Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2019
Publication Date: 6/4/2019
Citation: Acosta Martinez, V., Perez-Guzman, L., Johnson, J.M. 2019. Simultaneous determination of ß-glucosidase, ß-glucosaminidase, acid phosphomonoesterase, and arylsulfatase in a soil sample for a biogeochemical cycling index. Applied Soil Ecology. 142:72-80. https://doi.org/10.1016/j.apsoil.2019.05.001.
Interpretive Summary: Farmers and those that advise farmers and land owners desire simple, rapid tests that will assess soil health. A healthy soil has the capacity to cycle plant essential nutrients like phosphorus (P), sulfur (S), nitrogen (N) and carbon (C) using enzymes. Four enzymes activities have been targeted as indicators of changes in soil health due to agricultural practice. However, the current protocol requires analyzing each enzyme independently as soil health indicators, but requiring more time and resources. Therefore, ARS scientists from Lubbock TX and Morris MN suggest measuring four enzyme activities simultaneously in the same soil sample to provide as index of soil health. This approach will reduce cost, time, resources and waste generated by four times, and will benefit producers, action agencies, and soil testing laboratories interested in monitoring and enhancing soil health.
Technical Abstract: Four enzymes activities (EAs) have been targeted as soil health indicators for their important role in reactionsreleasing bioavailable nutrients within C (ß-glucosidase), N and C (ß-glucosaminidase), P (acid phosphomo-noesterase) and S (arylsulfatase) cycling. Traditionally these EAs are assayed independently on air-dried soil bymeasuring the release ofp-nitrophenol from a substrate analog. Previously, we suggested a novel approach toassess multiple EAs simultaneously in the same soil sample by adding two or three substrates to obtain acomparable index. Our current study provides a combined assay for simultaneous determination of these fourEAs in the same soil sample. For the incubation step of our combined assay, we tested modified universal buffer(MUB) because it is used for assayingß-glucosidase and acid phosphomonoesterase activities and tested acetatebuffer as it is used for assayingß-glucosaminidase and arylsulfatase activities. Using the acetate buffer (pH 5.8)for the combined assay showed the lowest percent of difference (average of-14%) compared with the sum ofindividual EAs, and showed positive significant correlations (p< 0.001) with the sum of the individual EAs(r= 0.97) and with soil organic C (r= 0.94) and total nitrogen (TN) (r= 0.93). This combined acetate bufferassay (“CNPS activity”)differentiated among agroecosystems similarly to the sum of the individual EAs in Texassoils (cotton < grass < Conservation Reserve Program) and both approaches showed a tendency for higheractivities in a diversified rotation compared to corn-soybean and a grass system for Minnesota soils. Use of thenovelCNPS activitywill provide a uniform biogeochemical cycling index while reducing time and resourcescompared to assaying the EAs individually.