In order to predict release of nitrogen (N) from controlled‐release fertilizers (CRF) from laboratory experiments, new types of lignin‐coated fertilizers were studied. Laboratory methods were 1) release of urea into water and 2) an extraction procedure using an electroultrafiltration technique (EUF). The results of these two methods were compared to the amount of N released in a vegetation experiment in the greenhouse. The results showed a good relationship between the two laboratory methods. The correlation coefficient between the rate constant K determined in the water extract and each of the N‐fractions was highly significant. The total amount of N released in the vegetation experiment was correlated to parameters of the laboratory methods. The N uptake by the plant was significantly correlated with the first order constant and with the fertilizer's EUF‐NII index. The N leached was also correlated with the EUF‐NI and EUF‐N (I+II) indices.