When are you measuring soil ß-glucosidase activities in cropping systems?

Authors: Lehman, Richard; Osborne, Shannon; Ewing, Patrick

Submitted to: Agricultural & Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2024
Publication Date: 10/22/2024
Citation: Lehman, R.M., Osborne, S.L., Ewing, P.M. 2024. When are you measuring soil ß-glucosidase activities in cropping systems?. Agricultural & Environmental Letters. 9(2). Article e70002. https://doi.org/10.1002/ael2.70002.
DOI: https://doi.org/10.1002/ael2.70002

Interpretive Summary: Cellulose is the most abundant biopolymer in terrestrial biomes and its decomposition is central to global carbon and nutrient cycles. Soil extracellular beta-glucosidase enzymes perform the final and potentially limiting step in cellulose decomposition producing glucose which is readily available to soil microorganisms for C and energy. As such, the measurement of soil extracellular beta-glucosidase activity and its linkage to land management is of ecological significance. The temporal variation in beta-glucosidase enzyme activities and the factors that drive these activities are not defined. We measured soil beta-glucosidase activities biweekly over a period of four months in a cropping systems field experiment. Surprisingly, we found temperature and precipitation had no value in predicting enzyme activities. Enzyme activities were affected by crop rotational diversity, but also responded to the current crop and the 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 processing and stabilization.

Technical Abstract: In situ soil respiration is driven by annual patterns of temperature and soil moisture; but, what about extracellular enzyme activities responsible for depolymerizing organic matter? We conducted biweekly measurements of potential soil extracellular ß-glucosidase activities during a four-month period from soil thawing to the end of July in annually cropped field plots. Our objective was to determine the best sampling time to resolve effects of crop rotational diversity on soil microbial activities. Potential ß-glucosidase activities were high 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, activities were affected by crop rotational diversity and responded to the current crop and the 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.