Department of Soils, Punjab Agricultural University, Ludhiana, 141004, Punjab.
*Corresponding author (Email: jasppsingh@yahoo.co.in
1 Krishi Vigyan Kendra (PAU), Haveli Kalan, Ropar, 140 001, Punjab.
The effect of conjoint and separate application of sulphitation pressmud (PM) @ 0.5 and 1.0% and inorganic-P (Pi) @ 25 mg P kg−1 soil was investigated in calcareous Typic Ustiflvents and non-calcareous (Typic Ustipsamments) soil by maintaining aerobic {60% water-filled pore space (WFPS)} and nearly-saturated (90%WFPS) moisture regimes. The combined application of PM and Pi maintained significantly higher Olsen-P in both the soils as compared to their separate application. Combined addition of PM and Pi shifted the solubility points towards super-saturation with respect to dicalcium phosphate dihydrate (DCPD), indicating enhanced P availability. Non-calcareous soil, pre-treated with PM and Pi under nearly-saturated moisture regime exhibited shift in the solubility points above DCPD, as a consequence of lowering of phosphate potential, indicating super-saturation with respect to DCPD. The standard phosphate requirement (SPR) worked out from quantity-intensity (Q/I) relationships revealed decrease in SPR value by 48.9 (45.0%) and 99.4 kg P2O5 ha−1 (90.9%), due to application of PM @ 0.5 and 1.0% under aerobic moisture regime, respectively in calcareous soil. Complete supplementation (89.8 to 100%) was, however, observed in non-calcareous soil under nearly-saturated moisture regime.
P availability, P compounds, phosphate potential, P solubility, standard phosphate requirement, sulphitation pressmud
