Improving cropland soil water management to promote soil organic carbon increase through organic material returning in cold black soil areas

Abstract

Manure returning (OMR) and straw returning (SWR) practices are widely adopted to enhance soil organic carbon (SOC) sequestration, whereas the effects are minimal in cold black soil areas. The issue may be a mismatch between environmental factors and the choice of returning material, which remains unclear. Here, six sites (each site process manure and straw returning croplands) in the western Northeast China Plain (Fuyu, Longjiang, Tailai, Baiquan, and Kedong Counties, and Nehe City) were chosen to investigate the impact of soil properties (soil clay content [Clay], initial soil pH values [pH], and initial soil organic carbon concentration [initial SOC]), management practices (years of fertilization [Year] and carbon input [C input]), and climate factors (mean annual temperature [MAT], mean annual precipitation [MAP] and mean annual wind speed [WS]) on soil organic carbon concentration (SOC_c). The results showed that in Longjiang and Tailai Counties, OMR had a significantly higher than SWR on SOC_c, whereas in the other four sites, OMR was significantly lower than SWR on SOC_c. Redundancy analysis (RDA) and variance partitioning analysis (VPA) revealed that with OMR, climatic factors, management practices, and soil properties accounted for 40.8 %, 34.9 %, and 20.6 % of the SOC_c, respectively. While with SWR, these factors explained 53.6 %, 12.6 %, and 31.2 %. Among variables, WS was the most influential variable affecting SOC_c changes under OMR, with MAP ranked second in importance. For SWR, Clay and MAP were identified as the two most importance factors. Additionally, SOC is accrul in the part of silt and clay (<0.053 mm) under OMR. For SWR, SOC is accrul in the part of macro-aggregates (>0.25 mm). Thus, for organic materials returning, improving soil water management can promote increased SOC_c. And matching sandy soils to SWR and controlling wind speed during OMR can increase SOC_c effectively. Match organic material returning to multiple factors, emphasizing climate, can lead to more effective increases in SOC_c.