Agronomic effectiveness of rock phosphate in an andept of Ethiopia

In a greenhouse experiment, the relative agronomic effectiveness of Togo and Egypt rock phosphate sources were compared with triple superphosphate on high fixing volcanic ash soil of Ethiopia using (Medicago sativa) lucerne as the indicator crop. The P applied ranged from 0 to 160 kg P/ha. In the first cutting, Togo and Egypt rocks were relatively most effective at 60 and 43 kg P/ha, respectively. At these rates, Egyptian rock phosphate was 92% as effective as triple superphosphate compared with 64% for the Togo rock phosphate. Residual values of TSP were also higher than those of the rocks.