COS 89-2
Effects of straw return on carbon dynamics in agricultural soils: A meta-analysis
Straw return has been widely recommended as an environmentally friendly option to manage carbon (C) sequestration in agricultural ecosystems. However, the overall trend and magnitude of changes in soil C in response to straw return remain uncertain. In this meta-analysis, we calculated the response ratios of soil organic C (SOC) concentrations, greenhouse gases (GHGs) emission, nutrient contents and other important soil properties to straw addition in 176 published field studies.
Results/Conclusions
Our results indicated that straw return has significantly increased SOC concentration by 12.8% on average, with a 27.4% to 57.6% increase in soil active C fractions. CO2 emission has increased in both upland (27.8%) and paddy systems (51.0%), while CH4 emission increased by 110.7% only in rice paddies. N2O emission has declined by 15.2% in paddy soils, but increased by 8.3% in upland soils. Responses of macroaggregates and crop yield to straw return were significantly and positively linear with the increments in SOC concentrations. Straw-C input rate and clay content significantly affected the response of SOC. Significant positive regression relationship was found between annual SOC sequestered and duration, which suggested that soil C saturation would occur after 12 years under straw return. Overall, straw return was an effective means to improve SOC accumulation, soil quality and crop yields. Straw return induced improvement of soil nutrient availability may favor crop growth, which could in turn increase ecosystem C input. Meanwhile, analysis on net global warming potential (GWP) balance suggested that straw return increased C sink in upland soils, but increased C source in paddy soils due to enhanced CH4 emission. Our meta-analysis suggested that future agro-ecosystem models and cropland management should differentiate the effects of straw return on ecosystem C budget in upland and paddy soils.