Study of distribution of various fractions of Phosphorous as influenced by long term nutrient management practices in Vertisol

A long term field experiment was conducted at Instructional Farm of College of Agriculture, Indira Gandhi Agricultural University, Raipur, Chhattisgarh to evaluate the effect of long term nutrient management practices on distribution of various fractions of Phosphorous in Vertisol. The experiment was consisted 5 treatment replicated four times in a randomised block design. The treatments were T1 (control), T2 (GRD), T3 (YT 5t ha-1), T4 (YT 6t ha-1) and T5 (YT 6t ha-1 with FYM). Fertilizer prescription equation for rice developed in previous under STCR project as FN =4.05T-0.57SN-0.78 ON, FP = 1.46 T - 3.09 SP-0.31 OP and FK = 1.61 T - 0.10 SK -0.14 OK were used to calculating the fertilizer doses for yield targeted treatments. Initial soil value of phosphorus under different treatments was varied from 6.13 to 25.40 kg ha-1due to long term nutrient management practices. All the P fractions were significantly higher in T2 followed by T5, T4, T3 and lowest in T1. All P fractions (Saloid, Al, Red, Fe, and Ca P) were recorded higher values with the treatment T2 (GRD) due addition of a large amount of phosphorous applied in soil. The sequential order of dominance of different forms of phosphorus in Vertisol were “Ca-P > Red-P > Fe-P > Al-P >Saloid-P”. The percentage contribution of different fractions to the total P was in the order of “Ca-P > Red-P > Fe-P > Al-P >Saloid-P. The highest grain and straw yield were recorded in T5 (YT 6t ha-1 with FYM) followed by T4 (YT 6t ha-1), T2(GRD) and lowest in T1(control). Among different P fractions, Red-P was found the most important P fractions contributing toward grain yield with ‘R2’values 0.88.