174 A. Granstedt Agriculture, Ecosystems and Environment 80 2000 169–185
2.4. Transfer of plant nutrients within the system In this study annual mineralization was assumed to
correspond to the amount of organic nitrogen supplied every year through the decomposition of crop residues
and animal manure. For the country as a whole, it is difficult to determine whether there has been a net in-
crease or a net loss of organically bound nitrogen in the soil. Of course, there are also regional differences.
In the NPK-balance for the whole of Sweden we con- sidered statistics for 1995 with regard to amounts of
nutrients provided to the fodder industry in the form of slaughter waste and the spreading of wastes from com-
munity sewage treatment plants on agricultural fields Granstedt, 1992a.
2.5. Export Significant losses of organically bound phosphorus
occur when animal manure is spread under unsuit- able conditions. Losses of phosphorus and potassium
through leaching and runoff were assumed to be around 10 and 5, respectively, of the amounts supplied to
the soil in the form of animal manure. Phosphorus in manure is mostly in organic form, and only a small
part is soluble. It is assumed that about 30–40 of the nitrogen is lost through volatilization during storage
and that 10–20 is lost in the field, although this fig- ure will vary depending on the species of animals and
manure-handling techniques Lundin, 1988; Claesson and Steineck, 1991. Calculation factors used are given
in Figs. 3 and 4.
Soil nitrogen can disappear from the agro- ecosystem through denitrification, volatilization and
leaching. Soil denitrification is higher in clay soils than in sandy soils. However, the proportion of nitrogen lost
through leaching is larger in sandy soils than in clay soil Gustavsson, 1996. Recently it was discovered
that substantial losses of nitrogen can occur from wilt- ing organic material Whitehead et al., 1988. These
losses were included when calculating nitrogen losses from the soil. Losses of nitrogen were calculated as
the sum of total nitrogen supplied to the soil in crop residues and manure and mineral nitrogen supplied
in fertilizer minus the nitrogen taken up by the plants.
Losses of plant nutrients in the form of wastes cre- ated when processing food were calculated for ani-
mal products. The animal parts not used for human consumption wastes from the slaughterhouses were
considered as lost. One part is used by the fodder- processing industry; i.e. the nutrients are recirculated
in fodder. This recirculation is taken into account in the figures for Swedish counties Figs. 5 and 6 and
for Sweden as a whole Fig. 7. These wastes from slaughterhouses are, like the wastes from the human
population, a potential agricultural resource. N, P, and K contents of whole animal bodies are 2.6, 0.5 and
0.2 for pig and 2.5, 0.7 and 0.2 for cow, respec- tively Kirchmann and Witter, 1991; Fagerberg and
Salomon, 1992. Based on the relation between ani- mal production and actual consumption of the animal
products SCB, 1994, it was estimated that only 50 of the nitrogen, 57 of the phosphorus and 64 of
the potassium are present in the consumed parts of the animal body. The rest is waste.
Figures describing plant nutrient flows in the country as a whole are based on the calculated nutrient budgets
and nutrient flows in each county complemented with data on the export and import of agricultural products
in 1990 and 1995. Data used in a calculation program are given in Fig. 7.
In the figures one animal unit a.u. corresponds to one dairy cow, two young cows, three sows, 10 fatten-
ing pigs or 100 hens.
3. Results and discussion
3.1. Plant nutrient flow 3.1.1. Plant nutrient flow on the farm level
The total calculated budgets for nitrogen, phospho- rus and potassium on the farm level are shown in the
flow diagram in Figs. 2–4. Plant nutrient flows are di- vided into three groups: import, transfer and export,
and related to the different pools. The arrows refer to flows import and export from the soil, plant, animal
and foodstuff pools as well as import and export in relation to the whole agro-ecosystem.
The different management strategies can be studied individually by performing analyses of the plant nu-
trient balances and flows between defined pools within agro-ecosystems at the farm level Granstedt and West-
berg, 1993; Granstedt, 1995. Surplus of plant nutrients are lowest from farms that only produce cereals. This
A. Granstedt Agriculture, Ecosystems and Environment 80 2000 169–185 175
Fig. 3. Plant nutrient N, P and K flows, in kg ha
− 1
per year, calculated in 1997 for a specialized dairy farm in Skåne County, 38 ha and 2 a.u. ha
− 1
55 dairy cattle.
is exemplified in Fig. 2 and Table 2 with a farm in Skaraborg county with 0 a.u. ha
− 1
. On the dairy farms number two in Table 2 with 0.75 a.u. ha
− 1
was the sur- plus higher and the farms number three with inten-
sive pig production and number four, i.e., 2 a.u. ha
− 1
, showed the largest surplus of plant nutrients, calcu-
lated as the difference between imported and exported amounts Table 2.
176 A. Granstedt Agriculture, Ecosystems and Environment 80 2000 169–185
Fig. 4. Plant nutrient N, P and K flows, in kg ha
− 1
per year, calculated in 1995 for the Skilleby biodynamic farm which had not used mineral fertilizer or chemical pesticides since 1967.
A. Granstedt Agriculture, Ecosystems and Environment 80 2000 169–185 177
Fig. 5. Plant nutrient N, P and K flows, measured as kg ha
− 1
arable land per year in the community-agroecosystem in Kristianstad County.
Surpluseslosses on the swine farm in 1990 farm number three in Table 2 were assumed to be 166 kg
N, 25 kg P, and 60 kg K ha
− 1
. The assumption that ni- trogen losses were 166 kg or more was based on the
assumption that no further net immobilization of ni- trogen occurred during the humus formation process
as a consequence of there being no ley and grassland on this type of farm Jansson, 1986. Today this farm
must have access to an additional area e.g., arable land on a nearby farm on which it can spread the manure.
Even for a representative dairy farm Table 2 and Fig. 3 in the dairy district of Skåne in 1997 Sandgren
et al., 1999, which sold some of its manure in com- pliance with Swedish regulations to limit the intensity
of animal production, estimated losses of nitrogen were very high 164 kg N ha
− 1
. The farm described in Fig. 4 farm number five in
Table 2 is a biodynamic farm, which has not used fer- tilizers or chemical pesticides since 1967 Granstedt,
1992a. This farm is representative of farms in the cen- tral part of Sweden, with clay loam, fairly dry climatic
conditions for Sweden annual average precipitation 550 mm and yearly average temperature 6
◦
C, and a standard yield about the same as the average for Swe-
den. The case study shows that through recycling and the use of leguminous plants it is possible to success-
178 A. Granstedt Agriculture, Ecosystems and Environment 80 2000 169–185
Fig. 6. A. Surplus of nutrients N, P and K, in kg ha
− 1
arable land per year, calculated for 1995 as the difference between amounts im-
ported and exported. B. Total nitrogen losses in different counties of Sweden. C. The Swedish counties, grouped according to their in-
tensity of animal production. 1 a.u. equals either one dairy cow, two young cows, three sows, 10 fattening pigs or 100 hens. D. Levels of
nitrogen leaching in different parts of Sweden.
fully run a farm that is self-sufficient in terms of plant nutrients and minimize the losses of plant nutrients.
Nitrogen flows on the farm at the soil, crop, field and whole-farm levels were studied by the author over
a 7-year period between 1981 and 1987 Granstedt, 1990, 1992a. Production, calculated in plant nutrients
in bread grain and animal products from this farm, is about the same as the average for the agricultural sec-
tor, but animal production is based more on grass and clovergrass than on the average farm.
3.1.2. Plant nutrient flows for counties The calculated budgets for nitrogen, phosphorus and
potassium for a county are exemplified in the flow dia- gram in Fig. 5. Such budgets is done by the author for
each of the 23 counties in Sweden for 1990 Granstedt, 1995 and 1995 this paper. The arrows refer to flows
import and export from the soil, plant, animal and foodstuff pools as well as import and export in relation
to the whole community-agro-ecosystem.
There is great variation between counties in terms of the import of plant nutrients, plant nutrient contents of
foodstuffs, and nutrient surpluses and losses. In Fig. 5 the plant nutrient flows are specified for Kristianstad
County, where losses of nitrogen are higher than the average for Sweden. Nutrient inputs in the form pur-
chased feedstuffs 31 kg N ha
− 1
and artificial fertil- izers 107 kg N ha
− 1
supplied to the county are also higher than the average for Sweden, and levels for 1995
and 1990 are similar. Table 3 shows the relations be- tween the input and output of plant nutrients for three
counties representing a low, average, and high intensity of animal production, respectively. Surplus and losses
are normally relatively higher for the agricultural sys- tems compared with that from the community system.
However, in counties where the ratio of agricultural area to inhabitants is lower, losses from the commu-
nity system are higher.
Fig. 6A shows the calculated surplus in the NPK- balance in the agricultural system for each county.
Agricultural land covers a fairly small area in the northern counties and has little impact on inputs of
nitrogen and phosphorus to the Baltic Sea. In the south- ern parts of Sweden, agriculture dominates the land-
scape to a greater extent and the warmer climatic conditions and larger proportion of till soils, combined
with the higher surplus of nitrogen and phosphorus, have consequences for losses of nutrients to the Baltic
Sea. In Fig. 6B the estimated losses of nitrogen in 1995 are presented. Losses of nitrogen through leach-
ing are illustrated in Fig. 6D Brink, 1990. From these figures it is clear that high levels of surplus nitrogen
and high losses per hectare are associated with inten- sive animal production Fig. 6C. Losses from manure
and urine occur primarily through the volatilization of
A. Granstedt Agriculture, Ecosystems and Environment 80 2000 169–185 179
Fig. 7. Plant nutrient N, P and K flows, measured as kg ha
− 1
arable land used in 1995 in the Swedish community-agroecosystem.
Table 2 Supply, export and surplus of N, P and K, in kg ha
− 1
, in three counties of Sweden with 0.2, 0.4 and 0.8 animal unitha County
Animal Supply to the agricultural
Export from the Losses from the
Food consump- unitha
system agricultural system
agricultural tion in community
system system
Purchase of Biol.
Atmosph. Artificial
Animal Crop
feedstuffs N-fixation
deposition fertilizer
products products
Västmanland 0.2
900 7
5 821111
711 3577
6143 1945
Kopparberg
a
0.45 2233
16 5
691519 1633
1224 841315
42911 Kristianstad
0.8 33610
9 8
1071029 2644
2243 109931
1423
a
Food consumption is much greater than food production in this county.
180 A. Granstedt Agriculture, Ecosystems and Environment 80 2000 169–185
Table 3 Supply, export and surplus of N, P and K NPK in kg ha
− 1
year
− 1
, on five farms describing five farm types in Sweden: cereal farm, combined dairy and cereal farm, pig farm, dairy farm and ecological farm
Farm type a.u.ha
− 1
Supply to the farm Total supply Export from the farm
Total export
Surplus Feed, seed Biol. N-fix. Deposition Fertilizer
Crop pr. Anim. pr.
Cereal farm 201
7 15
972420 1212420
1021725 1021725 197-4
Comb. farm 0.75 15619
17 15
9150 1401120
2757 2667
531114 8706
Pig farm 2
1374368 4
15 10300
2594368 611
87177 93188
1662560 Dairy farm
2 1422471
52 22
5300 2702471
1062260 1062260 164211
Ecol. farm 0.6
220 50
10 5421
1022 1434
2456 39-3-6
nitrogenous compounds during each of the handling steps.
A similar relationship between the intensity of ani- mal production and high losses of nutrients in regions
is documented from Finland, other Nordic countries Rekolainen and Leek, 1996 and other countries of
Europe Brouwer and Hellegers, 1997. For example, owing to the intensity of crop production and the con-
centration of livestock, the surplus of nitrogen is signifi- cantly higher 120–150 kg ha
− 1
in the north of Germany than in the rest of that country Kleinhanss
et al., 1997. 3.1.3. At the country level — Sweden
The calculated budgets and nutrient flows for nitrogen, phosphorus and potassium for the whole
community-agro-ecosystem Sweden 1995 are shown in the flow diagram in Fig. 7. A comparison of the nitro-
gen surplus in the agricultural system for 1995 Granst- edt, 1995 with that in 1990 shows that it increased from
86 to 89 kg N ha
− 1
. Despite the decline in the amount of agricultural land under cultivation, the total difference
between the input and output of nitrogen increased dur- ing this time from 180 000 to 191 000 tons according
to Statistics Sweden SCB, 1998. As for phosphorus, there was a minor decline in the surplus from 1990 to
1995, from 10 to 8 kg P ha
− 1
Of the total nitrogen imported to the agro-ecosystem, 20 is exported from the agro-ecosystem in the form of
protein nitrogen in foodstuffs. The difference between import and export 80 represents the surplus which is
either immobilized in the soil or lost to the environment mainly to water and air. Although about two thirds of
the phosphorus is surplus, only a smaller part is lost to the environment. Of the potassium, 70 is surplus
and lost on its way through the agro-ecosystem. The average leaching of nutrients from arable land in Swe-
den has been estimated at 48 000 tons N per year and 621 tons P per year, on the basis of measurements of
drainage water Gustavsson, 1996. Retention by lakes and watercourses is assumed to be 50 for nitrogen
and 25 for phosphorus. Calculations based on these figures indicate that, on average, leaching should ac-
count for 30 of the total losses of nitrogen from the soil 67 kg N ha
− 1
in an assumed steady state in the humus or 20 kg ha
− 1
per year Löfgren and Olsson, 1990. In addition, it is assumed that another 5 kg ha
− 1
is lost from the rooting zone, with the water passing through the drainage system, penetrates deeper down
into the soil and reaches groundwater Brink, 1990. About 65 of the calculated total losses of nitrogen
from the soil pool are lost to the atmosphere. The prin- cipal causes of losses of soil nitrogen to the atmosphere
are denitrification and volatilization. Of the surplus 8 kg P ha
− 1
only an average of 0.25 kg P ha
− 1
is lost through leaching of organic and inorganic phospho-
rus compounds and most is bound to insoluble organic and inorganic phosphorus compounds stored in the soil.
This surplus accumulates year after year in the soil and can be assumed to be a potential source of losses to the
environment for a long time to come.
The fractions of plant nutrients in foodstuffs con- sumed within the country that end up in slaughterhouse
wastes, domestic wastes wastes from household and food industry and sewage wastes are shown in Fig. 7
the community system. Between 30 and 60 11 kg N, 3 kg P and 2 kg K ha
− 1
of the plant nutrient con- tents of the food products 26 kg N, 5 kg P and 6 kg
K ha
− 1
end up in these first two fractions. Of the total phosphorus taken up by the plants 20 kg P ha
− 1
15
A. Granstedt Agriculture, Ecosystems and Environment 80 2000 169–185 181
is found in the sewage fraction. Other studies involving calculations of nutrients from food consumption in the
sewage fraction in Sweden produced the same results Kirchman, 1998. One part of the sewage fraction was
recycled to agriculture in 1995. This year the farmers’ organization has recommended farmers not to accept
municipal waste on arable land. Only the first two men- tioned fractions can be recycled to agriculture without
risking the kind of contamination found in the sewage system today.
A comparison with other countries shows that the surplus of nitrogen 89 kg N ha
− 1
per year is the same as in Finland 89 N kg ha
− 1
per year in 1993 Granst- edt, 1999 and lower than in our neighboring countries
Denmark 129 ha
− 1
per year in 19901991 Brouwer et al., 1995 and Norway 135 kg ha
− 1
per year in 1988–1991 Bleken and Backen, 1997. In these other
countries the use of artificial fertilizer was higher than in Sweden during the years in question Finland
93 kg ha
− 1
, Denmark, 142 kg ha
− 1
and Norway 110 kg ha
− 1
and the difference between inputs and outputs of nitrogen the same as Finland or higher than in Sweden.
In Denmark imported fodder is an important input of nitrogen to the system.
3.2. Excessive surpluses and losses of plant nutrients from agriculture — reasons and proposed measures to
remedy the problems
3.2.1. The imbalance between plant and animal production
The imbalance between plant and animal production at the country level as well as regionally and locally is
one important factor contributing to the mismanage- ment of plant nutrients. This becomes clear when com-
paring a swine farm Table 3 or a specialized dairy farm with a cereal-producing farm without animals
Figs. 2 and 3. Plant nutrients are supplied as artificial fertilizer to the cereal farms, where they are converted
to foodstuffs that are delivered to the animal producers. There they accumulate and to a large extent are lost.
The losses of plant nutrients in agriculture accounted for in this investigation were shown to differ greatly be-
tween counties and regions, as well as within counties and farms. The grouping of counties based on their an-
imal production intensity shows that the losses of plant nutrients are highest where animal production intensity
is high. At the same time, the requirements for and use of fertilizers are highest in counties with few animals.
About 25 of the nitrogen losses in the Swedish agri- cultural system can be attributed directly to the animals
and their excrement manure and liquid manure with mainly emissions of nitrogen compounds NH
4
-N to the atmosphere. Losses of nitrogen compounds from
soil are also higher on the animal farms and are strongly related to animal production and its intensity.
Plant nutrient balances calculated at the country level show that substantial surpluses develop which result in
losses of nitrogen as well as phosphorus and potassium Fig. 2. Losses of potassium are not an environmen-
tal problem, but do represent a cost for the agricultural system as well as a waste of this limited resource. Some
80, 65 and 70 of the nitrogen, phosphorus and potas- sium, respectively, supplied to the agricultural system
ends up in surplus and is released to the surrounding air or water or is immobilized in the soil.
A comparison with other countries shows that the above description is applicable to farms and regions
in Finland Granstedt, 1999 and in the rest of Eu- rope where agriculture is technically more developed.
Oomen et al. 1998 show that the environmental ni- trogen problem connected with agriculture in the Eu-
ropean Union EU is related to recent segregation of animal and crop production. This specialization can
also be seen not only between farms, but also between regions, as was shown here in the case of Sweden. In
principle, manure produced by cows, pigs and poultry should be returned to the regions where their feed was
produced.
3.2.2. Plant nutrient surplus at the farm level Examples at the farm level show that fertilizers are
applied on livestock farms even through plant nutrients accumulate in excess, in the form of animal manure, on
these farms. This holds true for the animal-producing farm with 0.75 a.u. ha
− 1
Table 2 and a higher degree of within-farm plant-nutrient recycling, as well as for
farms with an animal production intensity of more than 1.0 a.u. ha
− 1
farm number three and four in Table 2 and Fig. 4.
Calculations showed that the amounts of plant nu- trients in animal manure were more than enough to
meet the requirements of the plants, even when gaseous losses associated with manure handling were subtracted.
182 A. Granstedt Agriculture, Ecosystems and Environment 80 2000 169–185
The annual use of manure led to a high release of min- eral nitrogen on these farms, much of which is lost if
the plants do not take it up. This is reflected in the bal- ance accounts presented here and confirmed in studies
of mineralization on farms practicing intensive animal husbandry Granstedt, 1990. During a transitional pe-
riod, a high animal-production intensity will lead to a rise in the immobilization of nitrogen in the form of
an increase in soil humus content, but will later lead to increased mineralization. Studies of mineralization
carried out in long-term experiments comparing the ef- fects of animal manure with those of artificial fertilizer
have shown that the most important factor is the con- tent of total nitrogen in the animal manure Granstedt,
1997. Nutrient management advice based only on the content of mineral nitrogen in animal manure has led to
increased losses of nitrogen from farms with intensive animal production in Sweden.
3.2.3. The input of plant nutrients to agriculture and their losses from the agricultural system can be
minimized Fig. 5 presents a representative example from central
Sweden of the plant nutrient flows on a farm managed according to the principles of ‘recycling eco-
logical agriculture’, which preclude the use of inor- ganic fertilizers. The yield on this farm is comparable
to the Swedish average, but total losses of nitrogen are about half as high as the average in Sweden. This type
of management requires that the level of animal pro- duction on a given farm be adjusted on the basis of the
farm’s crop production. The optimum level of intensity of animal production for a given farm can be calculated
based on its fodder production. Due to the good bal- ance between animal husbandry and plant production
0.6 a.u ha
− 1
is optimum in this part of Sweden the net outflow of plant nutrients is so low that it can be
compensated for through weathering, small inputs of fodder and nitrogen fixation by leguminous ley crops
Granstedt, 1992b. In studies done in Finland by the author similar results were obtained for Finnish condi-
tions Granstedt, 1996, 1999. Oomen et al. 1998 have described the benefits of mixed farming in the Nether-
lands, compared with traditional agriculture, illustrated by the favorable nitrogen balances of two designed
prototypes where arable, dairy and sheep farming are integrated to a high degree.
Effective recycling must be combined with the best techniques available for conservation in both the
animal-manuring system and the crop–soil system. The reported farm studies Granstedt, 1992a, 1995 show
that, on each farm or group of co-operating farms, it is essential that nutrients in manure be effectively uti-
lized in relation to the needs of the different crops in the crop rotation. To develop such environmentally sound
farms there is a need for more case studies of ecologi- cal farms with a high degree of plant nutrient recycling
which could serve as good examples for demonstration and extension services in different regions of a country
related to climatic, soil, geographical and economical conditions.
Assuming that these principles are followed it is pos- sible to roughly predict the regional breakdown of crop
and animal production in Sweden in a future, ecolog- ically based, resource-conserving agricultural system.
Animal production needs to be decreased in the south- ern regions in Sweden, while a corresponding increase
is required in central Sweden. In the areas around Kris- tianstad, Blekinge, Kalmar, and Halland, animal hus-
bandry must be halved as well as decentralized within each region in order to achieve a balance between plant
production and recycled animal manure.
By integrating crop and animal production it is possi- ble to achieve effective utilization of the plant nutrients
in manure, minimize the input of nutrients in the form of artificial fertilizers, minimize the surplus of nutrients
and, as a consequence, minimize losses of nitrogen and phosphorus for whole Sweden Fig. 8.
In a recycling-based agricultural system not every enterprise needs to produce both animal and plant prod-
ucts. For instance, forms of co-operation could be es- tablished between neighboring farms whose products
complement one another. It would also be desirable to increase the extent to which plant nutrients exported
from the agricultural system to the community are re- turned to the farms. This recycling should also include
quality tested wastes from the food industry. Special restrictions with animal and crop production must also
be accepted in the coastal regions.
If the nitrogen fixation in leys with clover in the crop rotation were also utilized the nitrogen requirements of
a farm can be totally met without having to use artifi- cial fertilizers. In this way the use of fossil fuels, which
would otherwise be needed for the industrial fixation of atmospheric nitrogen in connection with the commer-
A. Granstedt Agriculture, Ecosystems and Environment 80 2000 169–185 183
Fig. 8. Plant nutrient N, P and K flows, in kg ha
− 1
, in arable land in 1995 in the Swedish community-agroecosystem and in a scenario
for 2010 with halved losses of nitrogen resulting from increased in- tegration of crop and animal production. This increase in integration
allowed nitrogen to be more effectively recycled within the system and its input to be halved.
cial production of fertilizer would be reduced. Such a converting for the whole agriculture in Sweden should
need more grassland with clover in the crop rotation in the southern regions and an increased share of meat
from ruminants as a consequence.
4. Conclusions
