Acidity and nutrient management practices for enhancing soil nutrient availability, nutrient uptake and grain yield of rice in Vaikom kari soils in Kuttanad, Kerala

Abstract

A field investigation was conducted during August to December 2015 and 2016 in farmers` fields in Thalayazham panchayat in Kottayam district. The experiment was laid out in randomized block design having 16 treatments in three replications with rice (Oryza sativa L.) var. Uma. The treatments were dolomite, lime + MgSO4 or RHA (rice husk ash) + MgSO4 along with 100% package of practice (POP) alone or with 100% POP + foliar spray of 13-0-45 N-P-K (KNO3) (1%) or borax (0.5%) or 13-0-45 + borax at PI (panicle initiation) stage. Lime + MgSO4 + 75% POP + 13-0-45 + borax as well as lime without MgSO4 + 100% POP combined with 13-0-45 or borax or both were also included as treatments. Higher grain yield of 5.42 and 5.57 t ha-1 during 2015 and 2016 respectively were produced by dolomite + POP + 13-0-45 followed by dolomite + POP + 13-0-45 + borax and lime + POP + MgSO4 + 13-0-45. The treatments involving dolomite and lime with or without MgSO4 produced taller plants, higher tiller number m-2 and higher Leaf Area Index during both the years. Dolomite + POP + 13-0-45 produced the highest number of panicles m-2. Higher test weight and lower percentage of unfilled grains were observed with dolomite + POP + 13-0-45 and dolomite + POP + 13-0-45 + borax. Lime and dolomite treatments were more effective in reducing soil acidity and improving dehydrogenase activity and nutrient availability in the soil than RHA treatments during both the years. However, the effect of liming materials applied as basal and at 30 DAS diminishes after the crop and this necessitates application of liming materials in every crop season. Availability of soil N improved by treatments involving lime + POP without MgSO4 at PI and harvest stages. The treatments involving dolomite + POP and lime + POP with or without MgSO4 recorded higher available P during PI stage. In general, higher status of available K was registered by the treatments involving dolomite or lime application and lower K status registered by the treatment with 75% POP fertilizer. All treatments involving lime or dolomite registered higher soil available Ca and those involving dolomite or lime + MgSO4 showed higher availability of Mg in the soil. The treatments involving dolomite registered lower status of soil available Fe and higher status of available B. Higher status of available Zn was registered by the treatments involving dolomite or lime + MgSO4. Soil pH was significantly and positively correlated with available P, Ca and Mg and significantly and negatively correlated with available Fe in the soil. In general, higher uptake of macronutrients was observed with dolomite or lime + MgSO4 treatments along with 100% POP during both the years. Foliar spray of 13-0-45 recorded higher N and K uptake. Significant and positive correlation of grain yield with uptake of macro nutrients was also observed.