An Innovative Approach for Amelioration of Acid Sulphate Soils in Nilwala River Basin
Abstract:
Paddy tracts of the Nilwala basin have been affected by acid sulphate soils through the implementation of the Nilwala Flood Protection and Drainage Project in 1979. Nearly 7000 acres of lowland paddy lands were abandoned. In these lands, the water table goes down to the level of 50 cm below the soil surface during rain less periods, and soil pH falls to 3-4, causing acid sulphate conditions. Hitherto, several efforts have been made to ameliorate the paddy lands, but none of the solutions were either economical or farmer acceptable. An innovative preventive approach instead of curing where feasibility to increase water table and to keep the jarosie mineral under reduced conditions using natural hydraulic forces was tested. Water table fluctuation in relation to water level in the drainage channel was studied over one year, and a very high correlation (r2=0.985) indicated the possibility of increasing the water table by heading up water in the drainage chan nel. Simulated greenhouse pot experiment revealed that increasing the water table to 15 cm below the soil surface allowed rice plants to grow normally. The recorded plant survival was 112 (53% survival) compared to 28 (15% survival) plants in control. The Recorded mean plant height of Bg. 357 variety was 35.5 cm com pared to 23.0 cm in d treatment and controls, respectively. Soil pH also increased to a value closer to 6.0 in the treatment, which is conducive for rice cultivation. However, the low values of plant survival and plant height were due to unusual low rainfall received in the 2020/21 maha season compared to the 10- year average.
