Soil extractable P, Fe and Zn as affected by suspension and granule form of phosphate fertilizer

To compare the effect of liquid and solid forms of P-fertilizers on plant available P, an experiment was conducted on two calcareous soils. A granule or the same amount of suspension was added to soil samples. Also in another treatment, H2SO4 was added to suspension to evaluate its effect on increasing soil available P. Soil available P was determined after 14, 36 and 165 days. After 14 days and in soil sample 1, acids suspension fertilizer caused about 30 percent more available P than granule treatment but the effectiveness of suspension was the same as granule. In soil sample 2 and after 14 days, there was no difference between fertilizers. After 36 days, granule fertilizer caused about 120 and 40% more available P in soil samples 1 and 2 respectively. After 165 days available P in soil samples 1 and 2 were about 450% and 130% higher compare to suspension. Also Results indicatedthe shape of the fertilizer had no effect on the soil available Fe and Zn. It is concluded that if plant could be able to absorb P from soil in a short period of time after fertilizer application, granule P fertilizer can replace by the same amount of suspension. If not, more suspension fertilizer is needed.