The rice–edible mushroom pattern promotes the transformation of composted straw-C to soil organic carbon

The application of composted straw in conventional rice cultivation patterns can enhance soil organic carbon (SOC); however, it increases methane (CH4) emission, thereby reducing its net carbon sequestration efficiency in paddy fields. The rice–edible mushroom pattern may improve this phenomenon because edible mushrooms can promote straw decomposition and soil aggregate formation. Here, we investigated the effect of four inoculation amounts of edible mushroom on the transformation of composted straw-C in paddy fields using 13C tracer technology under rice–edible mushroom pattern. The results indicated that the inoculation of edible mushrooms increased the abundance of soil microorganisms and fungal mycelium, reduced SOC aromaticity, and promoted the formation of macroaggregates. Inoculation of edible mushrooms stimulated the transformation of composted straw-C to SOC and reduced its conversion to CH4. The sequestration efficiency of composted straw-C in the soil increased as the inoculation amounts of edible mushrooms increased. When the edible mushroom inoculation amount was 3000 kg ha–1, the highest amount of composed straw-C was sequestrated in soil. With more inoculation amount, more fungal mycelium was produced, which enhanced the physical protection of composted straw-C by promoting the formation of soil aggregates. This study indicated that under the rice–edible mushroom pattern, transformation of composted straw-C to the soil carbon was favored compared with its transformation to CH4, and this conversion efficiency increased with the increasing inoculation amounts of edible mushrooms.