FORECASTING BY LABORATORY TESTS OF NITROGEN LEACHED AND ABSORBED IN SOIL-PLANT SYSTEM WITH UREA-BASED CONTROLLED-RELEASE FERTILIZERS COATEDWITH LIGNIN

In order to predict release of nitrogen (N) from controlled-release fe rtilizers (CRF) from laboratory experiments, new types of lignin-coate d fertilizers were studied. Laboratory methods were 1) release of urea into water and 2) an extraction procedure using an electroultrafiltra tion technique (EUF). The results of these two methods were compared t o the amount of N released in a vegetation experiment in the greenhous e. The results showed a good relationship between the two laboratory m ethods. The correlation coefficient between the rate constant K determ ined in the water extract and each of the N-fractions was highly signi ficant. The total amount of N released in the vegetation experiment wa s correlated to parameters of the laboratory methods. The N uptake by the plant was significantly correlated with the first order constant a nd with the fertilizer's EUF-NII index. The N leached was also correla ted with the EUF-NI and EUF-N (I+II) indices.