Site Specific Nutrient Management Options for Achieving Higher Yields in Cotton and Chickpea under Rainfed Condition

A study was undertaken to delineation of spatial variability of soil fertility status in order to prepare soil available nutrient maps for improved productivity in different crops grown in the study area of Kurnool revenue division in Kurnool district of Andhra Pradesh state using remote sensing and GIS techniques. The Knowledge of spatial-variability is critical for site specific nutrient management in soil fertility to obtain higher yields. Soil sample (350) were collected from surface from 350 selected sites for preparing precise digital maps using point, line and polygon tools of the Geographic Information System (GIS) with ArcGIS software 10.3 was used for database creation and for creating the union of various thematic maps. The spatial variability maps were generated and delineated into different zones for N, P and K. Soil available Nitrogen, Phosphorus and Potassium spatial variability values generated from the thematic maps of Kurnool division were used to establish fertilizer recommendations for cotton in kharif and Chickpea in rabi during  2018-19 seasons. The recommended doses of Nitrogen (RDN) that worked for cotton were 401 to 450, 351 to 400, > 450 and < 350 kg ha-1 for the areas with Nitrogen availability of 140 to 210, 210 to 280, <140 and > 280 kg/ha, respectively. The Phosphorous fertilizer recommendation for soils with available P of < 30 kg/ha and > 30 kg/ha was figured out as > 250 kg ha-1 and < 250 kg ha-1, respectively. For soil available Potassium recorded 230 to 560, < 230 and > 560 kg/ha, the K recommendation was figured out as 301 to 400, > 401 and < 300 kg/ha, respectively. Recommended doses of Nitrogen (RDN) was worked out for chickpea were 51 to 75, > 76 and < 50 kg/ha for the areas with available N ranges of 184 to 280, < 184 and > 280 kg/ha, respectively. The Phosphatic fertilizer recommendation for soils of available P of < 23.5 and 23.5 to 40 kg/ha was figured out as > 200 kg/ha and 171 to 200 kg/ha, respectively. For the soil available potassium recorded 253 to 412, 413 to 570, < 253 and > 570 kg/ha, the K recommendation was figured out as 66 to 100, 31 to 65, > 100 and < 30 kg/ha, respectively.