Cover crop residue diversity enhances microbial activity and biomass with additive effects on microbial structure

Abstract

Context Cover crops are used to improve soil fertility and environmental sustainability. Decomposition of cover crop residues can affect belowground microbial communities and activity, which is important for soil functions (e.g. nutrient cycling, organic matter decomposition). Aims We investiagated the effect of plant residues from a range of cover crop species on soil microbial activity, diversity and microbial community composition. Methods A mixture of four cover crop residues (buckwheat, clover, sunflower, radish) or an equal mass of the residues of each of the individual species were assessed for their effect on soil respiration and soil microbial community structure. Key results Cover crop residue incorporation significantly (P < 0.001) increased soil respiration during 84 days incubation and this response caused a significant change in microbial community composition by increasing the proportion of fungi and Gram-positive bacteria at the cost of decreasing Gram-negative bacteria. The mixture of cover crop residues had a significantly (P < 0.05) greater soil respiration rate, by 57.61 μg C g−1 h−1, than the average of the four individual residues, but did not have a significantly different soil microbial biomass or microbial community structure. Conclusions Greater diversity of organic resources increased the number biochemical niches, and activated dormant microbial communities to increase activity without affecting biomass or community composition. Greater respiration from similar microbial biomasses suggests that microbial activity might be more efficient following more diverse substrate input. Implications The positive impact of cover crop residues on soil microbial activity suggests that mixtures of cover crop residues may enhance soil functions beyond the sum of individual cover crop residues.