Effect of organic and inorganic K sources and system of rice intensification on growth and yield of genotypically varying rice cultivars

Abstract

A series of trials, including hydroponics and soil experiments, were conducted to document the phenotypic variation among rice genotypes and the response of selected genotypes to inorganic and/ or organic sources of K under standard rice management (SRM) and system of rice intensification (SRI). In a solution culture study, changes in growth attributes under both deficient and adequate K levels indicated differential adaptation of 26 rice genotypes. Three of 26 genotypes, namely, IR-6, Super basmati and 99509, were selected for subsequent studies on the basis of their differential responses for K use efficiency (KUE), shoot biomass, and K uptake at deficient and adequate K levels. The categorization of rice genotypes was made using the index scoring technique. Accordingly, 99509 was categorized as highly efficient-medium responsive, Super basmati as medium efficient-medium responsive, while IR-6 as low efficient-low responsive. Correlation among various growth parameters was calculated, and a strong correlation was found among shoot biomass, KUE, and total K uptake. The growth and yield responses of these selected genotypes were subsequently studied with exogenously applied K (K 2 SO 4 ) in pot trials. On overall basis, the KUE determined the responses of various growth and yield parameters against varying levels of K application. Again, the order of genotypes with respect to KUE was found to be the same as that observed in the hydroponic study, i.e., 99509 was found to be highly efficient, Super basmati was medium efficient, and IR-6 was non-efficient in term of growth and yield attribute formation. A dose of 60 kg K ha -1 was found optimum for increasing most of the growth and yield attributes of the three rice genotypes, which was very close to that calculated amounts obtained using the quadratic model. Keeping in view the cumulative effects, a dose of 60 kg K ha -1 was selected for subsequent field trials. Thereafter, the genotypes were tested under the conventional SRM (continuously flooded) and SRI (intermittently flooded) systems. The growth, yield and quality of the three genotypes were studied under single and integrated use of inorganic and organic K fertilizer. Most of the growth and yield attributes gave maximum response with integrated application of 30 kg K ha -1 as K 2 SO 4 + 30 kg K ha -1 as K-enriched compost under SRM, while 15 kg K ha -1 as K 2 SO 4 + 15 kg K ha -1 as K-enriched compost proved best under SRI. Super basmati gave the maximum grain yield under SRM, while under SRI 99509 was best, both with integrated application of 15 kg K ha -1 as K 2 SO 4 + 15 kg K ha -1 as K-enriched compost. However, maximum straw yield was produced by 99509 with integrated application 1of 15 kg K ha -1 as K 2 SO 4 + 15 kg K ha -1 as K-enriched compost under SRM, while integrated application of 30 kg K ha -1 as K 2 SO 4 + 30 kg K ha -1 as K-enriched compost resulted in maximum straw yield in Super basmati under SRI. IR-6 remained relatively poor in performance in most of the growth and yield parameters. It was note worthy that the genotype 99509, which was rated highly efficient in K use in hydroponic trial changed its response as medium efficient in K use in field trials (both in SRI and SRM), while exactly reverse trend with respect to KUE was observed in case of Super basmati. IR-6 remained relatively poor in growth, yield and KUE under both the systems of management. Total K uptake and KUE of the genotypes varied with K doses and sources under SRM and SRI, affecting the growth and yield parameters of the three rice genotypes tested. Most of the quality parameters under SRI and SRM gave almost similar values, implying that SRI had no negative effect on yield and quality of both coarse and fine varieties of rice. Moreover, SRI was seen to be a viable approach to save water without compromising the yield and quality of the produce, thus it may be adopted as a low-input technology system.