Effects of lateral depth and emitter discharge rate on pH and nitrogen distributions in the wetted‐soil volume using drip fertigation

Abstract

AbstractAccelerated soil acidification from excessive nitrogen fertilizer use and unreasonable irrigation has seriously increased. The advantages of saving water and fertilizer make drip irrigation feasible for reducing soil acidification. However, it is still unknown how drip irrigation influences the distribution of pH in the soil. Experiments were conducted in 30° wedge‐shaped plexiglass containers to study the transformation of nitrogen and the distribution of pH in the soil profile under subsurface drip irrigation. The apparent cylindrical water application rate varied from 4.8 to 12 L, the emitter discharge rate varied from 1.8 to 5.5 L/h, and the lateral depth ranged from 0 to 20 cm. Ten days after irrigation ended, a lateral depth of 20 cm noticeably reduced soil pH at a depth of 10–40 cm, while the pH at a shallow lateral depth decreased in the topsoil; similarly, an emitter discharge rate of 1.8 L/h significantly decreased soil pH at a depth of 0–40 cm, while the pH with a greater emitter discharge rate was slightly decreased in the topsoil. Furthermore, an increase in the application rate resulted in an increase in the area of pH decrease in the soil at 10 days after irrigation ended. Additionally, the growing nitrogen application rate significantly increased the nitrogen content in the soil profile, and the potential risk of deep‐soil pH declined. To reduce NO3‐N leaching and avoid deep‐soil acidification, a dripline depth of 10 cm with a minor irrigation level and nitrogen application rate through an emitter discharge rate of 3.2 L/h may be suggested.