Simulation of Soil Moisture Movement and Solute Transport Characteristics in Parts of Malaprabha Sub Basin

Abstract

AbstractIn recent years, the advancement in agriculture with special emphasis on crop yield has encouraged farmers to apply large quantities of fertilizers and pesticides. As the top soils are enriched with high organic matter and clay, particularly in black soils, promotes sorption, biological degradation and transformation of contaminants. During the process, some of the chemicals applied to farmland, move down with the deep percolating water from the root zone and pollute the underlying groundwater. Therefore, the present study was carried out to understand the effects of different soil texture configurations on water movement and solute transport to provide a reliable scientific basis for the application of negative‐pressure irrigation (NPI) technology. Two agricultural plots (Sugarcane and banana plantation) located in parts of the Malaprabha sub-basin covering parts of (Belagavi district) were identified, and the transport process was modelled using a HYDRUS-1D model. Hydraulic properties such as infiltration, hydraulic conductivity and soil textures were determined using field and laboratory methods. It is observed that in the layered soils, when a coarse texture of loamy soil is present below the fine textured soils such as silty loam or clayey loam, irrigation water accumulated in the top soil, and this led to an increase in evaporation compared with the homogeneous loam profile. However, fine texture silty loam or clay loam layers beneath the loamy soil was more conducive to water infiltration into the lower layer, and this increased the amount of water infiltration and simultaneously reduced the surface evaporation effectively. It is also noticed that the layered soils have obvious effects on solute transport under NPI, and salt accumulation readily occurs in the clay‐rich soil layer at the interface. The average salt accumulation observed in the study area within the soil profile is 19.87 g/kg. The maximum salt accumulation that occurred in the top layer is 24.54 g/kg in the sugarcane plots and 17.85 g/kg in the banana plantation. The study also indicated that interlayered soils showed remarkable changes in the water infiltration characteristics and salt‐leaching intensities under NPI, and also indicated that the properties of the soil profile with a silty loam interlayer are better than with a silty clay loam interlayer.KeywordsInfiltrationSoil moistureSolute transportHYDRUS-1D and negative pressure irrigation