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
5
.
1
. The farm system The N and P balances of the farm are presented
in Table 3. The prognosis was that the surplus at farm level would decrease from 487 kg N and 32
kg Pha surpluses at current farms to 122 kg N
5
.
2
. The cattle component The milk quota of ‘De Marke’ was slightly
lower than that of the current farm, but reduc- tions in the second half of the eighties have re-
sulted in comparable quota during the reporting period. Model calculations Table 4 suggest that
the feed requirements for a given milk quota decrease when milk production per cow increases,
as per kg of milk less energy is needed for mainte- nance of the animals and less young stock is
needed for replacement at a similar life span. Hence, the aim at ‘De Marke’ was to realize a
considerably higher milk production per cow than the current farm, which was realized and has
resulted in a much lower stocking rate. The higher milk production has not resulted in the expected
savings in feed. The energy intake kVEM kVEM is the abbreviation of the Dutch kilo digestible
energy for milk production Tamminga et al., 1994 of the dairy cattle appeared substantially
higher than expected on the basis of the feeding standards, without the animals showing signs of
fattening Meijer, 1994. The models were origi- nally developed for a production range up to
about 6500 kgcow personal communication, A. Meijer, Experimental Station for Cattle, Sheep
and Horse Husbandry PR, and it appears, therefore, that extrapolation to the realized levels
at ‘De Marke’ is not without problems.
The number of young stock per milking cow was higher than anticipated and, on average,
practically similar to that on the current farm. The main reason is that in the reported period the
herd was in its building-up phase, requiring maxi- mum possibilities for selection. In practice, in the
sandy areas, the number of young stock per milk- ing cow increased to 1 Leneman et al., 1999,
while at ‘De Marke’ it has decreased to 0.7. Because of the high energy requirements of the
dairy cattle and the high number of young stock, dry matter intake per unit of milk production
during the first year was 11 higher than pre- dicted, but considerably below that at the current
farm. In the second year it was only 4 higher than predicted.
In formulating the ration, including grazing management, the aim is to minimize its protein
and phosphorus contents. At ‘De Marke’ animals are taken out of pasture about 1 month earlier
than at the current farm and daily grazing time is restricted. In summer the cows are stabled during
the afternoon and the night and are supplemented with maize. In the first year the cows were stabled
at night only, but the alternate periods of availability of protein-rich daytime grazing and
protein-poor maize at night feed appeared too long and led to digestive problems in the highly
productive cattle. The dairy cows are moved to a new plot every 2 days, after which the pasture is
further grazed by young stock. Restricting grazing time results in less urine and manure patches, and
in a larger part of the faeces and urine being produced in the stable. Nutrients are thus utilized
much more efficiently, as less N is lost from pasture, and application of slurry is synchronized
to crop demand.
As manure is spread on the land only between early March and mid-August, the required storage
capacity at ‘De Marke’ is substantially higher than at the current farm, that did not face any
restrictions on manure application in the middle of the eighties. However, the time during which
manure can be spread on sandy soils has been limited by legislation to the period 1 February – 15
September, hence the storage capacity at the cur- rent farm has also increased.
The difference between input and output in Table 4 represents excretion by the animals. At
the current farm it exceeded 400 kg Nha, indicat- ing that only 16 of the N consumed by the
animals was converted into milk and meat. The anticipated reduction at ‘De Marke’ 50 was
based on increased utilization efficiency at animal level to 25 through a low-protein ration, high
milk production per cow and a reduction in the number of young stock. The realized utilization
efficiency of feed N was 22 due to the higher protein content in the ration — protein intake
exceeded the value expected on the basis of the CVB-standards Meijer, 1994 by more than 18
— and a higher number of young stock. P-utiliza- tion efficiency was also lower than expected, but
the difference was smaller than for N.
5
.
3
. The manure component Manure production at pasture was in agree-
ment with the prognosis Table 5 and nutrients in faeces and urine produced in excess of what was
anticipated appear to have ended up in the stable. By restricting grazing time to about one third of
current assuming day-and-night grazing excre- tion of nutrients at pasture was on average only
22 N and 17 P of the total, compared to 50 at the current farm. In the eighties, on a substan-
tial part of the farms, dairy cattle were stabled during the night so that, on average, a smaller
part of the nutrients in faeces and urine than given in Table 5, will have been excreted at pas-
ture. Presently, on more than half of the farms on sandy soils dairy cattle are stabled at night.
The difference between input and output of nitrogen in the manure represents volatilization of
ammonia from the stable, at pasture, during stor- age and following application. Ammonia emission
had to be estimated as it was not measured at ‘De Marke’ during the period treated here, so that the
results of the model, in relative terms, are repro- duced. In absolute terms the losses were 3 – 4
kgha higher as more nitrogen was excreted by the animals. As at the current farm N-excretion is
much higher and manure was surface-applied, N-loss as ammonia was 105 kgha. Due to the
compulsory injection of manure, ammonia emis- sion at current farms will have decreased at this
moment by about 40 kg Nha Lekkerkerk et al., 1995. Of the total loss of more than 20 kg Nha
– from faeces and urine — 4 kg was lost during grazing volatilization 7.5 of the N-excretion,
Vertregt and Rutgers 1988, 4 kg following ap- plication at pasture 5 of the ammonia-N, 0 kg
after injection on arable land 1.25 of the am- monia-N and 14 kg from the stable 7 of the
N-excretion, which was, therefore, the main source of ammonia. Ketelaars et al., 1995. At
the moment, as more measured data for ‘De Marke’ are available, the impression is that, even
under careful management, volatilization losses are somewhat higher than assumed here Van der
Schans et al., 1999.
5
.
4
. The soilcrop component The area of the different forage crops is deter-
mined on the basis of a compromise between the production capacity of the crops under the condi-
tions of ‘De Marke’, the value of their products in the ration and the possibilities to use animal
manure efficiently.
The proportion of grass in the rotation at ‘De Marke’ is lower than at the current farm and the
proportion of maize consequently higher Table 6. The main reason is the aim to reduce output of
N in urine and faeces, demanding energy-rich feed
Table 5 Nutrient flows of the manure component for 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 ‘De Marke’
‘Average’ 19831986 19931994
Characteristic 19941995
prognoses N
P N
P N
P N
P Input
55 7.0
52 26.0
7.7 191
62 3.3
Production faeces and urine at pasture Production faeces and urine in the stable
224 32.0
151 20.2
209 24.7
194 27.1
Output 164
26.0 51
7.0 48
7.7 57
Faeces+urine at pasture after volatilization 3.3
33.5 227
25.8 181
20.2 Applied slurry after volatilization
137 32.0
146 −
6.4 Change in manure stock
11 −
1.0 −
50 Input–output
− 0.1
21 18
0.0 105
0.0 = Ammonia from manure
22
Table 6 Characteristics of the crop component 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 ‘De Marke’ prognoses
19931994 19941995
Characteristic ‘Average’ 19831986
Area of total
56 55
60 Grassland
90 33
34 10
32 Maize
11 11
8 Fodder beets
Artificial fertilizer kgha
67 52
96 N
331 6
2 15
P 25
38 K
30 30
12 N-fixation clover kgha
5 Net yield
kg DMha
a
9276 9409
9942 8792
Grass Maize
11 167 10 274
10 657 9276
14 133 16 583
– 10 064
Beets leaf included 10 436
10 615 Average of farm
9046 9975
a
Net yield is the value after subtraction of grazing, harvesting, conservation and feeding losses, and thus equals animal intake.
with a low N content, to compensate for the high nitrogen contents in the grass products in the
ration. Supplementary feeding with maize serves as an energy buffer and, moreover, limits the risk
of grass tetany during the grazing season. Maize silage has a higher energy content than grass
silage, reducing the need for concentrate supple- ment in the winter period. Moreover, maize and
fodder beets are much more efficient in terms of water and nutrient requirements per unit har-
vestable dry matter than grass Aarts and Grashoff,
1993. At
‘De Marke’
moisture availability is generally the most limiting factor
for crop production and although the aim is to minimize
water use
for irrigation,
because groundwater is a scarce resource, and because it
requires energy and labour, the area of grassland exceeds that of arable land. Important reasons are
the higher yields of N and P reducing import of these elements in purchased feeds, the possibili-
ties for grazing and the greater opportunities to use animal manure. Moreover, grassland stimu-
lates soil organic matter build-up and, therefore, indirectly soil moisture supply. In recent years the
proportion of maize in the rotation at current farms has also increased in 199293 it comprised
about 25 of the area at dairy farms in the sandy areas Leneman et al., 1999 and the situation at
‘De Marke’ is not an exception anymore. Fodder beets are hardly grown in actual prac-
tice, but at ‘De Marke’ they were intended to replace part of the concentrates. Moreover, the
yield of dry matter and energy per hectare is as a rule very high, and its nitrogen uptake capacity
exceeds that of maize, so that beets as first crop after the grassland period was considered safer.
As large amounts of beets in the ration for highly productive dairy cattle appeared to lead to diges-
tive problems, after the first year the proportion of beets in the ration in winter was reduced, and
part of the beets was ensiled with maize, so that they could be incorporated in the summer ration.
However, the beets then have to be harvested early, hence at a lower dry matter yield, and
cultivation of a catch crop is necessary to take up the nitrogen mineralized after harvest. Despite
incorporation of the beets in the summer ration the original area of beets 6 ha appeared too
large for judicious feeding practice, and was re- duced to 4 ha in 1994, and eventually discarded
after 1995.
At ‘De Marke’ part of the maize is harvested as ground ear silage GES, very high in energy and
mainly used as concentrate replacer for the most
productive animals. Maize stover is also harvested and used as an absorbing bottom layer for the
rather wet grass silage in autumn, which is then covered with beet leaves. This silage appeared
very suitable for feeding young stock and dry cows. In current practice GES is also increasingly
used, but the stover is not yet harvested, and less autumn grass is ensiled, as grazing generally con-
tinues for 1 month longer.
The total grassland area is divided into 22 ha for ley farming and 9 ha for permanent pasture.
Continuous arable farming leads to lower soil organic matter content than ley farming, eventu-
ally resulting in increased drought sensitivity. Yield of maize under ley farming is higher than
under continuous cropping and the risk of build- up of weed populations by selection or building
up of resistance is lower. Moreover, during the grass period herbicides, used on the arable crops,
can be decomposed. Grassclover mixtures were always sown immediately after harvest of the
maize, hence clover entered the winter period in the seedling stage and appeared very sensitive to
frost, leading to low clover densities after most winters. Consequently, nitrogen fixation by clover
in grassland, calculated as 4.5 of clover dry matter yield Biewinga et al., 1992, was substan-
tially lower than expected. Sowing in spring may help to avoid this problem. The grass sward, after
3 years, is broken up in early spring. Subse- quently, fodder beets are grown — because they
can use the nitrogen mineralized from the decom- posing grass very efficiently — followed by two
home plot or four field plot years of maize. Additional research at ‘De Marke’ has shown that
cultivation of maize after 3 years of grass is also possible when no artificial fertilizer is applied:
mineral nitrogen in the soil did not reach alarm- ingly high levels, and the quality of the groundwa-
ter was no different from that under other plots.
Fertilizer application is plot-specific and based on the uptake capacity of the crops, taking into
account soil moisture supplying capacity and the place of the crop in the rotation. For phosphorus
the principle of ‘equilibrium fertilization’ is ap- plied, i.e. no more is applied than taken up by the
crop. However, during the grassland period fertil- izer application exceeds crop uptake, during the
arable period it is lower. Under ley farming a larger part of the N-requirement of grassland can
be covered by slurry because on grassland P in slurry is more restrictive than N and on leys
higher quantities of P are allowed. On perma- nently arable land N in the manure is, as a rule,
restrictive for the quantity of slurry that can be applied and adding fertilizer P may be necessary.
In the ley system phosphorus requirements of the crops can almost completely be covered by animal
manure. On average, during the 2 years, only 74 kg Nha from fertilizer were required, i.e. about
one quarter of that on the current farm.
In 1993 and 1994 permanent grassland was manured on average with 47 tons of cow slurry
and 136 kg fertilizer-N per ha in total 237 kg of mineral N. Leys received 75 tons of slurry and
123 kg fertilizer-N per ha in total 289 kg of mineral N. Maize and beets were fertilized with
27 and 34 tons of slurryha, respectively 65 and 85 kg of mineral N. On both grassland and
arable land slurry was applied by injection, on grass with open slits.
Between the rows of maize Italian ryegrass was sown in June, to take up the nitrogen mineralized
during the ripening phase and after harvest of the maize. In the spring of 1995 the grass was grazed
by young stock, in 1994 it was ploughed in.
Grassland was irrigated when necessary to con- tinue grazing in dry periods or to avoid re-sowing.
Beets and maize were irrigated only when there was a risk of premature death. The field plot of
the farm — 29 of the total area with a relatively high proportion of arable land — is never irri-
gated. During dry years — as in 1994 — on average about 50 mmha total farm area was
applied, about 90 on grassland and 10 on maize land. The growing season 1993 was charac-
terized by a warm and dry spring and a wet summer and on average only 9 mm of irrigation
water was applied on grassland. The spring of 1994 was cold and wet and was followed by a very
dry summer.
The differences in yield among crops appeared in accordance with the expectations. In both years
realized net dry matter yield of grassland was close to the prognosis for an average year. Yield
of maize in 1993 was slightly below the expected
value. The very low yield of beets in 1994 was due to drought, an attack of rhizoctonia and early
harvest, as part of the beets were ensiled with maize. Although the yields of grass and maize
were on average lower than those on current farms, average farm yield is almost equal, because
of a higher proportion of fodder beets and maize in the rotation. The feeding value of the products
was, on average, slightly higher than that of the average of samples from practice.
The amount of N in slurry — after correction for ammonia volatilization — was higher than at
the current farm because of the strong reduction in the proportion of manure excreted at pasture
and to the emission-reducing measures for slurry. In both years slurry was the main source of
nutrients at ‘De Marke’ Table 7.
In 19931994 total nutrient supply to the soil was similar to the prediction 355 kg N and 37.2
kg Pha; in 19941995 it was substantially higher because more slurry and fertilizer were applied to
grassland, as a different calculation method for fertilizer requirements was used. Moreover, the
correction for lower yields due to drought was insufficient. Therefore, the store of slurry de-
creased in 19941995. The contribution of clover to the N-supply of the farm was lower than
expected as explained earlier. N and P contents of the harvestable crop gross
yield were in both years almost equal to the predictions, but considerably lower than those in
practice. The relatively much higher nitrogen pro- duction at the current farm — 398 kg Nha
versus, on average, 276 at ‘De Marke’ — reflects the combined effect of a higher proportion of
grassland and a much higher fertilizer level on grassland. On average, during the 2 years, 135 kg
N and 4.7 kg P per ha of the nutrients applied were not recovered in the harvested products.
These quantities must thus have accumulated in the soil, leached, lost in surface runoff Sharpley
and Withers, 1994, or denitrified only N. Mod- ifications in the soil store can only be identified in
the long run because of its large size: the soils at ‘De Marke’ contain on average more than 7000
kg of N and more than 3100 kg of P per ha.
5
.
5
. The feed component The proportion of nutrients from both har-
vestable crop and purchased feed ingested by the animals was in accordance with the predictions
and, therefore, higher than at the current farm. Hence, nutrients in feed are used more efficiently,
as a result of lower grazing losses — due to short grazing periods per plot, stabling at night and a
Table 7 Nutrient flows of the soilcrop component 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 199394 and 199495 kgha Characteristic
19941995 19931994
‘Average’ ‘De Marke’
prognoses 19831986
N P
N N
P P
N P
Input 164
Faeces and urine at pasture after volatilization 57
7.7 48
3.3 7.0
51 26.0
227 Slurry application after volatilization
33.5 146
32.0 137
20.2 181
25.8 52
1.8 96
15.0 Fertilizer
67 330
6.0 49
0.9 49
0.9 1.0
Deposition 49
49 0.9
– 5
– 12
– N-fixation clover
30 –
18 2.5
20 2.6
6.0 Harvest loss
21 60
3.1 Output
34.5 398
270 Harvestable crop
35.2 275
37.3 276
48.0 85
-0.1 79
32.0 351
Input-output
a
184 3.5
5.8
a
Denitrification, nitrate leaching and accumulation.
Table 8 Nutrient flows for the feed component for 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 ‘De Marke’ prognoses
19931994 19941995
Characteristic ‘Average’ 19831986
P N
N P
N P
N P
Input 48.0
276 37.3
275 398
35.2 Harvestable crop
270 34.5
32.0 41
5.9 82
15.0 Purchased feed
84 182
11.5 Output
74.0 278
Feed intake 40.1
496 336
47.1 330
43.8 8
1.2 Feed sold
− 35
− 2.3
Mutation feed stock 17
0.8 6.0
39.0 3.1
48 4.2
Input–output
a
7 84
1.4
a
Grazing, harvesting, conservation and feeding losses.
short grazing season — careful silage making, and utilization of maize straw and beet leaves,
that at the current farm are left in the field. Inputs of N and P with feed from outside the farm and
from the feed stocks were substantially higher than predicted because of a larger herd size Table
8. Moreover, more N and P was imported with feed than necessary according to the feeding stan-
dards. Fodder with ‘adapted’ nutrient contents is rather expensive and it is cheaper to limit the
input of N and P on the farm through restricted fertilizer purchases. Differences between years in
the balance of inputs and outputs are partly due to inaccuracies in determining the feed stocks.
6. The fate of the nutrient surplus
