grated effect of processes is illustrated and the transfer of the knowledge acquired is facilitated as
the functioning of the system can be directly observed. By building a bridge between theory
and experimental testing the danger is avoided that, as in desk-studies, too much attention is paid
to elements that appear less relevant in practice or — the other way around — that insufficient
attention is paid to issues that prove important later. Prototyping also has some disadvantages.
The experimental system has been selected, rather subjectively, from a number of options and reli-
able comparison with other systems is impossible, since only one system can be implemented and
even that system is continuously developing. Therefore, the results can not be tested statisti-
cally. These disadvantages can at least partly be overcome by: i using an appropriate monitoring
programme, ii additional interdisciplinary re- search aimed at determination of causal relation-
ships that explain the behaviour of the system and can be used to investigate the consequences of
alternatives, and iii combine the experimental research at the prototype farm with modelling to
explore alternative possibilities Van de Ven and van Keulen, 1996. Prototyping is also expensive:
Implementation of the experimental system at ‘De Marke’ required an investment of 10 million
guilders and the annual budget amounts to about 1 million guilders.
3
.
2
. Experimental methods For grass cut for conservation, silage maize and
beets, dry matter yield was determined on the weighing bridge. It has been assumed that during
conservation and feeding an additional 7 is lost. Intake of pasture grass has been estimated by
visually estimating standing dry matter at the beginning and the end of the grazing period and
assuming a daily growth rate of 50 kg dry matter ha.
The quantities of N and P in faeces produced in the stable have been determined as volume times
contents. The quantities in faeces and urine ex- creted during grazing have been estimated from
the input in fodder by subtracting the output in milk and meat and the production in the stable.
This calculation procedure may lead to relatively large inaccuracies in the partitioning of nutrients
between stable and pasture.
4. Experimental farm ‘De Marke’
To test the selected farming system 55 ha of land were bought in De Achterhoek, the eastern
sandy part of The Netherlands. Hence, the exper- imental farm is almost twice the size of the aver-
age farm in the sandy area. This was considered necessary for research reasons: to obtain suffi-
ciently reliable results more animals are needed than on the average farm.
The land comprising the experimental farm ‘De Marke’, reclaimed from heather around the turn
of last century, consists of an upper layer of 25 – 30 cm with an average organic matter content
of 4.9, overlying practically humusless sand. The groundwater table is at most places too deep
for water to reach the root zone. The water holding capacity is, therefore, less than 50 mm on
60 of the cultivated land and for the remainder varies between 50 and 100 mm. Hence, the land
belongs to the driest 10 of the sandy soils in the country.
The plots of ‘De Marke’, acquired from various landowners, had a different history with respect to
the application of animal manure, resulting in considerable differences in soil fertility, especially
for phosphorus Schoumans, 1995.
The total land area comprises the ‘home plot’, close to the farm buildings, that can be irrigated,
if necessary, and is preferentially used for grazing, and the ‘field plot’ more distant, with no irriga-
tion possibilities and mainly used for silage making.
The farming system of ‘De Marke’ operates through very careful management of crops, live-
stock and manure.
4
.
1
. Crops ’De Marke’ consists of 31 ha of grassland and
24 ha of maize until 1995 18 ha and 6 ha of fodder beets. About one third of the grassland is
permanent, the remainder in rotation with maize.
Most of the maize is used as whole crop silage and about 10 ha for ground ear silage home-
grown concentrate. Annual N application avail- able N in the slurry + fertiliser-N does not exceed
250 kgha on grass and 100 kgha on maize. Actual rates of application take into account
residual effects of preceding crops, particularly ploughing-in a grass sward or a cover crop. Maize
is always followed by a cover crop to absorb residual inorganic N. In recent years no fertiliser
P has been applied. Irrigation is applied only to enable grazing during part of the day because of
reasons of animal welfare or to prevent early dying of crops due to drought.
4
.
2
. Li6estock Milk production per cow is high at 8150 kg per
lactation, with almost 4.5 fat and 3.5 protein. Young stock is kept only for replacement. This
explains the low N and P output in animals sold compared to the current farm. Much attention is
paid to avoid protein and P surpluses in the ration of the cows. Grazing is restricted, particu-
larly in late summer and autumn to avoid large N losses from urine patches. From April to Septem-
ber cows are stabled during part of the afternoon and at night, and supplemented with maize silage.
4
.
3
. Animal manure ’De Marke’ has a free-stall barn, with a closed
coated floor, sloping towards a central longitudi- nal urine drain. Alleys are equipped with a
scraper to remove faeces and urine to a com- pletely enclosed storage silo. All slurry produced
is applied to the farm; on grassland by injection with open slits between early March and 15 Au-
gust, and on maize land by injection just before sowing.
The main characteristics of the experimental farming system are summarized in Tables 3 and 4.
A comparison is being made between the expected values of these characteristics prognosis — the
Table 3 N and P balances of the average specialized dairy farm in the middle of the eighties, the prognoses at the start of ‘De Marke’ and
the values realized in the years 19931994 and 19941995 kgha ‘Average’ 19831986
Characteristic ‘De Marke’ prognoses
19931994 19941995
N P
N P
N P
N P
Input 67
6.0 52
1.8 Fertilizer
96 330
0.0 15.0
41 5.9
82 15.0
Feed 84
182 11.5
32.0 0.9
49 0.9
49 0.9
Deposition 49
1.0 49
30 0.0
12 0.0
5 0.0
N-fixation clover 0.0
7 0.0
5 0.0
Various 4
0.0 4
0.0 48.0
12.4 238
17.7 568
199 Sum
12.8 192
Output 68
12.0 Milk
62 10.6
65 10.5
64 10.6
8 2.2
Meat 10
13 3.0
9 2.7
4.0 0.0
0.0 Feed
8 1.2
0.0 Mutation
0.0 0.0
Number of animals 0.2
− 0.1
0.0 −
6.4 Manure storage
− 50
− 1.0
11 0.0
0.8 17
− 2.3
− 35
Feed stock 0.0
0.0 Sum
16.0 81
70 7.6
40 11.6
59 12.8
Input–output
a
198 6.1
140 0.0
122 32.0
4.8 487
a
Accumulation in soil and losses to air and groundwater.
Table 4 Characteristics of the cattle component of the average specialized dairy farm in the middle of the eighties, the prognoses at the start
of ‘De Marke’ and the characteristics realized in the years 19931994 and 19941995 ‘De Marke’
‘Average’ 19831986 Characteristic
19931994 199495
prognoses 11 890
Realized milk production kgha 12 047
12 798 11 664
12 487 12 681
13 161 FPCM
a
kgha 12 288
2.31 Milking cowsha
1.47 1.45
1.43 8495
FPCMcow kg 8720
5697 8467
0.57 0.81
0.76 Young stockcow
0.70 4047
Purchased concentrate kg DMha 1377
1544 1542
251 Purchase of roughage kg DMha
2136 693
11 240 12 726
16 158 Feed intake cattle kg DMha
11 495 1.23
Feed intake cattle kg DMkg FPCM 0.90
1.00 0.94
Nutrients kgha N
P N
P N
P N
P Input
74.0 278
40.1 336
Feed 47.1
496 330
43.6 Output
12.0 62
10.6 65
10.5 64
10.6 Milk
68 4.0
8 2.2
10 13
3.0 Meat
9 2.7
Mutation cattle 0.0
0.0 0.2
- 0.1 Input–output
58.0 = Faeces+urine
208 415
27.3 261
33.4 257
30.6
a
Fat and protein corrected milk.
and 0 kg P, respectively. The N surplus in the year 19931994 140 kg Nha was close to the expected
value, but it was clearly higher 198 kg Nha in the subsequent year, due to a higher fertilizer
application rate and the reduction in stocks of slurry. The P surplus exceeded the expected value
in both years, but if the changes in stocks of slurry are disregarded it is slightly negative in
19941995, i.e. slightly more P was exported from the farm in milk and cattle than imported in
fertilizers and feed. As the import of P in feed appeared higher than expected application of fer-
tilizer P was discontinued from the spring of 1994 onwards. Because of autonomous developments
especially legislation on low-emission application techniques and increasing milk productioncow
N surplus at the current farm has decreased by about 80 kgha 17 to about 400 kgha Van
Eck, 1995, while the P surplus was hardly af- fected 30 kgha; Oenema and van Dijk, 1994.
results of the model calculations at the basis of the farming system design — and the results
realized in the financial, 1 May to 1 May years 19931994 and 19941995, the first two years that
the system functioned completely. The ‘average’ farm from the middle of the eighties is taken as
reference henceforth referred to as ‘the current farm’ as a discontinuity occurred at that time,
because of the introduction of milk quota and of environmental legislation.
5. Results
