Effect of different types and levels of phosphorous fertilizers on kinetics of phosphorous release in the soil

A field experiment was carried out in one of the fields of Diwaniya governorate for the agricultural season 2019 to study the effect of adding organic fertilizer and sources of phosphate fertilizer during the growth stages of the maize plant (Zea mays. L) and its reflectance on growth and productivity of the plant. The experiment was conducted according to the design of the (split-split plots and included two levels of the organic fertilizer(L1-L0) standing for (0- 1.5 tons) and three sources of the following fertilizers: Tri super phosphate TSP, DiAmmonium phosphate DAP and Urea UP) as add to control treatment (p0) symbolized by p1, p2, p3, respectively. The seeds of maize (Zea mays. L) Behoth 5018s cultivar were planted in a 25 kg/H range. The kinetics of phosphorous in the soil were studied. The phosphorus release rate was determined during the stages of plant growth, and the best equation in describing the mechanism of desorption in the stages of plant growth (25, 50, 75, 100 and 125 days). The results showed that all used equations (first-order, diffusion and Elovich) have described the mechanism of phosphorous release from a solid phase to the soil solution. All equations gave a highly significant correlation (r) between released phosphorous in the stages of Plant growth. The first-order equation surpassed other equations describing the mechanism of phosphorous release in the soil. The values of the coefficient of phosphorous release rate (KP) ranged between (0.0045 - 0.004 mg. p. kg-1 . Day-1 ) for the equation of first- -order, where the results showed that the linear relationship between the amount of released phosphorous as a function of time for the equation of first-order, is the best equation in describing the release, which indicates the interest in the amount and timing of addition of p fertilizers during the stages of plant growth, according to what was shown in the kinetic equations. Keywords: Phosphorous desorption, fertilizers, maize, kinetic equations, soil solution.