after 28–62 years. However, crop yieldresponses were initially low and then increased, reaching their highest levelat 11–15 years after SI. Overall, our study confirmed that SI created apositive feedback loop of SOC enhancement together with increased cropproduction, and this is of great practical importance to straw management asagriculture intensifies both in China and other regions with differentclimate conditions.