Emerging multiple nutrient deficiencies have necessitated renewed efforts to address nutrient management issues and integrated use of inorganic fertilizers through organic manures and microbial biofertilizers. Accrued long term field data showed much better effectiveness of microbial consortium (MC) when used in combination with inorganic fertilizers and organic manures, FYM or vermicompost, however latter could produce much higher magnitude of response. The net increase in canopy volume within three years (2007–11) with 100% RDF was 1.54 m3 compared to 2.34 m3 with 75% RDF plus 25% vermicompost (Vm) plus MC, with a much favourable fruit quality parameters (48.8% juice, 9.7% TSS and 0.70% acidity). Soil quality parameters in terms of soil microbial biomass (SMB) was much higher (68 x 103/g soil as bacterial count and 41 x 103/g soil as fungal count) and soil microbial biomass nutrient (SMBN) (202.5 mg/kg Cmic, 49.4 mg/kg Nmic and 24.5 mg/kg Pmic) with 75% RDF plus 25% Vm plus MC compared to SMB (32 x 103/g soil as bacterial count and 16 x 103/g soil as fungal count) and SMBN (152.1 mg/kg Cmic, 19.1 mg/kg Nmic and 16.1 mg/kg Pmic) with exclusive use of inorganic fertilizers as 100% RDF. These changes within rhizosphere were very well translated into consequent improvements in leaf nutrient composition, being significantly higher (2.28% N,0.12% P,1.42% K,36.4 ppm Fe – 32.8 ppm Mn – 7.3 ppm Cu – 22.6 ppm Zn) with 75% RDF plus 25% Vm plus MC over 100% RDF (2.13% N,0.08% P,1.23% K, 30.3 ppm Fe, 28.4 ppm Mn, 7.3 ppm Cu, 19.3 ppm Zn). These observations lend strong support in favour of INM-based treatments than sole use of inorganic fertilizers in the context of offering some restraint of menacing nutrient mining induced decline in citrus orchard productivity.
Nagpur mandarin, canopy growth, yield, quality, soil microbial biomass, soil microbial biomass nutrients, soil carbon fractions, leaf nutrient composition
