Microbial Response to Winter Cover Cropping Management During Transition to Organic Farming.

The use of cover crops is an effective strategy to provide nitrogen source for following crops in organic farming systems. The aim of our current work is to evaluate: (1) the effect of cover crop species and termination approach on soil microbiological properties and (2) the suitable microbiological parameters for detecting short-term plant residue impacts on soil. In this study, we examined the influence of three legume cover crops [australian winter pea (AP), hairy vetch (HV), and crimson clover (CC)], and three killing methods (flail, spray, and till) on soil microbial biomass C, C and N mineralization, nitrification potential, and enzyme activities (β-glucosidase, exoglucanase, and N-acetyl-β-glucosaminidase). This experiment was conducted on a field during transition to organic farming in North Carolina.

Soil microbiological properties had no significant difference among three cover crop species, but cover crop treatments did show greater soil nitrification potential (0.164 mgNkg^-1h^-1 in average) and higher N-acetyl-β-glucosaminidase activity (0.211 μmolh^-1g^-1 in average) than control soil (0.103 mgNkg^-1h^-1 and 0.155 μmolh^-1 g^-1, respectively). In addition, we observed that flail method increased the values of all the chosen parameters except for net N mineralization compared with the other two killing methods. This might due to the favorable temperature and moisture condition, and higher microbial accessibility provided during operation process of flail method. Our results indicate that nitrification potential and enzyme activity are more sensitive than soil microbial biomass C, C and N mineralization to C input. This knowledge can be important for selecting microbiological parameters for similar future studies.