Modelling of Soil Moisture Movement and Solute Transport in Parts of Malaprabha Command

Infiltration is one of the most important hydrological process through which water enters the soil surface and plays a significant role in controlling soil water storage, crop yields, irrigation efficiency and solute entry into the soil profile. In agriculture fields, generally, the top soils are enriched with high organic matter and clay, particularly in black soils that promotes sorption, biological degradation and transformation of contaminants. During the process some of the chemicals applied to farm land, move down with the deep percolating water from the root zone and there are likely chances to pollute the underlying ground water. Such instances are reported by locals in areas dominated by black soils of Malaprabha command area. In order to understand the extent of groundwater contamination through chemical fertilizers, insecticides and manures, two agricultural plots (sugarcane and banana plantation) have been identified in parts of Malaprabha command area covering parts of Saundatti, Ramdurg (Belagavi district) and Nargund taluks (Gadag district). Hydraulic properties such as infiltration and hydraulic conductivity were determined in the field. Soil samples were collected and analysed in the laboratory for texture and porosity. The study indicated that the soils of the region are layered in structure. Further, it is noticed that the coarse textured loamy soil is present below the fine textured soils (such as silty loam or clayey loam). Due to the presence of fine soils at the top, the irrigated water get accumulated and the evaporation takes place relatively faster and results in the accumulation of excess salt. It is also noticed that the layered soils have obvious effects on solute transport and salt accumulation in the clay rich soil layer at the interface. The average salt accumulation (Total Nitrogen) observed in the study area within soil profile is 18.7g/kg. The maximum salt accumulation (21.38 g/kg) occurred in the top layer of sugarcane plots followed by banana plantation (19.85 g/kg). It is also noticed that there are remarkable changes in the interlayered soils with reference to water infiltration characteristics and salt leaching intensities. Study revealed the fact that the properties of the soil profile with a silty loam interlayer is better than with a silty clay loam interlayer.