ABSTRACT
Field studies were conducted over a two-year period (1993 to 1994) on an Ultisol at Samaru (ll0llIN, 7Â38'E) to evaluate the effect of phosphate rocks and organic waste on maize growth and nutrition. In 1993, the treatments consisted of factorial combinations of three sources of phosphorus (single superphosphate, Sokoto phosphate rock and Togo phosphate rock), three rates of phosphorus (0, 30 and 60kg P205/ha) , and three types of organic amendments (100% cowdung, 50% cowdung + 50% maize cob waste, and 100% maize cob waste) applied at 5t/ha. The treatment combinations were laid out in a split-plot design and cropped to maize. In 1994 the same plots were re-cropped to maize to test the residual effect of the treatments applied in 1993. Maize performance was better with the application of phosphorus and oryanic amendment irrespective of the source. The 30kg P205/ha rate appears to be the optimum when inorganic phosphorus was applied with the organic amendments. In both years agronomic effectiveness of the P sources was in the order single superphosphate > Togo phosphate rock > Sokoto phosphate rock. The agronomic effectiveness of the phosphate rocks relative to single superphosphate was higher in the second year, indicating the high residual value of phosphate rocks. Plant concentration of P and Ca were higher at higher P rates in both years. In 1993, P and Ca contents of the index leaves were significantly higher with single superphosphate than with the phosphate rocks which were statistically at par. However, in 1994 the differences in plant content of P and Ca between single superphosphate and Togo phosphate rock were not significant. In both years, significantly higher P concentration was observed in the index leaves with the application of 100% maize cob waste than with 100% cowdung or 50% cowdung + 50% maize cob waste. It was concluded that the application of organic waste reduced the inorganic phosphate fertilizer requirement of the crop.
