Effect of Tillage and Phosphorus Fertilization of Wheat on Inorganic Soil Phosphorus Fractions under Wheat-Sorghum Cropping System

Soil samples were drawn in rabi season of 2013-14 from an ongoing experiment initiated in 2011 on “Phosphorus management in wheat under different tillage practices in sequence with sorghum crop” at the Research Farm of CCS HAU, Hisar. The experiment is laid out in a split plot design with four replications with four tillage treatments (Zero Tillage, conventional tillage and minimum tillage) and four P rates in wheat only at 0, 45, 60 and 75 kg ha-1. P fertilization caused a significant increase by 36.5, 64.7 and 140.8% in Saloid-P over control while under zero tillage (ZT) it was only 12.0 and 4.5 %, respectively over conventional (CT) and minimum tillage (MT). Saoid-P was the least amongst all the fractions and constituted only about 2% of inorganic P extracted from the samples. A slight insignificant increase in the Al-P or Fe-P in surface soil (0-15 cm) over ZT, CT and MT while P application increased the values from 34.2 in control to 50.4 for 75 kg dose for Al-P while the corresponding values for Fe-P were 42.0 60.6, respectively. Distribution in different fractions followed the sequence: Ca-P > Fe-P > Al-P > Saloid-P and all these fractions were significantly interrelated.