The study of interaction air filled porosity and the use of urea and mono calcium phosphate on the availability of nitrogen, phosphorus and potassium in incubation period

Air filled porosity as one of the most important properties of the soil, can influence the availability of water, oxygen, and other nutrient elements. In order to investigate the interactions between air filled porosity levels and urea and phosphorus fertilizers it was done on availability of macro elements (N-NO3, P, K). A factorial experiment was carried out based on the randomized completely design with two factors including air filled porosity at seven levels (0, 4, 8, 12, 16, 20, 24%), and fertilizer at two levels (control and optimum level) from mono calcium phosphates and urea sources in the incubation period in three times (40, 80, 120 days) at three replications. Some of the chemical characteristics of treated soils such as pH, concentration of bicarbonate (HCO-3) and nitrate ions, and available phosphorus and potassium at different levels of air filled porosity were measured. Results showed that the correlation between pH, nitrate, bicarbonate, phosphorus and potassium with air filled porosity changes was significant. Increasing the incubation time was caused to reduce the amount of availability nitrate, phosphorus and potassium soil. Also with decreasing air filled porosity levels pH, HCO-3 concentration and availability of phosphorus were increased. The concentration of nitrate ions under the influence of temperature, pH, moisture and oxygen in different of the air porosity levels (12, 16 and 20%) showed a significant increase. So the air filled porosity of 12, 16 and 20 percent were determined the optimal range for the concentration of nitrate, phosphorus and potassium available