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H. K. Senapati ¹, A. K. Dash ², G. H. Santra ², B. Mohanty ²

Affiliations
1 Department of Soil Science and Agricultural Chemistry, Orissa University of Agriculture and Technology, Bhubaneswar (Orissa), IN
2 Department of Soil Science and Agricultural Chemistry, College of Agriculture, Orissa University of Agriculture and Technology, Bhubaneswar (Orissa), IN

Abstract

The long term fertilizer experiment was designed in Aeric Haplaquept of Bhubaneswar, Orissa with rice-rice cropping system. The treatments comprised of 100% N, NP, NPK (with and without S, Zn, FYM and Weedcide) 50 % and 150 % NPK along with control (no fertilizer) and an additional treatments receiving lime+NPK (based on soil test). In the preceding years substantial yield reductions of kharif rice were observed in the treatment receiving either to K or low rates of K application. Moreover, K balance sheet was found to be negative in all the treatments. In spite of negative K balance there was gain of NH₄OAC extractable K from 10 to 30 kg ha^-1 and loss of non exchangeable K from 17 to 121 kg ha^-1 in all the treatments over initial value. Equilibrium activity ratio (AR Ke) was found to be the lowest 1.2 x 10^-3 (M/l)^1/2 in 100 % NP and highest (3.2 x 10^-3 (M/L)^1/2 in 150 % NPK treatment. Potential building capacity (PBC-K) was highest in the treatment receiving lime + NPK (soil test). Labile K (-DKe) was lowest (2.2 x 10^-2 meq/100 g) in 100 % NP treatment as against 3.4 x 10^-2 meq/100 g in the treatments receiving lime + NPK (soil test). K/N ratio of plant was much lower at the PI stage and also decreased with increasing levels of NPK which showed that K availability was not in proportion to availability of N. K/Fe ratio increased 2 to 3 fold and there was also increase of Mn/Fe ratio of PI stage with increasing levels of K. Variations in K content in plant were found to be significantly related to the variation in equilibrium concentration of K, ARKe, NH₄ OAC-K and HNO₃-K. Fe content in plant decreased with increasing levels of K application. Yields were significantly higher with higher levels of K.

Keywords

Long Term Fertilizer Use, K Nutrition, Rice-Rice Cropping System, Rice Yield.

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