Effect of Organic and Inorganic Source of Nitrogen on the Nutrients in Soil and Soil Solution and Growth of Rice

A greenhouse experiment was conducted to study the changes on the nutrients in soil and soil solution and growth of rice treated with organic manures, viz. farmyard manure, Sesbania rostrata, Sesbania aculeata and prilled urea (PU). The nitrogen was applied @ 60 kg N ha⁻¹ and rice variety ‘Ratna’ was used as the test crop. Incorporation of organic and inorganic sources of N increased soil and soil solution NH_4⁺-N to apeak and then declined to a very low level. Prilled urea gave higher NH_4⁺-N than did organic sources at 2 weeks after flooding (WAF) whereas the reverse trend was obtained at 6 WAF indicating slow release of N from organic manures. The concentration of P, K⁺, Fe²⁺ and Mn²⁺ in the soil and soil solution were higher with PU and organic sources than control. Addition of N, regardless of sources, increased grain yield significantly. Nitrogen and Mn uptake by grain also increased significantly with the addition of N.