Cumulative and Residual Effects of Organic and Chemical Fertilizers on Chemical Properties and P Sorption-Desorption Reactions in a Calcareous Soil: II. Phosphorus Desorption Kinetics

The kinetics of phosphorus (P) desorption in soils is important from plant nutrition and environmental perspectives. An experiment was conducted on the field plots that received 100 t ha of solid dairy manure 1 (DM), sewage sludge (SS), or urban solid waste compost (UC) and one rate of chemical fertilizer (CF) for 1, 3 or 5 consecutive years to investigate the residual and cumulative effects of organic and chemical fertilizers on kinetics of P release. The kinetic data was best described by parabolic diffusion equation as evidenced by the relatively higher values of determination coefficient (R ). Application of both chemical and organic fertilizers 2 increased the values of P diffusion coefficients of soils (R), the initial (Dr ) and final (Dr ) P release rate indices in f and the values of P release rate constants (a and b) obtained from the power function equation as compared to the control (C). The largest residual and cumulative effects of treatments on the above parameters were also observed in the plots received SS and DM, respectively. Application of both chemical and organic fertilizers decreased 1/ constant as compared to the control. Adding DM and SS to soil increased the quantity of soil desorbable P after 0.25 (Q ) and 72 h (Q ). With the exception of a, that did not show significant relationships in f with calcium carbonate equivalent (CCE), the CCE content was positively correlated with the other rate and quantity parameters. The organic carbon (OC) content showed close relationships with Q , Q , Dr , Dr and R in f in f parameters.