RESULTS OF LYSIMETER EXPERIMENTS ON THE E FFECT OF DCD AND CMP

Results are reported of studies into the nitrification inhibitors DCD (dicyandiamide) and CMP (1-carbamoyl-3(5)-methylpyrazole) made in the frame of a complex lysimeter experiment. The aim was to optimize manag ement of drinking water protection areas. In a crop rotation comprisin g cereals and root crops, DCD shall only be used in combination with s lurry application in autumn. In spring, DCD can be applied together wi th slurry dilution. This procedure, however, might not in any case red uce N leaching. Combined application of DCD (to slurry in autumn) and CMP (to mineral fertilization) is not recommended for economic reasons . Application of CMP together with the normal mineral fertilizer rate in an cereal-forage crop rotation is disapproved either. The use of ni trification inhibitors requires an improved soil monitoring system.