Relative efficiency of ameliorants on rice productivity in lateritic soils of Kerala

Abstract

The correction of soil pH, reduction of toxic accumulation of native elements and supplementation of secondary nutrients may enhance the growth and productivity of rice grown in lateritic lowlands. A field study was conducted during January to May, 2013 at the rice field of College of Horticulture, Vellanikkara to evaluate the response of soil ameliorants on growth and yield of rice. The experimental design was RBD with 3 replications.Transplanted Jyothi was grown at 15 cm x 10 cm spacing in 5.0 m x 4.0 m plots. The soil was having an initial pH of 5.3. The treatments were amelioration of soil with different amendments such as CaO, dolomite, and ‘Mangalasetright’, which is a commercial product. The ameliorants were applied with or without fertilizer. The package of practices recommendation for low land rice, an absolute control treatment and fertilizer only treatment were also included for effective comparison. Nitrogen and potassium were applied in three equal split doses, first as basal dressing, second at tillering stage and the third at panicle initiation stage. The full dose of phosphorus was applied as basal dressing. CaO @ 377 kg ha -1 together with FYM and NPK, and ‘Mangalasetright’ @ 375 to 774 kg ha -1 constantly maintained a pH of more than 6, which is considered good for rice.Soil amelioration significantly increased the growth characters of rice such as height and tiller count in the presence or absence of fertilizers.Higher doses of ‘Mangalasetright’ resulted in significantly higher LAI than its lower doses.Application of CaO @ 377 kg ha -1 or ‘Mangalasetright’ @ 500 to 774 kg ha-1 together with fertilizer application also resulted in significantly higher improvement in root weight, root spread and leaf chlorophyll content.The leaf chlorophyll content was improved due to the combined effect of soil amelioration, organic manure addition and fertilizer application.The treatment which received the recommended POP for rice cultivation resulted in the constant improvement in rice dry matter production at all the growth stages, which was significantly highest.‘Mangalasetright’ at all the doses and CaO @ 377 kg ha -1 with fertilizer application have produced similar dry matter at 60 DAT and harvest than non application of ameliorants. Ameliorants other than dolomite created a favorable soil environment with an optimum pH and nutrient content which resulted in greater nutrient uptake by crop and consequent development of chlorophyll, enhanced photosynthesis and ultimately higher dry matter production. Amelioration improved all the yield attributes and consequently the yield. Among different ameliorants ‘Mangalasetright performed better than CaO and the lowest effect was observed for dolomite.The highest dose of ‘Mangalasetright’ and the treatment which received POP recommendation resulted in the highest and similar yield of 6.7 t ha-1. The superiority of ‘Mangalasetright’ even in the absence of organic manure addition is attributed to its Mg and S contents. The enhanced growth and yield characters of rice observed in the ameliorated treatments are due to the favorable nutritional rhizosphere environment in the soil and consequent nutrient availability and uptake. While CaO did the ameliorative function ‘Mangalasetright’ did both soil amelioration and secondary nutrient supplementation.