Wednesday, November 15, 2006 - 9:15 AM
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Nutrient Dynamics in an Intensively Managed Grassland on Peat Soil in The Netherlands.

Christy van Beek1, Gé Van den Eertwegh2, Gerard Velthof1, and Oene Oenema1. (1) Alterra, PO Box 47, Wageningen, 6700 AA, Netherlands, (2) WS Rivierenland, Prinses Beatrixlaan 25, Tiel, 4000 AN, Netherlands

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.