2.3. Computation of mineral fertilizers
Since, wide variations in soil fertility across the cane producing zones, a workable targeted yield equation (TYE) for plant (FN = 7.37 T– 1.95 SN, FP2O5 = 0.96 T–2.21 SP and FK2O =3.36 T– 0.83 SK) and ratoon crop (FN = 5.91 T–1.83 SN, FP2O5 = 0.64 T–1.85 SP and FK2O =2.33 T–0.60 SK) were used for balance fertilization in different cane producing zones by employing initial soil test value and defined targeted cane yield. A wonder sugarcane variety (Co 0238) which covered larger area (alluvial soil) in Uttar Pradesh was used for developing TYE during 2016–17 and 2017-18 by considering nutrient required to achieve per Mg cane yield, utilization efficiencies of nutrients available in soil and those applied through inorganic fertilizers were considered for developing TYE (Ramamoorthy & Velayutham 1971).
where, FN, FP2O5 and FK2O are mineral fertilizers N, P2O5 and K2O (kg ha−1); SN, SP and SK are initial soil test values estimated before planting. To make symmetry, P2O5 and K2O were converted into P and K by applying factor 2.29 and 1.20, respectively. T-targeted cane yield (Mg ha−1). N, P2O5 and K2O fertilizers were calculated on the basis of above equations for balance fertilization.