Infiltration simulation and system design of biogas slurry drip irrigation using HYDRUS model

As an unconventional water resource, biogas slurry offers a unique opportunity for efficient utilization of both its water and nutrient contents in drip irrigation systems. However, compared with traditional water source drip irrigation (TWSDI), biogas slurry drip irrigation (BSDI) can alter the movement and distribution of water in the soil, which affects root uptake. Therefore, the relevant parameters of the TWSDI system must be modified based on the characteristics of BSDI infiltration. In this study, a model describing the water transport characteristics of biogas drip irrigation was developed based on the HYDRUS model. The relative error between the measured and simulated results was less than 10 %, thus demonstrating that the HYDRUS model can be used for the BSDI. Based on the different initial soil moisture contents, emitter spacings, and emitter discharges, 18 scenarios were simulated using the HYDRUS model. The results revealed that the intersection wetting depth, vertical infiltration and horizontal wetting distances, and wetting uniformity followed the logarithmic, power, and exponential trends, respectively, against the cumulative infiltration quantity. An optimum combination of system layout parameters was proposed considering the wetting uniformity, amount of biogas slurry dissipation, and cost. In addition, the decreasing order of the weight of factors affecting the susceptibility of biogas slurry infiltration was emitter spacing > initial soil moisture content > emitter discharge, providing an adjustment strategy for improving wet uniformity in common BSDI situations. This study provides a novel optimum strategy for designing biogas slurry drip irrigation systems using the HYDRUS model.