An on-farm experiment was undertaken on twelve years old Khasi Mandarin plant in two orchards of Tinsukia and one orchard of Dibrugarh district, Assam during 2002 to 2004 with five different treatment combinations. Highest soil pH, available P2O5, leaf P and K were observed in the treatment receiving Mustard Oil Cake (MOC) (10kg/plant), bio-fertilizers (Azotobacter and PSB) and K2O (600 g/plant) with no inorganic N. Available nutrient balance over the initial content showed maximum mining of nitrogen while positive balance was noticed in case of P2O5 (initial year)and K2O all throughout the years of experimentation. Significantly highest soil Organic carbon (Organic Carbon), available Nitrogen, fruit quality (Juice, Total Soluble Solid, Total sugar, Ascorbic acid) and yield with highest economic return (5.75) were observed where half of the recommended dose of inorganic N and P2O5 were supplemented through Azotobacter and PSB along with K2O (600 g/plant) and Mustard Oil Cake (7.5 kg/plant).
