Biweekly soil betaglucosidase enzyme activities and weather data

In situ soil respiration is driven by annual patterns of temperature and soil moisture; but, what about extracellular enzyme activities responsible for depolymerizing soil organic matter? We conducted biweekly measurements of potential soil β-glucosidase activities during a four-month period from March soil thawing through July in annually cropped field plots in eastern South Dakota. Our objective was to determine the best sampling time to resolve effects of crop rotational diversity on soil microbial activities. Potential β-glucosidase activities were elevated immediately following soil thaw, peaked in May, and declined to their lowest value in mid-summer. Temperature and precipitation had no value in predicting enzyme activities; however, enzyme activities were affected by crop rotational diversity and responded to current crop and previous crop. These findings are pertinent to the use of soil extracellular enzymes in soil health assessments and as indicators of microbial substrate preference with implications for soil carbon stabilization.

Methods
We measured betaglucosidase activities on soil samples collected at biweekly intervals from a corn-soybean rotation and more diverse four-year crop rotations that each included corn and soybean. As every crop is present every year in these field plots, we sampled all crop phases for each rotation within a single year to examine the effects of the entire rotation, current crop, and previous crop under identical weather conditions.  On-site weather station recorded daily temperature and precipitation for the study duration.