|PHILLIPS, LORI - Agriculture And Agri-Food Canada|
|SEURADGE, BRENT - Agriculture And Agri-Food Canada|
|AGOMOH, IKECHUKWU - Agriculture And Agri-Food Canada|
|DRURY, CRAIG - Agriculture And Agri-Food Canada|
Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2021
Publication Date: 6/12/2021
Citation: Perez-Guzman, L., Phillips, L.A., Seuradge, B.J., Agomoh, I., Drury, C.F., Acosta Martinez, V. 2021. An evaluation of biological soil health indicators in four long-term continuous agroecosystems in Canada. Agrosystems, Geosciences & Environment. 4(2):1-13. https://doi.org/10.1002/agg2.20164.
Interpretive Summary: In general, evaluation of the soil health of an agricultural field provides information that can be used to maintain crop production and to increase crop yield. Currently, changes in the abundance and activities of microbes in the soil are used as indicators of soil health. Previously, a team of ARS scientists from Texas and Minnesota, developed a combined assay (CNPS) that measures microbial activity and provides valuable information on nutrient cycling. This assay was first tested in agricultural soils from Texas and Minnesota, and we wanted to verify if the CNPS assay could be applied to other soils and cropping systems. For this purpose, we selected Canadian soils under long-term monocultures (e.g., corn and soybean) and two grass systems. Teaming with a Canadian scientist, we tested the sensitivity of the CNPS method to respond to management, and to determine its relationship with current indicators of soil health. Our results showed that CNPS distinguished between the four treatments and was related to chemical indicators of soil health, especially those related to soil nutrients and fertility. This study demonstrated the potential of the CNPS assay as a sensitive indicator of soil health.
Technical Abstract: The soil microbial community (SMC) and soil organic matter (SOM) are inherently related and are sensitive to land-use changes. Microorganisms regulate essential soil functions that are key to SOM dynamics, whereas SOM dynamics define the SMC. To expand our understanding of soil health, we evaluated biological and SOM indicators in long-term (18-yr) continuous silage corn (Zea mays L.), continuous soybean [Glycine max (L.) Merr.], and perennial grass ecosystems in Ontario, Canada. The SMC was evaluated via ester-linked fatty acid methyl ester (EL-FAME) and amplicon sequencing. Soil organic matter was evaluated via a new combined enzyme assay that provides a single biogeochemical cycling value for C, N, P, and S cycling activity (CNPS), as well as loss-on-ignition, permanganate oxidizable C (POXC), and total C and N. Overall, soil health indicators followed the trend of grasses > corn > soybean. Grass systems had up to 8.1 times more arbuscular mycorrhizal fungi, increased fungal/bacteria ratios (via EL-FAME), and higher microbial diversity (via sequencing). The POXC was highly variable within treatments and did not significantly differ between systems. The novel CNPS activity assay, however, was highly sensitive to management (up to 2.2 and 3.2 times higher under grasses than corn and soybean, respectively) and was positively correlated (' > .92) to SOM, total C, and total N. Following the “more is better” model, where higher values of the measured parameters indicate a healthier soil, our study showed decreased soil health under monocultures, especially soybean, and highlights the need to implement sustainable agriculture practices that maintain soil health.