1. Introduction
Forage and ruminant production in Western Europe have increased significantly since World
War II under, on the one hand, the influence of the Common Agricultural Policy of the European
Union that guaranteed high and stable product prices De Wit et al., 1987; De Wit, 1988 and on
the other, relatively low prices of inputs, particu- larly inorganic fertilizers and concentrates Kete-
laars
and van
der Meer,
1998. Inorganic
fertilizers are, in general, a more reliable and easier-to-manage source of nutrients than either
legumes or animal slurries, while concentrates serve as a ready means to supplement the unpre-
dictable quantity and quality of roughage supply and allow intake levels necessary to sustain high
levels of production per animal.
Dairy farming is the major sector of Dutch agriculture, using about 64 of the cultivated
area and serving as the main source of income for about 35 of the farmers CBS, 1998. In the
sixties and seventies these dairy farming systems strongly specialised and intensified by increased
inputs of chemical fertilisers and purchased feeds. Although introduction of the milk quota system
in 1984 reduced milk production by 15 the average is still high, i.e. between 1987 and 1997
about 12 250 kgha on the specialised dairy farms. Especially, systems in the sandy regions in
the East and South of the Netherlands are inten- sive, mainly because of the high prices of agricul-
tural land. In the last decade the livestock production sec-
tor has come under increasing pressure as the European Union introduced the milk quota sys-
tem, effectively curbing total national and individ- ual
farm production
volume, and
national governments increasingly took measures to reduce
the losses of nutrients from these systems to the environment Van Boheemen, 1987; Schro¨der,
1992; van der Meer et al., 1997. Intensification has led to a serious imbalance between inputs of
nutrients in purchased fertilisers, concentrates and roughage and atmospheric deposition, and out-
puts in milk and meat, as illustrated in Table 1 for nitrogen at the national level in the Netherlands.
At farm level for the period 1983 – 1986 outputs were on average only 14 of the input for nitro-
gen N, 32 for phosphorus P and 17 for potassium K.
So far most attention has been paid to pollu- tion of water and soil resources by leaching and
run-off of N, P and organic matter and accumula- tion of phosphorus. The N surplus contributes to
environmental pollution
through ammonia
volatilisation, run off, leaching of nitrate and production of N
2
O during denitrification Aarts et al., 1992. Ammonia volatilization has received
particular attention in areas with high animal densities, where it contributes to high levels of
atmospheric deposition. This high N-load causes eutrophication of terrestrial ecosystems, increased
susceptibility of trees to stress, soil acidification and excessive nitrate leaching from affected
ecosystems van der Meer et al., 1997.
Table 1 Nitrogen balance of the Dutch dairy farming sector 10
6
kg
a
Year Imports
Exports Surplus
NUE
b
Fertilizer Concentrates
MilkMeat 42
36 8
70 1950
0.46 138
1960 25
45 118
0.28 1970
277 52
56 273
0.17 1980
356 117
77 396
0.16 379
153 1985
83 449
0.16 351
303 0.20
138 90
1989
a
Source: van der Meer et al. 1997.
b
NUE, nitrogen use efficiency: total outputtotal input.
Table 2 Maximum levy-free see text for explanation nutrient sur-
pluses in the Netherlands kgha, deposition and fixation by clover not included
2000 2002
2005 2008
1998 N
Grassland 300
275 250
200 180
150 125
110 175
100 Arable land
P 15
13 17
11 Grassland
9 15
13 Arable land
11 17
9
for farming systems were defined Table 2. These threshold values are temporary political com-
promises between environmental demands and agricultural
possibilities Dekker
and van
Leeuwen, 1998. Surpluses above the levels presented in Table 2
will be levied. However, uncertainty exists among dairy farmers on the impact of a reduced surplus
of P through lower inputs of fertilizer or concen- trates on soil fertility and — as a consequence
— on crop production. Moreover, reducing the P surplus may lead to high costs because it limits
the application of slurry, which then has to be exported or additional land has to be bought.
This legislation stimulates more efficient nutrient management as farmers try to avoid fines while
maintaining production.
These measures have resulted in reduction in the surpluses on commercial farms Aarts et al.,
1999, but further reductions are necessary. One of the goals of agricultural research is to
develop guidelines for farmers to design and im- prove their farms, taking into account their spe-
cific circumstances such as soil type, and both short- and long-term objectives. In addition, the
government needs information on the practical feasibility of measures aimed at reducing the envi-
ronmental impact of dairy farming. This paper describes the results of farming systems research
focusing on dairy farming on sandy soils and long-term objectives with respect to nutrient sur-
pluses, and, hence on improving nutrient manage- ment.
2. Objective dairy farming system ‘De Marke’
Kategori