The effect of straw and monolinuron application on the fate of 15 N‐urea in lysimeters

The influence of herbicide application (monolinuron) and manuring with straw on the fate of urea 15 N was studied in two soil types. The major loss of urea N applied to soil can be considered as denitrification rather than downward migration (leaching). This loss was higher in the loess than in the sandy soil; incorporation of straw slightly increased the loss, whereas addition of monolinuron decreased it. The labelled urea 15 N was better utilized by plants in the sandy than in the loess soil. During the first year after using straw in loess the N uptake by plants significantly decreased. Addition of monolinuron did not change the utilization of urea‐ N . In the second year there was only little utilization of the N residues by barley. The highest fertilizer N residues were found in soil that had been treated with straw. A slight increase of residual fertilizer N was also observed in the monolinuron‐treated soil. The amount of residual fertilizer N in the non‐treated soils was similar in the sandy and the loess soil.