Indian Journal of Soil Conservation

A field experiment was carried out during two consecutive years, 1999–2000 and 2000–2001 on clay-loam soils of Udaipur to investigate the residual effect of incubated sources of Udaipur rock phosphate and FYM on soil in wheat-maize cropping sequence. Twenty six treatments were evaluated, viz., 3 sources of Udaipur rock phosphate (URP18%, 31% and 34%), 4 incubation methods (no incubation, incubation with phosphate solubilizing bacteria, incubation with farmyard manure and incubation with farmyard manure + phosphate solubilizing bacteria) and 2 farmyard manure levels (0 and 10 t ha⁻¹) along with 2 checks (40 and 60 kg P₂O₅ ha⁻¹ through DAP). Phosphorus application at increasing levels from 40 to 60 kg P₂O₅ ha ⁻¹ through DAP enhanced available P content in soil after harvest of wheat. Increasesing levels of phosphorus through DAP had no residual effect on bulk density and available N content in soil. Phosphorus status of soil was higher with DAP than URP after harvest of wheat, but after harvest of succeeding maize both the sources were at par. Application of phosphorus through URP reduced bulk density of soil after harvest of crops. More available P in soil was recorded under high grade URP (31% and 34%) than low grade URP (18%). Better availability of P in soil was recorded in URP incubated with FYM and FYM+PSB treatments. FYM application at 10 t ha⁻¹ reduced bulk density and increased available N and P contents in soil after wheat and succeeding maize. Incubated high grade Udaipur rock phosphate may be a viable source of phosphorus in wheat-maize cropping sequence and have equal residual effect to that of water soluble Psources.