Rainfall Induced Saline Soil Management through Leaching

This study was conducted in the experimental farm of Bangladesh Agricultural University (BAU) to evaluate rainfall-induced leaching of salt in the field soil over time. There were five treatments - I₁:  soil irrigated with fresh water, I₂: soil irrigated with saline water of electrical conductivity (EC) = 4 dS/m, I₃: soil irrigated with saline water of EC = 7 dS/m, I₄: soil irrigated with saline water of EC = 10 dS/m, and I₅: soil irrigated with saline water of EC = 13 dS/m. The treatments were replicated thrice. Soil samples were collected from each plot at 0-20, 20-40, 40-60 cm soil profiles at, usually, 15 days interval. By determining the electrical conductivity of the samples salt leaching pattern in the treatments at different depths was evaluated. Variation of soul pH was also evaluated. At the end of the rainy season, the salt accumulated due to irrigation completely leached out of the top 0-20 cm soil profile in all treatments. The salt from the upper soil profile (0-20 cm) leached down and increased the salinity of the lower soil profiles. At the end of the rainy season, the salinity in the lower soil profile did not reduce to its initial value, implying that the rainfall was not enough to wash out the imposed salinity from the entire root zone soil. At the early period of rainy season, the rainfall was relatively little, but the rate of EC reduction was high, especially in the soil with high salinity (treatments I₄ and I₅). At the later period, on the other hand, the EC reduction rate was relatively low although rainfall was high. It is concluded that, irrigation with high saline water (EC ≥7 dS/m) caused accumulation of salt in excess of that washed out by monsoon rainfall.