Kinetics of nitrogen in sodic soil of Kumulur village, Trichy District, Tamil Nadu under different organic and inorganic amendments

Currently more than 20 per cent of the world’s irrigated land is salt affected. Of that about 60 per cent are sodic soils, warranting greater attention for efficient and eco-friendly environmentally amelioration techniques. Transformation and availability of several plant nutrient elements are affected by soil sodicity. Alkali/sodic soils are to be reclaimed so as tomake nutrients available to plants optimally. A laboratory incubation study was examined to analyse the impact of various amendments, either alone or in combination with nitrogen (N) @75 kg/ha, on the physico-chemical characteristics and nitrogen dynamics in sodic soil of Kumulur village Trichy District, Tamil Nadu (pH-10.4, EC-0.40 dS, m-1, ESP-31.8). The investigation was conducted at ADAC&RI in Trichy with three replications and eight treatments in a completely randomized design. The treatments used for sodic soil reclamation utilizing a standardized procedure were Gypsum (GYP) + Green manure (GM) @ 6.5 t ha-1 (T2), Distillery spent wash (DSW) @ 5 lakhs liter-1(T4), and Green leaf manure (GLM) @ 12.5 t ha-1(T3). Soil samples were taken at 15-day intervals from the 15th to the 60th day and tested for NH4-N, NO3-N, and accessible nitrogen. Using DSW, GYP + GM, and GLM, the pH of the water was decreased from 10.2 to 8.37, 8.42, and 9.21, respectively. The soil pH dropped the most in the DSW-controlled treatments. The application of nitrogen alone without any amendments (T5) recorded a higher value (135 kg ha-1) during an initial period (15 days) only and thereafter declined sharply due to various losses, i.e., volatilization, denitrification or fixation. When nitrogen was applied along with amendments, a significant (CD-0.05%) buildup in available N contents was observed over the application of N alone. Available nitrogen (325 kg ha-1), nitrate nitrogen (102 kg ha-1) and ammonical nitrogen (205 kg ha-1) were significantly increased due to the addition of amendments. However, the decline in available N with incubation period was only marginal when nitrogen was applied along with amendments. An increase in NH4-N at 30 DAI might be due to the release of nutrients. A slight increase in the nitrate-N content of the soil was observed at the end of the incubation period due to microbial oxidation of NH4-N to NO3-N. The application of amendments could save a quantity of N dose besides reclaiming the sodicity