Effects of nitrogen fertilizer and water management practices on pH and nitrogen distributions in the wetted-soil volume using drip irrigation

In the soil column experiments, the irrigation amount varied from 4.8 to 12 L, and the nitrogen application rate was from 80 to 360 kg ha−1. Three fertigation strategies were tested. The results indicated that an increase in water input led to an increase in the area of pH decrease in the soil at 10 days after the irrigation ended for a given lateral depth of 10 cm. The measurement of nitrogen distribution showed that the nitrogen content in the soil was significantly increased with the nitrogen application rate. Fertigation strategies substantially affect the pH and nitrogen distributions in soil. The strategy of applying water at first for one-fourth of the total irrigation time (1/4W), then applying fertilizer solution for one-half of the total irrigation time (1/2N), followed by applying water for the remaining one-fourth of the total irrigation time (1/4W) made a minimal soil pH decreasing area and a homogeneous nitrate distribution at 0–20 cm depth. Therefore, to reduce NO3-N leaching and avoid deep soil acidification, a dripline depth of 10 cm with an irrigation amount of 4.8 L and a nitrogen application rate of 80 kg ha−1 through the 1/4W–1/2N–1/4W fertigation may be suggested.