Department of Agricultural Chemistry and Soil Science, Gujarat Agricultural University, Junagadh Campus, Junagadh, Gujarat, 362 001.
* Present address: College of Agriculture, Gujarat Agricultural University, Sardar Krushinagar, Gujarat, 385 506.
A laboratory incubation study was conducted to know the effect of different levels of phosphorus (0, 50, 100 ppm P), moisture (field capacity-M1 and saturation-M2) andorganic matter (0,2.5,5.0%) at different time intervals (7, 14, 28, 56, 112 days) on the phosphorus availability and its fractions in two calcareous soils (5.0-S1 and 33.5%-S2 free lime). Saloid-P and Al-P decreased with increase in time, but the reverse was true in the case of Fe-P and Ca-P. However, Red, S-P, increased with increase in time upto 56 days but thereafter it decreased but Occlo-P behaved exactly in the reverse. Saloid-P, Al-P, Fe-P, Red S-P, Occl.P, Ca-P and Olsens P were significantly higher in S2 than in S1. Application at all the levels significantly increased various P fractions over its no application. Al-P, Fe-P, Redo, S-P, Occl-O-P. Org.-P and Olsen's P was significantly higher under M2 over M1, whereas saloid-P and Ca-P were significantly lower in the former than in the latter. The organic matter at 2.5 and 5 per cent significantly increased the content of Occl.-P. Org.-P and Olsen's-P, whereas saloid-P was significantly affected only at 2.5 percent level.
Phosphorus fractions, calcareous clay soils, water, organic mater, availability of P
