An evaluation of biological soil health indicators in four long‐term continuous agroecosystems in Canada

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 (ρ > .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.

Modeling of total and active organic carbon dynamics in agricultural soil using digital soil mapping: a case study from Central Nova Scotia

“…Although POXc exhibited strong responses to changes in management practices in our short-term analysis, Pérez-Guzmán et al (2021) reported highly variable POXc responses between management treatments in Ontario, Canada, and highlighted the use of more sensitive indicators, such as the combined enzyme assay technique. In addition, our study could not differentiate between pasture, grassland, and forage fields due to the inadequate spatial resolution of the satellite imagery and lack of reliable agricultural land use information.…”

Enzyme activities as soil health indicators in relation to soil characteristics and crop production

“…It is likely that the availability of N substrate from N fertilizer, shorter duration of experiment, and medium‐textured soil favored AST activity in Sidney compared with absence of N fertilization treatment, longer duration of the experiment, and coarse‐textured soil in Froid. Several researchers (Klose & Tabatabai, 1991; Perez‐Guzman et al., 2021) reported that AST activity was related to SOM and STN.…”

“…Bowls et al (2014) reported that BG activity was associated with increased N availability and NAG activity associated with increased C availability. Some researchers (Caudle et al, 2020;Perez-Guzman et al, 2021;Reardon et al, 2019) demonstrated that BG and NAG activities were related to phospholipid-derived fatty acid (PLFA), KMnO 4 -extractable C (POXC), SOC, STN, and autoclaved citrate-extractable protein (ACEP). The NAG activity was correlated to potentially mineralizable N (PMN), SOC, microbial biomass C, and PLFA (Muruganandan et al, 2009).…”

“…Muruganandan et al (2009) showed that NAG activity was related to PMN, microbial biomass C, and PLFA. Some researchers (Caudle et al, 2020;Perez-Guzman et al, 2021;Reardon et al, 2019) found that BG and NAG activities were related to PLFA, POXC, and ACEP. Our results showed limited association between AST activity and labile C and N fractions at both sites, indicating that AST activity was not effective in enhancing microbial biomass and activity and N mineralization compared with other enzyme activities.…”

Soil Health and Biodiversity Is Driven by Intensity of Organic Farming in Canada

“…Shorter crop rotations, especially when including low residue crops such as soybean or potato, leads to a decline in SOC stocks as found in more intensive farming systems in Eastern Canada (Nyiraneza et al, 2017;Perez-Guzman et al, 2021). More diverse or extended crop rotations are recommended in organic farming systems, to maintain and enhance SOC, although this practice on farm may vary with scale and intensity of the farm operation (Lynch et al, 2014a;Lynch, 2015).…”