Using Double Function Solubility Diagram to Study the Effect of Phosphorus Fertilizer on the Availability of Phosphorus in Different Soil Orders.


A pot experiment was carried out during autumn growing season of 2016-2017 at the Gerdarasha field of College of Agriculture Engineering Sciences, to study the effect of three dominant soil orders (Mollisols (M), Vertisols (V) and Aridisols (A)), five levels of applied phosphorus fertilizer (0, 80, 160, 240 and 320 kg TSP ha-1) and combination between them on the availability of phosphorus (P) using solubility diagram at booting stage and wheat yield. The factorial experiment was depended using a completely randomized design (CRD) with three replicates. The results indicated that the soil orders were affected the phosphorus status. It appears that the soil order studied was plotted between di calcium phosphate DCP and octa calcium phosphate OCP. The phosphorus availability of the studied soil orders can followed the following series Mollisols (M) > Vertisols (V) > Aridisols (A). The application of phosphorus caused an increase in phosphorus availability or caused shifting the treatments towards the more soluble forms of phosphorus Di calcium phosphate di hydrate ( DCPD). The combination of soil orders and levels of applied phosphorus also influenced on phosphorus status. The application of 320 kg.ha-1 of triple superphosphate to the Mollisols soil increased the phosphorus status toward the plotted between DCP and DCPD which were the most soluble forms of phosphorus in the phosphorus solubility diagram, which recorded the highest wheat yield (3.66) Mg ha-1 in combination treatment (Mollisols-TSP320). While the lowest grain yield (2.06) Mg ha-1 was obtain from (Aridisol-TSP0) since this combination treatment was plotted between TCP and OCP or non-soluble and low soluble P-compounds.