Availability of dicalcium phosphate to plants,when applied in various forms

Summary The availability of dicalcium phosphate in powder and granulated form mixed with ammonium sulfate, was tested in a greenhouse experiment. Two soils were used in the experiment: one from Rehovot, neutral and non calcareous, and the other from Gilat, slightly alkaline and calcareous. Clover (two cuttings) was the first crop and cow peas and corn succeeded. The yield results were fitted to Mitscherlich curves. In general, the results of greenhouse and laboratory experiments showed, that in both soils the dicalcium phosphate had approximately the same efficiency as phosphate fertilizer, as did superphosphate. It appears that additions of ammonium sulfate had no appreciable effect on phosphate availability. However, the granulation process lowered its solubility. It may be concluded that there is a possibility that citrate-soluble phosphate could be efficient on calcareous soils no less than the water-soluble form.This research work was financially supported by Fertilizers and Chemicals Ltd., Haifa, Israel.