Leaf nutrient composition, its correlation with yield and quality of sweet orange and soil microbial population as influenced by INM in Vertisol of central India

A field trial was conducted on eight-year-old sweet orange orchards grown on black soils for three years under central Indian conditions. Different treatments involved application of FYM, vermi-compost, wheat straw on nitrogen equivalent basis and green manuring with sun hemp as singly or in combination with inorganic or biofertilizers like Azotobacter and PSB including control plots. The results showed highest concentration of N (2.19%), P (0.111%), K (1.38%), Mg (0.302%), Zn (26.3 ppm) and Cu (16.2 ppm) in the leaves with the combined application of FYM along with 50% dose of inorganic fertilizers and Ca (2.51%) with green manuring with sun hemp along with 50% dose of inorganic fertilizers. Sole application of FYM (to supply 100% N) recorded highest Mn (75 ppm) and Fe (155 ppm) contents followed by combined application of FYM (to supply 75% N) along with Azotobacter and PSB. Significant positive correlation was observed between leaf macronutrients content and fruit yield while leaf Zn content with both yield and quality of fruits. Soil bacterization with Azotobacter and PSb increased their abundance, multiplied well and were able to save 25 per cent dose of organic manures or fertilizers applied for N and P nutrition. Organic manures were highly effective in increasing the microbial population in the soil.