AGRICULTURAL NUTRIENT MANAGEMENT IN
DENMARK
With special reference to
intensive dairy farming
 Part 2.
N turnover on Danish mixed dairy farms
Ib Sillebak Kristensen, Niels Halberg, Anders Højlund Nielsen, Randi Dalgaard and Nich
Hutchings.
Paper presented at workshop
“Nutrient management on farm scale: how to attain European and national policy
objectives in regions with intensive dairy farming?”.
23-25 June 2003
Quimper, France
Contact: Ib Sillebak Kristensen
Danish Institute of Agricultural Sciences
Department of Agroecological
Research Group of Farming Systems
Post-box 50
DK-8830 Tjele
DENMARK
Tel. +45 89 99 12 05 fax +45 89 99 12 00
E-mail: IbS.Kristensen@agrsci.dk
Group www: http://www.agrsci.dk/jbs/bepro/index_uk.shtml
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N turnover on Danish mixed dairy farms
Ib Sillebak Kristensen, Niels Halberg, Anders Højlund Nielsen, Randi Dalgaard and Nich
Hutchings
Contact Ib Sillebak Kristensen
Danish Institute of Agricultural Sciences
Department of Agroecological
Research Group of Farming Systems
Post-box 50
DK-8830 Tjele
DENMARK
Tel. +45 89 99 12 05 fax +45 89 99 12 00
E-mail: IbS.Kristensen@agrsci.dk
Group www: http://www.agrsci.dk/jbs/bepro/index_uk.shtml
Summary
Nitrogen balances from three sets of pilot farms from 1989 to 2001 are presented, and a set of
representative farms based on Danish farm accounts from 1999. The data represent typical
management and the range between farms is well documented. The results from all independent
analyses show the same tendencies. The conventional dairy farms have reduced their farm gate N
surplus with around 30% during the 90s. Since 1994 the surplus has been 172-195 kg N ha-1 with a
stocking rate of about 1.5-1.7 LSU ha-1 (1 LSU = 0.85 Holstein dairy cow). In the same period N
surplus on organic dairy farms was between 108-124 kg N ha-1 with a stocking rate of 1.1-1.3 LSU
ha-1. On the conventional farms the N-surplus was significant increasing by stocking rate, with the
ratio of 82 kg N LSU-1. The difference between farm N-balance between conventional and organic
dairy production systems was 61-77 kg N ha-1 corrected for stocking rate. An average field level
balance was estimated using simple models of ammonia losses and denitrification to subtract aerial
emission from the farm gate balance. It is discussed how assumptions regarding soil-N changes can
give estimates of N leaching.
Background
Dairy production is characterised by major internal flows between field and herd, both with fodder
and recycling of animal manure. Grazing grass/clover sward is important on many farms. This
paper gives a description of the internal and external N flow and N loss on Danish dairy farms from
1990 to 2003. After entering into the EU in 1972, a specialization from mixed dairy and pig farms
has been going on towards bigger and more specialized dairy farms. Already in the 70s regulations
were introduced limiting maximum stocking rate of animals per area, and in 1999 only 5% of the
specialized dairy farms had more than 2.3 LSU ha-1. During the last 10-15 years detailed, public
regulations have been introduced and continuously tightened. In the early 1990s mandatory slurry
storage capacity was extended to a minimum of 6-9 months, and later restrictions for imported
mineral fertilizer have been introduced. For a more detailed description of these regulations, see the
description of the “Danish case”.
Since 1950 pilot farms studies have been part of applied agricultural research in Denmark. The
Danish Institute of Agricultural Sciences monitors 30-40 mixed dairy farms per year and prepares
technical-economic reports on livestock and field production, animal welfare and environmental
impact. Farms with pig production, organic dairy, organic egg, organic pig and organic arable
production have been included, and the environmental aspects, especially concerning N flows
between field and herd have become primary focus areas. On the pilot farms the flow of feed and
nutrient from field to herd has been measured and, within farm, N balances on fields and group of
animals have been measured and published, see table 7. From 1996 the central advisory
organisation has been involved in the data recording and reporting.
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The private pilot farmers were selected to be progressive and interested in cooperation with experts.
The farms have been larger than average, partly because “future” farms were chosen to ensure that
the data could be used for the development of the total dairy sector in Denmark. Advisors, farmers,
and other stakeholders have regarded the results as representing typical and relevant farms. Lately,
the demand for comprehensive descriptions of resource use and environmental impacts from major
farm types in question (dairy, pig and arable) has generated a need for statistically representative
farm models based on an average management level. Technical economic data based on Danish
farm accounts are available from a group of farms representing the major agricultural sectors in
Denmark with the actual production and management level. This publication describes the Danish
method of nutrient accounting using data from dairy pilot farms and representative technical
economic data for the total dairy sector in Denmark.
Objective
The objectives of this paper is
 to characterise Danish dairy farms in terms of production, size and crop-livestock
interactions,
 to compare N surplus from different dairy systems especially organic vs. conventional
production,
 to present data on nutrient cycles and farm N surplus for Danish dairy farms in comparison
with other Danish farm types,
 to demonstrate the use of pilot farms in combination with models of typical farms based on
representative technical-economic accounts as a method for the quantification of nutrient
losses and the potential for improvements.
We intend to present analyses of N flows and surpluses from four independent data sets, three based
on different groups of pilot farms and one based on a large, representative sample of farm accounts.
Moreover, on the basis on these data, it is demonstrated how relatively simple assumptions allow
modelling of farm N flows and breakdown into herd and crop sub-systems. From this it is possible
to estimate emissions and losses that allow for comparisons of different systems and to project the
developments of typical dairy systems in the near future.
Methods
Farm balances were calculated following the principles described in Halberg et al. (1995) and
further developed by Sveinsson et al. (1998) and Kristensen (2002). Pilot farms were monitored
during the years 1987-2002 by longitudinal survey techniques as described at
http://www.agrsci.dk/jbs/bepro/concept%20pdf%20format.pdf. Pilot farm results were used to
compare with model farms and to demonstrate the variation around average N surplus.
All Danish farms are obliged to keep detailed records of purchases and sales for tax
purposes and the yearly accounts are made with professional help. A representative set of these
accounts, 2239, are reported by the advisors to the Danish Research Institute of Food Economics
(DRIFE) and constitute the basic empirical input to the representative farm types presented here.
Besides the economical data, information on the land use, livestock numbers and amounts produced
are included in the data set by the advisors. The modelled representative farm types were based on
farm accounts from 1999, sampled as to represent the total Danish agricultural sector for the main
livestock and crop production. The data will be described in detail on the homepage
www.lcafood.dk and www.howproductsimpact.net/LCA-food. The same overall method was used
in year 1995-1996 (Halberg et al, 1999). Table 1 shows the number of accounts used for the models
and which farm parameters were found directly from the accounts.
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In the Danish dairy sector, biological fixation is an important N input, especially on organic
farms. On pilot farms, fixation in grass/clover was calculated by the method presented by
Kristensen et al. (1995). For the representative farms, the fixation and mineral fertilizer for
grass/clover was assumed to be the same level as on the pilot farms. Details of the level of fixation
in grass/clover and information regarding fodder, N demand, crop yield estimates and fertilizer use
are shown in the Appendix.
Coherent N balances at farm level were achieved in relation to import of fodder (cereal and
concentrates) and mineral fertilizer, including export of milk, meat and cash crops and surplus
manure. Summarizing and up scaling the key in- and outputs across representative farm types
showed good agreement with the national statistics of land use, number of livestock, the average
yield per crop, input of fodder concentrate and fertilizer per crop. The fertilizer was adjusted 11% in
the farm models to account for the national level consumption.
The sample represents 4% of the conventional farms in Denmark and 18% of the number
organic farms. 75% of the dairy cows are on sandy soil, mostly in Western Jutland. The dairy farm
types cover 23% of the agricultural land and include 75% of all dairy cows. The average herd size is
61 cows per conventional farm and 81 cows per organic farm. The average stocking rate is 1.46
LSU ha-1 on conventional farms and 1.3 on organic farms. 85% of the farm area is in crop rotation
with 24% grass/clover on conventional farms and twice this figure on organic farms. The rest of the
rotation area is mainly grown with cereals partly for grain and partly for whole crop silage
harvested 2-3 weeks before full ripe. Maize for silage has become important, mainly on
conventional farms. The cereal grain yield is 5.1 t ha-1 on the conventional farms and 20% lower on
organic farms. Roughage yields are assumed to be on the average level of pilot farms, and the
average yield of crops on rotation area is 5,700 SFU ha-1 = 6,300 kg DM ha-1 on conventional farms
and 14% lower on organic farms.
The milk yield level in 1999 was 7,373 kg milk cow-1 year-1 on conventional farms and 7%
lower on organic farms. 54% of the total SFU-uptake is from homegrown roughage on the
conventional farms and 64% on the organic farms. An average level of protein was 18.5% of SFU =
20% of DM.
Summation within the following tables may not always give the exact sum, due to rounding errors.
Results
Dairy farm N balances
Table 1 shows the farm N balances. On organic farms, fixation contributed 50% of the total N input.
On conventional farms, imported fertilizer and fodder each account for 40% of the total N input. On
conventional farms, the weighted average N surplus is 172 kg N ha-1, which is 64 kg higher than the
average for organic farms. The data from pilot farms show that the farm gate N surplus is very
dependent on stocking rate (Fig. 1). In Fig 1, the average (1997-2001) farm gate N surplus for each
farm is shown for comparison with the modelled farm types. The modelled farm types closely fit
the average for the pilot farms. On the conventional farms, a larger variation in stocking rate makes
it possible to calculate the relationship between N surplus (Y) and stocking rate (LSU ha-1):
Y = 53 + 82 * LSU ha-1,
R2 = 0.61
On the organic farms the stocking rate variation is much smaller, as by regulation the farms must
not exceed 1.4 LSU ha-1. The equation for organic farms is:
Y = 56 + 44 * LSU ha-1,
R2 = 0.16
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At the same stocking rate, the N surplus of organic farms was around 50 kg lower than for
conventional farms.
N-surplus, Kg N/ha
300
250
200
150
100
50
0
0,00
0,50
1,00
1,50
2,00
2,50
3,00
"LSU"/ha
Conv, sand
Conv, clay
Org. sand
Org, clay
Conv. pilotf.
Org. . pilotf.
Figure 1. Farm N surplus on specialized Danish dairy farm types in year 1999, see Table 1,
and on pilot farms (1 point is average per farm for the years 1997-2001) shown with
increasing stocking rate, corrected for import/export of animal manure (100 kg N = 1 LSU).
Lines are average pilot farms.
A sensitivity analysis was conducted to check the effect of assumptions on the results, see Table 2.
Farm balances were calculated with 25% higher fixation, 10% lower N efficiency in feeding (=
higher N content in imported feed), 10% higher protein content in roughage, and 10% higher net
yield in roughage, respectively, and all other parameters unchanged. The analysis changed the farm
gate N balance 3-17 kg N ha-1, with the largest changes on organic farms as a result of the higher
percentage of homegrown roughage. Increasing the fixation by 25% decreases the difference
between conventional and organic dairy production by 12 kg N ha-1 (the difference between 5 and
17 kg increased N surplus on average conventional farms and organic farms). The other sensitivities
only change the difference between conventional and organic types by 2-5 kg N ha-1.
Dairy N-balances at the herd and field level.
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In Table 3-4 the coherent N-balance of herd and field is shown as the within farm N-flow, summing
directly up to the overall farm gate N-balance. In Table 3, the herd balance is shown both from the
representative data and as the average result from dairy pilot farms on sandy soils. On the pilot
farms, the N-input in roughage (especially grazing) is higher then for the representative farm types.
This is due to a higher N-uptake in grazed grass/clover. Output in products is equal from the pilot
and representative farms and the N-balance in manure production from the herd are greater on the
pilot farm. This makes the animal manure input to the fields and the field N-surplus higher on the
pilot farms. The between-farm variation on the pilot farms is presented in Table 3 and 4. This gives
an indication of the scope for improvements in N-use efficiency. The CV (Coefficients of Variance)
for herd balance on conventional pilot farms was 8% (10 divided by 122) whereas was 14% for the
organic farms. This is mainly a consequence of lower grazing N-uptake on the conventional farms,
which means that N-uptake is more easily adjusted with imported feed. On organic farms, Danishproduced conventional rape cake is the dominating concentrate fodder import, which gives a high
herd N-surplus, especially during the grazing season. The herd N-efficiency varies between 18-24
% N-efficiency, with no systematic difference between conventional and organic.
For the field balance, the variation between conventional pilot farms is 23% CV, whereas
for organic was 15%. There is a big variation between the lowest and highest N-surpluses and
possibilities for lowering the N-surplus are numerous. The organic dairy farms has 56-60% field Nefficiency and the conventional dairy farms has 42-46% field N-efficiency. On farms with a low
efficiency there should be good possibilities to improve the N-utilization.
Distributing dairy N-surpluses between losses
The ammonia and denitrification losses shown in Tables 3-5 were calculated using the methods of
Illerup et al (2002) and Vinther (2002) respectively.
The field N-balance was calculated by deducting the ammonia loss in animal housing and
manure storage from the farm surplus, table 5. More organic farms than conventional farms have
deep litter animal housing systems, so losses of ammonia during storage will be higher. However,
extra conventional straw is imported and ammonia losses during spreading are smaller than for
slurry-based systems, so the total losses are calculated to be a similar proportion of the manure N
flow. The field N-balance on conventional farms was 156 kg N ha-1. The ammonia losses after
spreading and denitrification were assumed to be 15% and 9% respectively of the manure N
applied. The remaining surplus (e.g. 108 kg N on average conventional) includes the soil-N changes
and leaching.
Partitioning this remaining field surplus between changes in soil-N and leaching is difficult.
There is no reason to believe that there should be any systematic difference between conventional
and organic dairy farms in the change in the soil-N pool. The conventional has a lower proportion
of grass/clover in the crop rotation but a higher stocking rate compared to the organic, probably
representing about the same organic matter input on the two farm types. Therefore, the difference in
field balance of around 50 kg (56 vs. 108) on organic compared to conventional farms probably
corresponds to an identical difference in leaching.
A preliminary attempt at partitioning the remaining field N-surplus between changes in soilN and leaching is shown in Table 5. The method used will be described at the Exeter conference
autumn 2003. There is a tendency for higher leaching losses on sandy farms, which is expected.
However, although there is an increase in the farm surplus with increasing stocking rate, this is
accounted for by higher gaseous losses (ammonia volatilisation and denitrification). This means that
the estimated leaching on conventional farms does not increase significantly with stocking rate
(Table 5).
Estimating leaching as the difference between farm gate surplus and gaseous emissions
means that any errors in the surplus or gaseous emissions will be rolled up into that estimate. An
alternative method(s) is needed but so far, no simulation model can reliably predict leaching for
dairy farms with grass/clover pasture. However, leaching measurements made in Denmark under
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organic cattle trials with continuous grazing for 8 years of grass/clover and with nutrient removal
from the grazed area only via milk and meat, resulted in a maximum leaching of 5-60 kg N leaching
ha-1, measured in the winter in year 7-8. Values of <10 kg N ha-1 leaching were recorded from
unfertilised grass/clover while from pure grass fertilised with 300 kg N ha-1 the leaching was around
65 kg N ha-1 year-1 in year 7 and 8 (Eriksen and Vinther (2002), Eriksen (2003) and Søegaard et al
(2002). Results from the other organic crop rotation trials also show an average leaching of around
40 kg N ha-1, although higher losses have been measured after green mulching at sandy soils
(http://www.agrsci.dk/pvj/plant/croprot/resultuk.shtml).
If the lack of increase in leaching with increasing stocking rate is a real effect, then one
explanation could be as follows. Increasing stock numbers will increase the demand for roughage
fodder. In Denmark, the application to all crops is limited by law, so farmers cannot generate
additional fodder by applying more N fertiliser, only by increasing the area the proportion of the
farm area devoted to grassland (see table 1), which at moderate fertiliser levels, tends to leach less
N than other crops (Søegaard et al, 2002). The lower leaching from organic farms compared to
conventional farms could be explained by the crop rotation on organic farms, which contained
around 50 % area with grassland, and that grass/clover are more N-efficient than its conventional Nfertilized grass/clover. The later explanation is the consequence of the substitution rate between Nfertilizer and fixation, where 2 kg extra N-fertilizer lower the fixation by 1 kg N ha-1 (Kristensen et
al, 2002). Also better utilization of nitrogen in urine area of grass/clover gives higher N-utilization
(Hutchings and Kristensen, 1995).
Emissions of greenhouse gases from representative farm types.
Table 5 shows N-balance and greenhouse gas emissions for the main representative farms in
Denmark and the Danish average. Relative to dairy farms, pig farms have a larger external N
exchange of both fodder and meat production, a higher ammonia loss from animal housing and
manure storage. Emission of CO2 only include emissions from combustion of fossil fuel on farm.
The organic dairy farms have a lower CO2 emission than the conventional equivalent due to less use
of fossil fuel per hectar, because of a greater area with grassland. Emissions of greenhouse gases
(calculated in CO2 equivalents) are higher for farms with livestock than for those without.
Emissions are higher for dairy farms than for pig farms, because of the contribution of enteric
fermentation to methane emissions.
The emission per kg of milk has been calculated using LCA methodology and show only
small differences between farms with different stocking rate (www.lcafood.dk).
Changes in dairy N balances over time
Changes in N-balances over time, based on additional datasets from the pilot farms, are compared
in Table 7. It appears that the farm N surplus on conventional farms has been reduced by 30% over
the last 10 years, whereas the surplus on organic farms has fallen only slightly (Not identical farms
in the three pilot farm samples). Note that conventional and organic farms cannot be compared
directly here as they have different stocking rates. In the bottom line the LSMEANS estimates for
difference at same stocking rate is shown. The results from pilot farm investigations fits very well
with the modelled data from representative farms.
The progressive implementation of the VMPII is expected to result in a further
decrease in N losses (Hutchings et al, 2003). A model forecast with these changes is shown in Table
8. If 50% extra fixation is assumed (minus 2 kg N-fertilizer = plus around 1 kg extra N in fixation,
Kristensen et al, 2003) and around 5% lower yield the conventional farms are forecast to reduce
their N surplus by 33 -40 kg N ha-1, mainly because of a 50% reduction in fertilizer import which is
not fully compensated for by extra fixation and fodder import. An additional scenario of
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conventional dairy farms with 25 kg N fertilizer ha-1 of grass/clover has an N surplus of only 130 kg
N ha-1.
On organic farms they have changed to 100% organic feed since 1999. A typical
change to this situation is an exchange of rape cakes with more concentrate with a higher proportion
of cereals, meaning 60% lower N import in fodder N, Table 8. This makes a reduction of 19 kg N
surplus on the organic farms (108 minus 89). When the organic farmers are only allowed to use
their own feed, they are encouraged to buy extra land to be able to produce this feed. In the left
column this future scenario is calculated be putting extra cereal into the crop rotation. This makes a
yield reduction of about 10% in cereals, but still the farm gate N surplus is down to 60 kg N ha-1.
Comparison of environmental impact between farm types
While the arable farm types on both sandy and loamy soil have N surplus below 100
kg N ha , the pig types show a farm N balance around 150 kg N ha-1 with 1.5 - 1.6 LSU ha-1.
Thus, the field surplus for soil N change and leaching was 157 kg N ha-1 on dairy compared with 81
and 119 on average arable and pig farms. However, it cannot be assumed that soil N changes are the
same in these systems. To illustrate the possible combined effect of field N surplus and soil N
change in these different systems a preliminary model was used to predict the net mineralization:
Because of the high input of organic material and grass/clover on the dairy farms the model
predicted a low net mineralization of +1 to -7 kg N ha-1 compared with 19-38 kg N depletion on
arable and pig farms. Thus, due to low input of organic matter the modelled leaching from pig farm
models was of the same magnitude as dairy farms and arable farms on sandy soils may have only
slightly lower N-leaching than livestock farms. The overall average change in soil-N across soil
types and farm models was a loss of 23 kg N ha-1. This may be too high since Heidmann et al
(2001) found no overall change during a ten year period in 300 samples representing Danish
farming systems. However, changing the mineralization parameters in the model will probably not
change the relative soil-N change between pig and dairy. Nitrate leaching measurements and model
calculated in Denmark in 1996-2000 was measured in about 40 fields to 94 and 98 kg N leaching
ha-1 in catchments (Grant et al, 2000). The measurements were extrapolated to whole Denmark with
standard precipitation. The overall modelled N-leaching in Denmark in 1999 was around 75 kg N
ha-1 (Grant et al, 2000). Thus, if no overall soil-N changes in DK is assumed then the model based
on the representative sample gives exactly the same level of N-leaching (100 – 23 = 77 kg N per
ha).
-1
Conclusion.
A large group of representative dairy farmers in 1999 has been used to calculate farm
N surplus. Both investigations on pilot farms and the representative farms have shown the same
overall result. The conventional dairy farms have an increase in farm surplus of 82 kg N LSU-1 in
the interval of 0.8 –2.5 LSU ha-1 (1 LSU = 0.85 heavy dairy cow). Organic dairy farms have
consistently 61 – 77 kg lower N surplus than conventional farms since 1994. The strength in this
conclusion is that the data represents a realistic management situation. On cattle farms this is very
important because of large internal flows that are difficult to quantify, so that it is difficult to
accurately calculate field level balances directly from field input and outputs. It is very important
that each farm is analysed as an entity, where interaction between management, agricultural
production (herd and crops) and losses of N can be analysed at the farm level.
Farm N surplus is an expression of the long-term potential losses. If changes in soil-N are assumed
to be similar on both organic and conventional dairy farms, then nitrate leaching is about 50 kg N
ha-1 less on organic farms than on conventional dairy farms at the same stocking rate.
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The data from organic mixed dairy farms production has been used as an extreme case, to
demonstrate the capacity of unfertilised grass/clover to reduce farm N-surplus. Using this
knowledge in models of conventional farms shows there is also scope to reduce the farm N-surplus
in these systems. It is likely that the lower farm N surpluses for organic systems are due to the
inclusion of unfertilised grass/clover, combined with the use of cereals on about 50% of the land
area to utilise the carry-over of N from the grass/clover pasture.
Losses of nitrate, ammonia and nitrous oxide from livestock farming appear to be higher
than for arable farming. Increases of nitrate leaching with increasing livestock density in Denmark
are lower than the increase in farm N surplus. This is because a disproportionate amount of the
increase in farm N surplus is due to increased gaseous losses.
Our analysis shows that the combination of pilot farms and representative farms is a
relevant tool for predicting agronomic, economic and environmental effects on farm and regional
scale of different farm types and interventions. As demonstrated in fig. 1 the pilot farms show
differences between farms with comparable soil types and stocking rate (variation around average
line). To the extent that these differences can be explained by differences in management including
the farmers choice of crop rotation and feeding systems the farm variation may be used to generate
ideas and benchmarks for improvement of the farms with high surplus. The farm models generated
from the representative sample allows for the generalisation of average farms within the selected
groups, for calculation of other emissions in a standard Life Cycle Assessment framework and for
scaling up to national level emissions and N surplus. Thus, in combination these methods could be
powerful tools in the search for improvements and for the evaluation of proposed regulations and
interventions in dairy farm nutrient management.
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Table 1. Characteristics of specialised representative Danish dairy farms in year 1999.
Sandy (< 5% clay)
Typologi3
No. farms in population
No farms in dataset
Agricultural area
Herd
No cows
No LSU3)
Area
Farm area
Permanent grass
Set aside
Cereal for harvest
Maize & whole crop
Grass/clover in rotation
Stocking rate
Field production
Cereal
Total 100 SFU/ha cultivated
Avr. protein in total fodder
Animal production
Milk/cow/year
Fodder requirement
SFU/LSU, in total
-in roughage
-in grain
Avr. protein in total fodder
Conventional
LSU < 1.4
1.4-2.3
Loamy (5-15 % clay)
Organic
Conventional
LSU < 1.4
1.4-2,3
Average
Organic
Conv
Org
Unit
No farms I total
No farms I total
Measured(M)
Calculated(C)
Judged(J)
C
M
1912
83
4004
182
695
125
432
23
849
32
115
24
7794
350
810
149
1000 ha in DK
M
156
261
69
43
43
10
530
79
Cows/farm
LSU/farm
M
M
48
81
67
109
84
131
56
87
55
84
62
100
61.3
99
81.0
127
Ha/farm
Ha/farm
Ha/farm
Ha/farm (%)1)
Ha/farm (%)1)
Ha/farm (%)1)
LSU/ha farm area
LSU/ha cultivated2)
M
M
M
M
M
M
M
M
81
7
6
33(49)
13(20)
13(20)
0.99
1.21
65
6
4
12(23)
22(41)
16(30)
1.67
2.05
99
8
5
14(16)
29(34)
39(47)
1.32
1.48
100
8
6
45(56)
15(19)
12(15)
0.88
1.06
50
3
2
16(38)
13(31)
12(27)
1.66
1.91
88
9
5
21(29)
20(28)
28(39)
1.13
1.31
64
6
4
20(35)
18(32)
14(24)
1.46
1.76
93
8
5
15(18)
28(34)
38(46)
1.30
1.45
100 SFU/ha
100 SFU/ha
% protein of SFU
M
C
J
52
57
11.3
49
57
14.4
41
49
16.3
57
58
10.2
55
58
13.3
44
51
13.6
51
57
13.1
41
49
16.0
Kg Milk/cow/year
M
7431
7429
6866
7227
7288
6811
7373
6860
SFU/LSU
SFU/LSU
SFU/LSU
% protein of SFU
J
J
M
J
4744
2796
1184
18.1
4729
2720
311
18.7
4448
2874
269
18.6
4774
2621
1313
18.0
4739
2243
607
19.1
4396
2714
501
17.9
4734
2566
563
18.6
4442
2856
295
18.5
2)
1)
% of area in rotation.
On organic farms set aside is inclusive in cultivated area, on conventional farms the set aside is assumed not cultivated
3)
Livestock units per ha. 1 LSU = 0.85 Holstein dairy cow.
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Table 2. N-turnover on farm level of specialised representative Danish dairy farms in year 1999. Kg N ha-1 year-1
Sandy (< 5% clay)
Conventional.
Farm type:
Input
LSU ha
LU < 1.4
-1
Mineral fertilizer
Fixation
Manure import
Supplement feed
Precipitation
Total input
Output
Milk
Meat
Cash crops
Manure export
Total output
N-balance
Do by 25% higher N-fixation
Do by 10% lover N-efficiency
Do by 10% higher N in roughage.
Do by 10% higher yield fr. field
Average
Loamy (5-15 % clay)
Organic
LU 1.4-2.3
Conventional.
LU < 1.4
Organic
1)
Conv
Org
LU 1.4-2.3
1.0
101
20
8
48
16
194
1.7
86
28
0
110
16
241
1.3
0
72
11
50
16
150
0.9
104
20
5
47
16
193
1.7
73
22
0
125
16
237
1.1
0
59
10
41
16
127
1.5
1.3
89
23
3
97
16
230
0
70
11
49
16
147
-24
-7
-13
0
-44
149
-42
-10
-4
0
-56
185
-31
-6
-2
0
-39
111
-22
-8
-20
0
-50
142
-44
-10
-7
0
-61
176
-26
-6
-7
0
-39
88
-36
-9
-9
-3
-57
172
-31
-6
-3
0
-39
108
+4
+6
+17
+3
+5
+14
+5
+17
+4
+13
+12
+3
+12
+15
+9
+15
-8
-13
-13
-5
-11
-11
-10
-13
-9
-11
-13
-8
-10
-10
-10
-12
1) Inclusive farms with more than 2,3 LSU ha-1
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Table 3. Herd N-balance on specialised representative Danish farms in year 1999 and pilot farms from 1997-2001. Kg N LSU-1 year-1.
Farm type
Dairy on sandy (< 5% clay)
Conventional,
repr..
LSU<1.4 1.4-2.3 )
Av. LSU ha-1
Input Conserved roughage
Grazing
Concentrates
Imported cereals
Home-grown cereals
Imported animals
Total input
Output
Milk
Meat
Total output
1.0
49
28
47
0
14
1
138
1.7
49
23
52
13
4
1
142
-24
-8
-31
Herd N-balance
Standard deviation on N-bal.
Anim. manure during grazing
Amm.loss, stable & storage
Animal manure from storage
N-efficiency, herd, %
Standard deviation on N-eff
1)
2)
3)
4)
Dairy on loamy(5-15% clay)
Dairy, repr.
Pig, repr. Arable, repr DK, repr.
Organic, repr.
pilot
1.6
50
37
52
Organic
Conventional, repr.
Repr. Pilot3) DE < 1,4
1,4-2,3
Conv
Org.
-4)
155
1.3 1.1
55 65
37 58
22 21
16 16
3
4)
1 133 160
0.9
51
26
51
0
13
1
138
1.7
74
21
60
14
8
0
145
1.1
35
36
21
14
4
1
127
1.5
46
22
54
11
7
1
142
1.3
54
37
22
15
3
1
132
0
0
84
40
27
8
161
15
11
73
0
51
9
160
23
14
60
21
19
5
152
-25
-6
-31
-27
-6
-33
-24
-4
-28
-25
-9
-34
-27
-6
-33
-23
-5
-28
-25
-7
-31
-24
-4
-28
0
-61
-61
-7
-47
-54
-10
-32
-42
107
111
122
10
112
99
110
104
100
107
110
-18
-9
-81
23%
-15
-10
-87
22%
105 128
104
18
-24
-17
-81) –142).
-7.
-73
-80
21%
21% 20%
25%
1.4%-units
1.8%-units
-14
-8.
-89
22%
-23
-61) –142)
-69
22%
-15
-10
-87
22%
-24
-8
-72
21%
0
-19
-79
38%
-8
-16
-82
33%
-9
-14
-76
28%
16
-26
-6
-32
Same losses as conventional dairy systems (23 % deep litter, 77% slurry and 10 % solid and liquid manure)
50 % deep litter, 40 % slurry and 10 % solid and liquid manure.
Pilot farms, average of 1997-2001.
Included in meat output.
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Table 4. Field N-balance on specialised representative Danish farms in year 1999 and pilot farms from 1997-2001. Kg N ha-1 year-1.
Farm type
Dairy on sandy (< 5% clay)
Conventional,
repr.
LSU<1.4 1.4-2.3
Av. LSU7)ha-1
Input Anim manure from storage
Animal manure during graz.
Mineral fertilizer
Fixation
Precipitation
Total input
Output
Conserved roughage
Grazed
Home-grown cereals
Cash crops
Total output
Field N-balance
Standard deviation, field N-bal.
Amm. loss spreading
Amm. loss during grazing
Amm. loss crops
Denitrification
Soil-N changes
Nitrate leaching estimated by diff.6)
N-efficiency, field, %
Organic
Repr.
1.4
2)
1958) 107 116
32
92
0
72
37
16
16
1)
343 227 -2352)
-49 -82
-28 -39
-13
-7
-13
-4
-103 -132
140 168
-73
-49
-4
-15
-2
-127
-157
186 1001)to1082)
42
Standard deviation, field N-eff.
Dairy
Pig
Arable
DK
Organic
Pilot5
1.1 1.7
88 145
18 26
101 86
20 28
16 16
243 300
-15 -22
-1
-2
-4
-4
-18 -27
-18
2
-120 -113
43% 44%
Dairy on loamy(5-15% clay)
1.7
Conventional, repr.
LSU< 1.4 1.4-2.3
Pilot5)
1.3
1) -
-81
-61
8)
160
0
76
17
253
-69
-61
-10
-140
113
16
-141) to -102)
-2
-2
-23 to –22.
-73) to –124)
-65 to –84 .
46% 56 to 58%
5%-units
55%
Org.
1.0
75
15
104
20
16
230
1.7
1.2
149 881)-982)
23
26
73
0
22
59
16
16
1)
283 189 - 1992)
1.5
127
22
89
23
16
277
1.4
105
31
0
70
16
223
1.3
100
0
83
4
16
203
0.4
32
2
114
5
16
170
1.0
72
9
94
13
16
204
-41
-23
-11
-20
- 96
134
-69
-58
-34
-41
-14
-4
-7
-7
-124
-110
159 791) to 892)
-67
-33
-10
-9
-119
158
-71
-48
-4
-3
-125
97
0
0
-43
-39
-83
120
-3
-2
-11
-73
-89
81
-51
-13
-18
-42
-94
110
-121) to –92)
-2
-2
-27 to –26
-53) to –124)
-42 to –62
58 to 60%
-20
-2
-4
-25
-4
-112
43%
-14
-2
-2
-23
-6
-62
56%
-16
0
-5
-16
-33
-116
41%
-8
0
-5
-13
-26
-82
53%
-12
-1
-4
-16
-23
-100
46%
-13
-1
-4
-26
-16
-107
42%
-22
-2
-4
-37
11
-84
44%
5%-units
1)
Same losses as conventional dairy systems (23 % deep litter, 77% slurry and 10 % solid and liquid manure)
2)
50 % deep litter, 40 % slurry and 10 % solid and liquid manure.
3)
Same soil-N changes as conventional dairy systems
4)
25 % lower crop residues in grass/clover and 25 % higher C-input from deep litter
5)
Data from pilot farms 1997-2001.
6)
Leaching = field N-balance – amm. loss – denitrification – soil-N changes. For example organic dairy on sand: 100 –14 –2 -2 –23 +7 = 65 kg N ha-1.
7)
Inclusive correction for manure import, 100 kg N-import = 1 LSU.
8)
Inclusive manure deposited directly on grazed fields
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Conv
- 13 -
Table 5. Estimated environmental losses on specialised representative Danish farms in year 1999.
Sandy (< 5% clay)
Conventional dairy
Farm type: LSU < 1.4
1.4-2.3
Loamy (5-15 % clay)
Organic
dairy
Conventional dairy
LSU<1.4
1.4-2.3
Organic
dairy
Average, dairy
Conv
Arable
Pig
DK
Org
Kg N ha-1 year-1
N-balance on farm
Amm. loss stable & storage
149
185
111
142
176
88
172
108
84
150
123
-9
-17
-11
-8
-17
-9
-15
-11
-3
-31
-13
138
167
99
133
158
77
156
96
81
122
110
Amm. loss animal manure & min. fert
-16
-24
-16
-13
-24
-13
-22
-15
-8
-16
-13
Amm. loss, crops
-4
-4
-2
-4
-4
-2
-4
-2
-5
-5
-4
Denitrification
-18
-27
-23
-26
-37
-27
-25
-23
-13
-16
-16
-102
-111
-58
-91
-95
-39
-108
-56
N-balance on field
N-leaching &  soil-N est. by diff.1)
Different units
Emissions2)
Methane, kg CH4 ha-1
127
216
156
113
212
131
188
153
13
44
68
N2O, kg N2O ha-1
12
15
11
11
13
9
14
11
7
8
9
Ammonia, kg NH3 ha-1
35
53
36
31
54
30
51
46
18
52
48
CO2, kg CO2 ha-1
397
453
341
427
484
347
444
341
439
381
396
7.3
10.6
7.7
6.6
10.0
6.4
9.5
7.5
4.2
2.9
Global Warming Potential,
ton CO2 equivalent ha-1
5.1
1) Leaching = field balance – amm. loss – denitrification. For example organic dairy on sand: 99 –16-2 –23 =58 kg N ha-1. Leaching estimated by difference include changes in soilN, which is assumed to be in balance within typology.
2) Se provisional data on www.howproductsimpact.net/LCA-food.
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Table 6. N-turnover and estimated N-loss on main representative Danish farms in year 1999. Kg N ha-1 year-1.
Sandy (< 5% clay)
Farm type:
Conv dairy
Org. dairy
Arable
Pig
ha-1:
1.5
16
90
24
3
1
93
16
228
-36
-10
-8
-2
-54
1.3
3
0
72
11
1
50
16
150
-31
-6
-3
0
-39
0.2
11
106
7
25
2
10
16
164
-2
-7
-60
0
-69
1.5
15
75
4
5
13
189
16
303
0
-93
-31
-29
-154
1.5
4
83
19
2
1
116
16
236
-38
-9
-15
-7
-70
0.2
18
120
5
9
2
19
16
170
-1
-12
-81
0
-94
172
-14
160
110
-11
99
96
-2
94
149
-30
119
167
-15
152
77
-4
73
-29
-18
-13
-25
-29
-24
-23
-8
-12
-110
-58
-72
-5
-7
-115
-65
LSU
% of DK area:
Input
Mineral fertilizer
Fixation
Manure import
Animal import
Supplement feed
Precipitation
Total input
Milk
Output
Meat
Cash crops
Manure export
Total output
Balance on farm gate
Amm. loss stable & storage
Field balance
Amm. loss animal manure & crop
Denitrification
N-leaching &  soil-N est. by diff.1)
Change in soil-N2)
Leaching estimated by difference3)
1)
2)
Loamy (5-15 % clay)
Conv.
dairy
Arable
Denmark
Pig
Average
Conv. dairy
Pig
1.6
1.0
1.5
0.2
1.6
8
97
2
2
13
207
16
337
0
-101
-52
-32
-185
153
100
94
12
10
4
79
16
216
-9
-33
-42
-8
-93
20
89
23
4
1
97
16
230
-36
-10
-9
-3
-57
172
28
114
5
15
2
15
16
168
-1
-10
-73
0
-84
84
22
83
4
5
13
195
16
315
0
-96
-39
-31
-164
150
-3
81
-13
-31
119
-21
-32
121
123
-13
110
-12
-22
-17
-15
157
-26
-32
-15
-22
-16
-25
-13
-16
-87
-93
-45
-76
-77
-108
-56
-83
-38
-34
1
-19
-32
-23
-4
-26
-33
-110
-121
-94
-64
-108
-100
-112
-82
-116
Leaching and soil-N changes = field balance – amm. loss – denitrification. For example organic dairy on sand: 99 –18 –23 = 58 kg N ha-1.
Preliminary results. Data will be presented at the 12 th N workshop, Exeter by Pedersen, Bjørn Molt and Nielsen, Anders Højlund.
3) Leaching and soil-N changes = field balance – amm. loss – denitrification + soil-N change. For example organic dairy on sand: 99 –18 –23 +7 = 65 kg N ha-1.
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Arable
- 15 -
Table 7. Farm gate N-turnover on specialised representative Danish dairy farms. Kg N ha-1 year-1.
Conventional
Year 1989-903)
1994-974)
1997-2001
No farms
16
5
28
LSU ha-1
1.76
1.70
1.67
Input
Fertilizer
161
100
87
Fixation
29
45
38¹
Manure import
0
0
7
Supplement feed
77
129
94²
Precipitation
16
16
16
Total input
283
290
242
Output
Milk
-39
-44
-47
Meat
-18
-10
Cash crops
0²
-22
0²
Manure export
0²
-21
0²
Total output
-47
-101
-54
Balance
240
173
195
Standard deviation
52
50
54
Difference to conv
Difference on same stocking rate
1)
2)
Organic
19995) 1989-903)
1994-974)
1997-2001
350
14
10
16
1.46
1.24
1.26
1.08
89
0
0
0
23
87
89
75¹
4
9
14
22
97
39²
47
29
16
16
16
16
230
151
166
142
-36
-28
-28
-32
-10
-6
-6
-9
0²
-4
0²
-3
0²
0
0²
-57
-32
-38
-32
172
124
112
118
19
35
19
-116
-61
-77
-85
-61
-50
Calculated after Kristensen et al 2003
Crops for sale and manure is deducted import
3)
Halberg et al, 1995
4)
Halberg (1999).
5)
Table 5
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19995)
149
1.3
0
70
12
49
16
147
-30
-6
-3
0
-39
108
-64
-45
Table 8. Farm gate N-turnover on specialised representative Danish dairy farms in 2003 after full implementation of VMP-II. Kg N ha-1 year-1.
Input
Output
Year
No farms
LSU ha-1
Fertilizer
Fixation
Manure etc., import
Supplement feed
Precipitation
Total input
Milk
Meat
Cash crops
Manure export
Total output
Balance
Difference from conv. 20032)
Amm. loss stable & storage
Field balance
Amm. loss animal manure and crops
1)
1999
350
1.46
89
23
4
97
16
230
-36
-10
-9
-3
-57
172
-15
157
-26
Conventional
20032)
20033)
Gra/cl,100N Gras/clov,25 N
1.46
1.46
44
25
30
39
2
2
103
105
16
16
195
187
-36
-36
-10
-10
-8
-8
-3
-3
-57
-57
138
130
-8
-15
-15
123
115
-25
-25
1)
1999
149
1.30
0
70
12
49
16
147
-30
-6
-3
0
-39
108
-31
-11
96
-17
Organic
20032)
20032)
18% conc4) 18%-conc4)
1.30
1.00
0
0
70
54
11
11
30
10
16
16
127
91
-29
-22
-6
-5
-3
-3
0
0
-38
-31
89
61
-49
-77
-9
-6
80
55
-17
-13
Denitrification
-25
-22
-21
-23
-24
-17
Leaching estimated by difference5)
-108
-81
-75
-56
-45
-31
1)
Average dairy farms from table 5 & 6
2)
Model calculated in year 2003 after implementing rules in 2003, se Anon (2002).
3)
Grass/clover fertilized with 25 kg N/ha in mineral fertilizer
4)
5)
Supplement feed changed from rape cake (30 % of crude protein of DM) in 1999 to protein poor supplement feed, called A 5 (18 % of crude protein of DM)
Leaching = field balance – amm. loss – denitrification. For example organic dairy on sand: 96 –17 –23 = 56 kg N ha-1. Leaching estimated by difference include
changes in soil-N, which is assumed to be in balance within typology
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Litterature
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Sveinsson, T, Halberg, N., and Kristensen, I. S. Keulen, H. v., Lantinga, E. A., and Laar, H. H. v. 1998: Problems
associated with nutrient accounting and budgets in mixed farming systems., 135-140. APMinderhoudhoevereeks. Mixed Farming Systems in Europe. 28-5-1998.
Søegaard, K., Eriksen, J., and Kristensen, I. S. 2002: Grassland cultivation in Denmark., 1-11. Wageningen, The
Netherlands, Plant Research International. Workshop: Grassland re-sowing and grass-arable crop rotation. 1819. April 2002.
Vinther, F. P. 2001: Kvælstoftab ved denitrification. Kvælstofbalancer in dansk landbrug - Mark- og staldbalancer , 14.
Østergaard, V. and Neimann-Sørensen, A. 1989: Grundlag for valg af avlsmål og tilhørende produktionssystem i
mælkeproduktionen. Statens Husdyrbrugsforsøg, Beretning 660, 1-157
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Appendix 1.
To the paper “N turnover on Danish mixed dairy farms”
In the Danish dairy sector grass/clover contribute significant to the N-input. On pilot farms clover
content is evaluated visually and the fixation is calculated directly from visual clover content, se
table 1.
Table 1.
Total input of atmospherically derived nitrogen (totally fixed – kg N ha-1) at varying
content of clover and different cropping year, Kristensen et al. (1995)
Visual clover content (soil cover)
(dry matter clover content)
1st and 2nd year sward
3rd and older sward
10-29
(13-16)
78
47
30-49
(17-29)
156
84
Above 49
Above 30
248
128
Fixation in pure legume crops with measured yield is calculated after Høgh-Jensen et al. (2003).
Mixed crops of peas and cereals are calculated with a combination of the two methods (Kristensen
et al, 2003).
In order to calculate the fodder N import from economic figures the yield of roughage must be
known. The average roughage yield from 10 years of 15-30 pilot farm studies per year has been
chosen. The yield is presented as Scandinavian Feed Units (SFU), where 1 SFU is equal to the
feeding value of 1 kg barley grain, see table 2. Permanent grass is set to 2,000 SFU/ha (= 2,500 kg
DM/ha).
The yield has been described in detail by Halberg & Kristensen (1997). The herd feed requirement
is calculated in relation to milk and meat production measured. From milk production the yearly
demand for fodder (Y) is calculated from Østergaard & Neimann-Sørensen (1989):
Y = 1000 * (-400+((4002 – 4 * 16.7 * (1860 - X)))) / (2*16,7)
Y = SFU demand per dairy cow per year
X = Kg milk production per dairy cow per year
The total demand for N feed is calculated so that a total of 24% N efficiency is achieved by
combining the home-grown feed with import of cereal and concentrate feed. The 24% N efficiency
is equal to the average level of around 20 pilot farms in 1997-2001.
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Table A2. Net yields and crude protein content for field production on conventional and organic
farms selected for modelling technical turnover on representative farms in 1999
System:
SFU
ha-1
Crops
Grass/clover silage
Do grazed
Whole crop1)
Maize
Fodderbeets
Grain
1)
Conventional
Kg
GJ dig. % crude
-1
DM ha
energy protein
of DM
ha-1
6500
8020
6500
6820
5000
6760
9200
10000
10900
10900
measured
103
96
81
141
112
16.3
23.0
10.4
8.7
7.4
10.1
Organic
SFU Kg
GJ dig. % crude
-1
-1
ha DM ha
energy protein
of DM
ha-1
5500
5500
3700
5500
6820
5730
5430
7000
measured
87
81
62
87
16.3
23.0
10.4
8.7
10.1
Exclusive grass harvested during the autumn.
To calculate the fertilizers’ import a fertilization of 136 kg N/ha in grass/clover was chosen (= N
level on 20 pilot farms in 1999). Permanent grass was set to 80 kg N/ha. All other crops have been
given the maximum allowed level of mineral fertilizer including around 50% fertilization value of
the nitrogen in animal manure. In order to achieve the national level of fertilizer use, 10% extra N
fertilizer were given to all crops.
In Table A3 the N-standards of the most important grassland crops are shown in year 2002. After the
establishing year the N-standards are not influenced by the age of the grassland. The N-standards are the
maximum amounts of N from mineral fertilizer plus animal manure. N in cattle manure is expected to have a
utilization of 60%, and therefore only 60% of total-N in cattle manure are included in the calculations. In
pastures N-excretion from grazing animals has to be included in the N-account. Therefore, the maximum
amount of N-application is lower than that shown in Table A3. By way of example, in pastures with more
than 50 % clover it will not be possible to apply any N, because the N-standard corresponds approximately to
N-excretion.
As mentioned earlier, one of the advantages of short-lasting grassland is the residual effect on the following
crop. In the N-standards the residual effect of grass/clover is estimated at approximately 60 kg N ha-1 for the
first year, when compared to the residual effects after a grain crop (Table A3).
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Table A3. Standards for maximum N-application at a certain annual net yield (yield-standard) are shown for
some crops on two soil types in 2002. In total there are 99 N-standards for different agricultural crops on
three different soil types and for sandy soil there are standards for both irrigated and unirrigated. (Søegaard
et al, 2002)
Sandy soil – unirrigated
Clay soil
N-standard Yield-standard
N-standard Yield-standard
kg N ha-1
t DM ha-1
kg N ha-1
t DM ha-1
Grass crop
27-1401)
0-4
27-1401)
0-4
285
204
55
6.5
6.0
5.0
303
213
70
7.5
6.5
6.5
Pure grass
53
1.0
53
1.0
Grass/clover
33
1.0
33
1.0
119
56
4.12)
4.12)
121
58
Permanent pure grass
Established short lasting:
Pure grass
Grass/clover, < 50 % clover
Grass/clover, > 50 % clover
Establishing year after harvest
of cover grain-crop:
Spring barley
Cereal as previous crop
Grass/clover as pervious crop
1)
: Depending of yield level
2)
: Grain yield
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5.92)
5.92)
Anon (2001)
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