Soil organic carbon formation efficiency from straw/stover and manure input and its drivers: Estimates from long‐term data in global croplands

Abstract

Abstract New soil organic carbon (SOC) formation in cropland from straw/stover or manure input is a vital source of SOC for climate change mitigation. However, location and variations in the efficiency, specifically the ratio of new SOC formation to organic C input (NCE), remain unquantified globally. In this study, the spatial variability of cropland NCE from straw/stover or manure input and explanatory factors were determined by analyzing 897 pairs of long‐term field measurements from 404 globally distributed sites and by mapping grid‐level cropland NCEs. The global NCE for paddy and upland averaged 13.8% (8.7%–25.1%, 5th–95th percentile) and 10.9% (6.8%–17.3%), respectively. The initial SOC and the clay content of soil, rather than temperature, were the most important factors regulating NCE. A parabola with an apex at approximately 17 g kg −1 between the initial SOC and NCE was resolved, and a positive correlation between soil clay content and NCE was observed. High‐resolution mapping of the global NCE derived from manure/straw and insight into NCE dynamics provide a benchmark for diagnosing cropland soil C dynamics under climate change and identifying priority regions and actions for C management.