LB 15-139 - Enzyme activities under single species and mixtures of cover crops positively impacts soil carbon availability.

Soil microbial communities drive key soil ecosystem functions; furthermore, they respond rapidly to changes in agricultural management and reflect changes in soil function. Cover crops (CCs) release diverse compounds into the soil through above- and belowground inputs, which significantly impact soil microbial community structure and function, and vary according to cover crop functional group (e.g. legumes, grasses, and oilseeds). However, we know little about the effect of CC diversity and mixes on soil carbon (C), nitrogen (N), and phosphorous (P) availability. Here we hypothesized that more diverse CC mixes would increase nutrient release with subsequent increases in enzyme activities. To explore how CC identity and diversity affect microbial function we evaluated C, N, and P acquiring enzyme activities across a diversity gradient of CC treatments. We used six different CC species representative of three functional groups (i.e., oilseeds, legumes, and grasses). These CC treatments were composed of either single species, four species, or six species, as well as, a fallow control. Enzyme activities were evaluated by fluorometric and colorimetric methods. Total soil C and N, and microbial biomass was also evaluated. C and N acquiring enzyme activity was higher across all CC treatments compared to the fallow control. This is likely due to increased CC derived inputs to the soil. Although acid P enzyme activity was greater than alkaline P enzyme activity, most did not differ between CC treatments and the fallow control. Overall, enzyme activities were positively correlated with total soil C and N. Further, we were able to identify a single species and a mixture of CCs which consistently presented differences against the control. Likewise, single species CCs demonstrated greater enzyme activity in comparison to CC mixtures (4 and 6 species). This result was contrary to our hypothesis suggesting that CC mixes do not significantly increase enzyme activity. CC implementation, more specifically those CCs that increase soil C and N, had a positive impact on C availability and increased C acquiring enzyme activity. It suggests an increase of soil organic carbon and labile C pool due to the accumulation of root exudates in the presence of CCs. This study highlights the influence of single species as well as mixtures of CCs on microbial function, suggesting enzyme activity may be a good indicator of soil ecosystem change associated with the implementation of CCs.