Effect of straw addition on soil infiltration characteristics and model-fitting analysis

Abstract

This study explored the influence of straw addition on the soil water characteristic curves and the soil water holding capacity. Using two different soil bulk densities, soil infiltration was investigated using differently treated straw, i.e., comminuted ammoniated, and blended with inorganic soil conditioner. The experimental results showed that the addition of long straw significantly obstructed soil infiltration. Compared with the control experiment and the comminuted straw treatment, both the addition of ammoniated comminuted straw and the inorganic soil conditioner (Fe (OH)3) effectively improved the soil stable infiltration rate and the cumulative infiltration. After 30 days of culturing, the ammoniated straw treatment affected a more remarkable improvement of the soil structure by reducing the soil bulk density and increasing the soil porosity than did the inorganic soil conditioner treatment. Using a straw and inorganic soil conditioner in combination did not result in a positive interaction for soil improvement. The relative ranking of each treatment on soil infiltration performance was the same for both soil bulk densities. For the soil water characteristic curve of each treatment, both the Philip infiltration model and the van Genuchten (VG) fitting model using RETC software had excellent fitting accuracy. The excellent soil water holding capacity arising from the use of ammoniated comminuted straw at low suction pressures is of significance for soil water preservation in the dry season of the humid region of southern China.