Kinetic of phosphate release in soils has drown a co siderable
attention in recent years. Soluble organic matter plays an important part in
phosphate release. Effect of fulvic acid (FA) on phophate desor tion was
investigated. Results reve~led that power function (modified Freun lich), two
sities and zero-order kinetic equations gave a highly significant (R2) mostly in
all cases in different treatments of monoca/cium phosphate (MCP) and (FA)
treated soils. It was observed that rate coefficients of phophate desorption
(Kd) in sandy soil were gradually increased with P.fertilizer added as
compared with other treatments. Results also revealed that application of
fulvic acid to soil decreased the P-desorption particularly in alluvial soil. FuMc
acid treated soil resulted in a reduction of P-desorption and also reg lated the
releaseable fraction of phophorus in soils. It was noticed that for he entire
reaction period, alluvial clay soil can be able to supply P to cultivated media
as compared with other investigated soils. Results also showed that the
supplying power of FA treated soils was almost emphasized over the
uncoated SP treated soils. These result may be related to the role of FA for
increasing the supplying power due to chelation reaction.