Effects of biogas slurry on the nutrient content and soil enzyme activity of lime concretion black soil

Abstract

The objective of this study was to evaluate the effect of returning biogas slurry to the field on the fertility indicators of lime concretion black soil in Henan Province, China, with the aim of optimizing agricultural practices and promoting crop nutrient uptake and utilization. Four treatments were set up in the experiment, namely: CK (Control), CF (Chemical Fertilizer), BS50 (Chemical Fertilizer combined with Biogas Slurry Irrigation) and BS100 (Pure Biogas Slurry Irrigation). The application of biogas slurry significantly increased soil enzyme activity, which was particularly prominent in the 20-40 cm soil layer. This enhancement of enzyme activity was closely associated with the delayed senescence of winter wheat roots during the late growth stage, thereby facilitating crop nutrient uptake and utilization. Further analysis revealed a strong correlation between soil fertility status and enzyme activity, indicating that soil enzyme activity can serve as a reliable indicator for measuring the intensity of nutrient transformation. Elevated enzyme activity implies more active nutrient cycling and mineralization processes within the soil system. The decrease in phosphorus and nitrogen content under application of BS is attributed to the higher uptake of these nutrients by the winter wheat plants. Considering the dual requirements of efficient resource use (organic waste utilization), promotion of crop nutrient uptake, biogas slurry treatments were identified as the most suitable measures to improve the productivity and quality of lime concretion black soil under winter wheat cultivation systems.