Does Straw Return Strategy Influence Soil Carbon Sequestration and Labile Fractions?

Returning the crop residues has been documented to increase soil carbon storage. However, the impacts of different straw return strategies on soil C fractions and sustainable crop productivity are not fully understood. Here, we investigated the impact of different residue management systems on grain yields, SOC sequestration, and soil C fractions in a wheat (Triticum aestivum L.)-maize (Zea mays L.) double cropping system over 6 yr. The straw return strategies included no straw return (CK), conventional wheat straw return (WC), modified wheat straw return (WM), conventional maize straw return (MC), modified maize straw return (MM), conventional straw return for both wheat and maize (WC+MC), and modified straw return for both wheat and maize (WM+MM). The annual average grain yields of maize and wheat when compared to crop residue removal were increased by 32.5 and 50.5% than when the wheat straw and corn stover was not harvested, respectively. Compared to the initial value, the SOC stock increased over a 6 yr by 16.4% period when the wheat straw and corn stover was not harvested. The concentrations of microbial biomass C, very labile C, labile C, KMnO₄-oxidizable C, and C management index were increased by returning the crop residue. Overall, the results suggested that the integrated and modified return strategy of both wheat and maize straw is an optimal way of sustainable crop production under the intensive wheat-maize double cropping rotation in the North-central Plain of China. [ABSTRACT FROM AUTHOR]