Biogas slurry change the transport and distribution of soil water under drip irrigation

Biogas slurry (BS), waste water of energy production, holds potential as both an irrigation water resource and a liquid fertilizer source. Typically combined with water and mineral fertilizer at specific ratios, BS is applied in fields with drip irrigation systems to enhance crop growth. However, the soil water infiltration process with BS drip irrigation remains poorly understood, mainly owing to the BS's differing characteristics from conventional water sources. This study investigated the morphological characteristics, transport and distribution of water in three ratios of BS-water using a soil column experiment, with the post-irrigation surface soil pores and elements analyzed using electron microscopy and energy spectrum scanning techniques. The findings reveal that BS drip irrigation significantly alters the water morphological characteristics, transport process and distribution compared to conventional water sources. The morphology of the wetting-front changed from nearly "hemispherical" to a "half-pear" shape with time in BS drip irrigation. The soil-wetting front's vertical distance was notably smaller, approximately 50% of the vertical depth seen with traditional water source drip irrigation, even after redistribution of soil moisture, it was still difficult to reach the depth of the main root zone of most crops. Moreover, The carbon content on the soil surface was increased, ranging between 19.05–47.62% in the BS irrigation scenario, which led to soil pore blockage and a decrease in porosity ranging between 11.99–40.5%. The dynamic viscosity of BS is approximately 50% higher than that of CF.Theses indicate that the combined effect of soil porosity and dynamic viscosity affects the BS infiltration.In conclusion, this paper proposes a BS drip irrigation model with integrated agronomic measures to mitigate the potential adverse effects of BS drip irrigation caused by changes in soil water transportation and distribution.