Comparative Effectiveness of Nitricphosphates as a Source of Fertilizer Phosphorus to Berseem (Trifolium alexandrinum)

The comparative effectiveness of nitricphosphates relative to some of the water-soluble and the water-insoluble sources of fertilizer P was studied on Tolewal loam soil, using berseem var. Mescavi (local variety) as a test crop. The different P fertilizers were applied to berseem å 0.25,50,75 and 100 kg P₂O₅/ha. The estimates of regression coefficients obtained by using a model of concurrent straight line responses were employed to determine availability coefficient ratios. Taking superphosphate as the standard, effectiveness of nitricphosphates increased with the proportion of their water-soluble P fraction. Dicalcium phosphate and superphosphate were almost equal in their effectiveness. Rock phosphate was the least effective source of fertilizer P.

Equilibrium phosphate potentials and extractability coefficient ratios, obtained in the laboratory, correlated with availability coefficient ratios obtained from plant attributes. This suggests that relative efficiency of new fertilizer can be estimated by incubating them with the soills in the laboratory.