Critical factors influencing soil runoff and erosion in sprinkler irrigation: Water application rate and droplet kinetic energy

The water application rate (AR) and droplet kinetic energy are considered the most important indicators of soil erosion in sprinkler irrigation. However, little information is available relating sprinkler performance parameters to soil runoff, infiltration, and erosion. In this study, Nelson R33LP and R33 sprinklers were used in soil container experiments to investigate the effects of the AR and droplet kinetic energy on the runoff occurrence time, surface runoff rate, infiltration depth prior to runoff, infiltration rate, sediment yield, soil loss, and bulk density of the crust during sprinkler irrigation in silty clay loam. The kinetic energy per unit droplet volume (KEd), specific power (SP), and kinetic energy per unit area (KEa) were selected as indicators of the droplet kinetic energy applied by the sprinkler. The results indicate that the runoff occurrence time and the water cumulative infiltration depth prior to runoff were in a negative power function relationship with the AR, SP, and KEa. The final runoff rate and the bulk density of the surface crust increased linearly, while the final infiltration rate decreased linearly with the increasing AR and droplet kinetic energy. During the soil erosion processes, the runoff sediment concentration decreased while the soil loss rate increased and then decreased. Cumulative soil loss increased in the form of power function as the SP, AR, and KEa increased. In short, the AR and SP were critical indicators for predicting the runoff occurrence time, final runoff rate, and infiltration depth prior to runoff under sprinkler irrigation. The SP and KEa were key indicators that affected the final infiltration rate, soil erosion, and surface seal. When the AR increased from 24.16 to 145.30 mm h−1 and the SP increased from 0.09 to 0.55 W m−2, the final runoff rate and cumulative soil loss increased by approximately 850 % and 938 %, respectively, while the final infiltration rate decreased by 63 %. An AR of less than 20 mm h−1 and an SP of less than 0.1 W m−2 are recommended in sprinkler irrigation systems to minimize the risk of soil runoff and erosion for silty clay loam. It is necessary to reasonably select the sprinkler spacing, sprinkler type, nozzle diameter, and operating pressure to reduce soil erosion when designing sprinkler irrigation systems.