L. Garcia et al., COATED DIAMMONIUM PHOSPHATE EFFECT ON SOIL-NITROGEN LIXIVIATION AND ITS RELATION WITH PROPERTIES KINETICS, Communications in soil science and plant analysis, 26(19-20), 1995, pp. 3405-3416
Slow-release fertilizers were prepared by coating diammonium phosphate
(DAP) with rosin and tricalcium phosphate. The DAP dissolution kineti
cs in water of these products is of the Ist order, leading to the conc
lusion that the values of the dissolution rate constants depend on the
coating percentage. A glasshouse test with rye grass was carried out
in order to evaluate the efficiency of the fertilizers as regards nitr
ogen (N) uptake by the plant and N lixiviation in high leaching condit
ions. It has been proved that by using coated products the loss of N w
as reduced, but the yields of dry matter were still good as was the N
uptake by the plant. It has also been proved that losses through lixiv
iation are lower when the fertilizers are mixed with the soil. Finally
it was possible to establish linear correlations between kinetic indi
ces deduced from the solubility of the products in water and indices d
educed from the response of the soil-plant system.