Effects of film mulching on the spatial distribution of salinity, nitrate nitrogen and ammonium nitrogen in soil under surface and drip irrigations

Abstract: Along with the development of the Benefit strategy in China, film mulching is booming in Hetao Irrigation District because of its advantage in high production. However, for convenience, it is widely combined with surface irrigation in practice, but most studies focused on drip irrigation, thus enough attention should be drawn to the effects of film surface irrigation. The purpose of this study was to investigate the effect of film mulching on the spatial distribution of salt, nitrate, and ammonium nitrogen in the 0-100 cm soil layer under surface irrigation and drip irrigation. The experiment was conducted during the 2021 maize growth season in Hetao Irrigation District. Soil samples in and out of the mulching area were collected and soil salt and nitrogen distribution were analyzed. The results showed that the surface soil (0-20 cm) salt content of surface irrigation and drip irrigation inside the film was lower than that of outside film. In the vertical direction, the soil content was mainly concentrated in the surface soil (0-20 cm). In the horizontal direction, the salt content in the surface soil (0-20 cm) of surface irrigation inside the film was reduced by 55.9% compared with that outside film at the jointing stage of Maize (July 17). In the vertical direction, the soil nitrate nitrogen content decreased with the increase in depth and it was mainly concentrated in the surface soil (0-20 cm). In the horizontal direction, the soil nitrate nitrogen distribution was quite different between surface and drip irrigation. At the jointing stage of Maize (July 24), the soil nitrate nitrogen content outside the surface irrigation film was the largest (46.48 mg/kg) and inside the film was only 4.88 mg/kg, which tended to increase N losses. The trend in the soil nitrate nitrogen content revealed upward shapes from the center of the film to the center outside the film, but the root system of maize was mainly distributed inside the film, which meant the soil nitrate nitrogen content outside the film could be hard to be absorbed. On the contrary, film drip irrigation increased the soil nitrate nitrogen content inside the film (34.18 mg/kg), which was much higher than that outside the film (4.06 mg/kg). Whereas, there was no significant difference in the soil ammonium nitrogen content between the inside and outside film and the soil ammonium nitrogen content was relatively low and stable. Based on the results of this study, we put forward some measures to improve nutrient utilization efficiency. This study provided theoretical and data support for water and fertilizer regulation and high-yield cultivation of maize under film-mulching irrigation in Hetao Irrigation District.