Characteristics of Enzyme Activities in Soils within Agricultural Landscapes across Vladimir Opolye High Plains

Abstract

The research was carried out to study the enzyme activities in the gray forest soil (GF) with the second humus horizon (SHH) relative to the fertilizer application system within the agricultural landscapes across Vladimir oblast. The research study was conducted with two soil differences at the multifactor experiment field station in 2021–2023. The reference systems of fertilizer application intensity (for six-field crop rotation) were investigated. Thus, the levels of the fertilizer application intensity were designed as zero (Z) fertilizer + 40 t/ha manure, intense (I) fertilizers N₁₀₀Р₈₀К₁₆₀ + 40 t/ha manure, intense mineral (IM) fertilizers N₃₅₀P₂₂₀K₃₉₀, high-intense mineral (HIM) fertilizers N₄₈₀P₂₈₀K₅₇₅, intense organic and mineral (IOM) fertilizers N₃₁₀P₁₅₀K₃₁₀ + 60 t/ha manure, and high-intense organic and mineral (HIOM) fertilizers N₄₃₀P₁₆₀K₃₆₀ + 80t/ha manure. A steady trend to increasing the catalase and invertase enzyme activities in the GF SHH soils was revealed at the reference systems of fertilizer application. The average catalase activity in the GF soil with the second humus horizon was 23% higher than that in the GF soil at the same soil depth (20–40 cm). The maximum catalase enzyme activity in the experiment was observed at the reference system of intense fertilizer use (I) for the GF SHH soil. Thus, it comprised 2.41 and 1.96 mL O₂/g in the 0–20- and 20–40-cm layers, respectively. T invertase enzyme activity in the gray forest soil with the second humus horizon at the 20–40-cm soil depth was, on average, higher by 30% than that in the gray forest soil. The highest value for this parameter was recorded in two soil differences in the 0–20-cm layer, which comprised 3.50–3.55 mg glucose/g per 40 h. The average humus content in the GF soil with the second humus horizon made up 3.76%, which was 33% higher than that in the GF soil in the 20–40-cm layer. The maximum parameter value within the experiment (0–40-cm layer) was recorded in the GF SHH soil at the reference system of intense fertilizer use, which comprised 4.86%.