From 1999 until 2002 fluxes and transformations of N and P were measured in an intensively managed grassland on peat soil with shallow (~ 40 cm) groundwater level. Measurements included inputs of N and P via fertilizer and animal manure, outputs via  herbage, denitrification, mineralization, discharge, run-off, and concentrations of N, P and Cl in the soil solution at various places accros the field. The soil consisted of a man-made topsoil of about 30 cm, oxidized eutrophic peat (0.3-1 m), reduced eutrophic peat (1-3 m), calcareous marine deposits containing light and heavy clay (3 – 9 m) and Pleistocene sands (> 9 m). The presence of the eutrophic peat layer had a distinct impact on the nutrient dynamics of the peat soil, i.e. it largely governed the composition of the soil solution and was a considerable contributor of nutrient leaching to the adjacent surface water (Table 1).

Table 1. Average fluxes (kg ha^-1y^-1) in an intensively managed peat soil in The Netherlands (2002). Contributions of each flux to the N and P loading of surface water are shown in brackets (%).

		N	P	Cl
IN	Mineral ferilizer	159 (17-20)	0	11
	Atmospheric deposition	31 (8-9)		71
	Slurry application	159 (17-20)	22 (22-34)	81
	Dung and urine of grazing animals	87 (911)	9 (9-14)	33
	Supply from peat layer	8 (8-27)	3 (33-82)	120
	Mineralization of soil organic matter	210 (17-31)	10 (2-14)	<1
OUT	Mown grass	-231	-24	-79
	Grazing	-100	-10	-79
	Denitrification	-210	0	0
	NH3 volatilization	-20	0	0
	Leaching to surface water	-38	-6	-170
	Groundwater recharge	-4	-0.4	<1
SUM		51	4	-12

The presence of shallow groundwater and eutrophic peat facilitate large biochemical processes (mineralization, nitrification and denitrification) and thereby veile direct relations between agricultural management and surface water quality.