Integrating Fertilizer N Rates with Organics on Soil-Available Nutrients and Yield of Sapota under Semi-Arid Conditions of Karnataka

A field experiment was conducted for three consecutive years to study the effect of various combinations of nitrogenous fertilizer (in the form of urea), vermicompost and FYM on yield and soil-available nutrients in sapota. Largest number of fruits (4820 tree^-1) and maximum fruit yield (31 tons ha^-1) were recorded with 10kg vermicompost + 350:50:450g NPK tree^-1, and was on par with application of 40kg FYM + 350:50:450g NPK tree^-1. The net profit and yield trend over the years showed that application of 10kg vermicompost + 350:50:450g NPK tree^-1 was more suitable for meeting nutrient requirement for enhanced yield in sapota. Application of organics (irrespective of source) showed positive, significant effect on organic matter content of the soil after three years. Highest build-up of organic matter in the soil was recorded with 10kg vermicompost alone (T10), which was at par with 40kg FYM alone (T5). Moreover, there was a clear trend of increasing total soil nitrogen content in plots supplied with increased levels of inorganic nitrogen with organic manures, and, this was subsequently reflected in potentially mineralized nitrogen, suggesting an improved labile pool of plant-available nitrogen. Therefore, there is an obvious need to include organic manures along with the inorganic nitrogenous fertilizer for optimizing the use-efficiency of soil and applied N to achieve sustainable yields in sapota for profit.