Study on the Influence of Fertilizer Solution Concentration on Soil Water and Nitrogen Transport Characteristics Under Film Hole Irrigation

Film hole irrigation is a new technique in agricultural production, which can improve water conservation and increase soil temperature. The purpose of this study was to disclose the effects of fertilizer solution concentration (c) on soil water and nitrogen transport characteristics under muddy water film hole infiltration. The laboratory experiments were conducted with muddy water film hole infiltration, using five fertilizer solution concentration treatments (c = 0, 300, 600, 900, and 1200 mg L−1). The cumulative infiltration, migration distance of the wetting front, soil moisture content, and $$ \mathrm{N}{\mathrm{O}}_3^{-}-\mathrm{N} $$ and $$ {\mathrm{NH}}_4^{+}-\mathrm{N} $$ contents in the wetted body were observed. The models about (i) the relationship between the cumulative infiltration volume per unit film hole area (I(t)) and infiltration duration (t) and (ii) the relationship among the horizontal and vertical migration distances of the wetting front (Fx, Fz), c, and t were established. The results showed that fertilizer solution concentration (c) had a significant effect on I(t), Fx, Fz, and moisture distribution in the wetted body. Cumulative infiltration volume per unit film hole area and infiltration duration conformed to the Kostiakov infiltration model (R2 > 0.98, P < 0.05). $$ \mathrm{N}{\mathrm{O}}_3^{-}-\mathrm{N} $$ is mainly distributed in the range of the wetting radius 12 cm, while $$ {\mathrm{NH}}_4^{+}-\mathrm{N} $$ is mainly distributed in the range of the wetting radius 6 cm. This study could provide a theoretical basis and technical support for fertilizer solution infiltration under muddy water film hole irrigation.