Effect of the Phosphate Fertilization on the Production of Apple Trees Planted in Calcareous Alluvial Soil

Abstract

To test the effect of phosphate fertilization on the production of the Tunisian local apple variety "Llorca" planted on alluvial, highly carbonated and silty to silty clay soil, an experimental protocol consisting of a test block with 5 treatments and three repetitions has been applied. The five treatments are doses of bi-ammonium phosphate (DAP) varying between 0 and 200 kg/ha, spaced 50 kg/ha of each other. They have been applied by plowing on three rows located in the middle of the studied orchard. At the end of the cropping season, analyzes on available P2O5 (Olsen) under each tree and P content of dry matter of fruits were conducted. The results showed that the yield is strongly correlated with fertilization of DAP, but no effect was detected on the P concentration of fruits. Export of P by fruits was also variable and is not clear linked with increasing fertilizer doses. Values, despite their weakness, appear in the standards, compared to results from other regions. The conclusion is that the yield responded more to increasing the contribution of nitrogen to that of phosphorus. P, initially abundant in the soil by precedent fertilizations, had no detectable effect on production. Fertilization of the crop should be balanced by reducing phosphorus doses to the just annual crop needs and incorporating nitrogen and potassium fertilizers.