c Calculated on the basis of estimates for N from livestock, estimates for ammonia loss and loss through denitification in livestock housing and stores, during placing and grazing. These losses depend on, inter al. the housing system (see section 5.3). Evaporation from crops, which is assumed to be the same in all scenarios (11 mill. kg), is also included, and in 1995/96 and the AEP II scenario, evaporation from fertiliser (7 mill. kg) and ammonia treatment of straw is included (4 mill. kg).

The overall nitrogen balance for the agricultural sector is based on more or less reliable estimates for added and lost nitrogen. It is important to note that the nitrogen fixation, which plays a big role, particularly in the organic scenarios, is difficult to estimate because it is difficult to separate it from the other elements in the nitrogen turnover in the soil. Furthermore, there is a relationship between loss to the atmosphere and the supply of nitrogen as atmospheric deposition. Here, we assume the same deposition in all scenarios because account has not been taken of the consequences of a change in ammonia evaporation as a result of livestock production.

The nitrogen fixation has been calculated on the basis of an empirical model in which harvested dry leguminous plant matter, the nitrogen concentration, the percentage of fixated nitrogen in the harvested solids and the percentage of fixated nitrogen in the parts of the leguminous plants that are not harvested are included as parameters (Høgh-Jensen et al 1998). The model is used for both peas and clover. The peas contribute 17-24 mill. kg N per year in the organic scenarios, while clover grass, including underseed, contributes 142-153 mill. kg (Grant 1998). Since clover contributes most of the nitrogen fixation, the model assumptions concerning clover will be discussed in greater detail.

On the basis of Høgh-Jensen et al. (1998) and Hansen & Kristensen (1998), it is assumed that the fixation amounts to 56 kg N per tonne harvested clover (clover grass 1-2 years: 50% grazed white clover, 25% cut white clover, 25% cut red clover). It is also assumed that the total clover yield from the 2-year clover fields from sowing to reploughing is 5.0 tonnes/ha with present practice and 5.5 tonnes/ha with improved practice, corresponding to the solids yield in clover grass with 1.2 kg solids per f.u.

The fixation thus depends on a wide range of factors, each of which is encumbered with great uncertainty in the organic scenarios. However, it should be noted that there is a close relationship between the fixation and the level of yield. A significant deviation from the estimate shown in table 5.11 should therefore be reflected in a corresponding change in the level of yield, which will in turn affect the need for bought-in feed. If it is assumed that the proportion of clover in clover grass is changed by +/-15% units (from 25%-55%), that corresponds to changing the nitrogen fixation by DKK +/-56 mill. or +/- 21 kg per ha.

It will be seen from table 5.11 that there are considerable differences in the nitrogen turnover and balance between the different scenarios. The nitrogen balance is highest in Danish agriculture 1995/96 (418 mill. kg), somewhat lower in AEP II (305 mill. kg), and lowest in the organic scenarios (146-245 mill. kg). Kyllingsbæk (1995) made some similar calculations for Danish agriculture in the period 1950-94. He found that, at the beginning of the 1950s, there was a total supply of 294 mill. kg. and that the nitrogen balance was 213 mill. kg. This corresponds to the turnover in the 15-25% scenario with the present level of yield.

According to Kyllingsbæk, the nitrogen balance at the beginning of the 1990s was 490 mill. kg. The nitrogen balance for Danish agriculture has thus decreased considerably in the last few years (see table 5.11), due mainly to falling consumption of fertiliser.

On the basis of the nitrogen balance and estimates for losses to the atmosphere from fertiliser and crops, it is possible to calculate the net amount of nitrogen supplied to the soil (table 5.11). The losses occur in the form of ammonia evaporation and denitification from manure and ammonia evaporation from crops, fertiliser and ammonia treatment of straw, although the last two sources do not apply in the organic scenarios. In the soil, nitrogen enters into a complex, dynamic relationship in which particularly changes in the soil’s pool of organic matter and the interaction between the accessibility of nitrogen in the soil and the crops’ growth play a major role. The loss of nitrogen from the soil can be in the form of denitrification and leaching. A detailed discussion of potential losses and their environmental consequences is given in section 6.1.

In the organic scenarios, account is taken of the nitrogen available in the form of manure, fixation and atmospheric deposition, and the levels of yields therefore correspond to the nitrogen balances for the scenarios. The levels of yield in the scenarios are also based on the assumption that plant production does not fall in the long term due to negative nutrient balances for phosphorus and potassium. The yields are thus not adjusted on the basis of differences in the supply of these nutrients because it is assumed that there must be balance in the organic scenarios. These assumptions are discussed further below.

5.7.2 Phosphorus

Danish agricultural land has been supplied with a surplus of phosphorus for most of the last 100 years, thereby increasing its content of phosphorus. The phosphorus content in the root zone is in many cases 3-5 tonnes/ha. The content of easily accessible phosphorus is generally high in all regions of the country, with a phosphorus number (Pt) below 2 in only 5-10% of Danish soils. Measurements show that only negligible amounts of phosphorus are lost to the aquatic environment – on average, around 0.35 kg/ha per year. That corresponds to just under 1 mill. kg potassium lost from agricultural land per year – a figure that can be compared with the figures in table 5.12 (Færge & Magid 1998, Grant 1998).

In the organic scenarios, the supply of phosphorus to agricultural land largely consists only of feed (table 5.12), a substantial proportion of which is feed phosphates. In the 0-import scenarios, feed phosphates make up most of the supply. The national balance shows a surplus of phosphorus in the scenarios in which feed is imported and a small deficit in the 0-import scenarios. Since 1996, the phosphorus standards have been reduced, which is expected to lead to a reduction of about 3 mill. kg in the use of phosphorus in feed. Account has been taken of this reduction in the organic scenarios (Grant 1998).

Table 5.12
Phosphorus balances for agriculture (mill. kg per year) (Grant 1998, Kyllingsbæk personal communication)

Phosphorus is not generally expected to be a yield-limiting factor within a 30-50-year time horizon because of large reserves of phosphorus in the soil. Phosphorus will have to be supplied to soils with a low phosphorus number in the form of raw phosphate or through recirculation. Raw phosphate is a limited resource, and adding it would involve a risk of undesirable substances being supplied. Today, 5.7 mill. kg of phosphorus is recirculated in the form of sludge and waste, and this potential is not taken into account in the balances for the organic scenarios in table 5.12 (see also section 5.7.5 on recirculation). Distributed over the 5-10% of the land with low phosphorus numbers, this potential corresponds to a supply of 20-40 kg P/ha per year.

5.7.3 Potassium

The content of potassium in Danish soil varies considerably with the mineralogy, weathering and leaching. For most of the last 100 years, Danish agricultural land has received a surplus of potassium, which has increased the soil’s content of easily accessible potassium. In many sandy soils, however, the content of easily accessible potassium is low, despite a plentiful supply of manure. The reason for the low content is probably leaching. 50% of soils in West Jutland thus have a potassium number (Kt) of less than 8 (Færge & Magid 1998).

The nutrient balances for potassium (table 5.13) show a small deficit to a moderate surplus in the organic scenarios. There is then some loss in the form of leaching (see below). As mentioned earlier, in the longer term, a deficit on the nutrient balances in the soil should be countered by adding potassium. The effect of leaching on the nutrient balances is dealt with at the end of this section, but first we must determine whether the assumptions for the organic scenarios warrant a supply of potassium. It is thus assumed in the scenarios that differences with respect to potassium between the empirical basis and the organic scenarios do not give cause to change the expected yields (cf. section 5.2).

At the organic dairy farms included in the empirical basis for the yields in the organic scenarios, manure corresponding to 66 kg K/ha per year is allocated to clover grass and lucerne in rotation (Kristensen & Halberg 1995), whereas the clover grass fields in the scenarios do not receive manure. In the organic scenarios it is assumed, with the focus on nitrogen, that this difference does not make it necessary to reduce the expected yields. It can rightly be discussed whether this assumption holds good when potassium is included. The potassium balance at dairy farms was 33 kg K/ha per year. Compared with the balances in the organic scenarios (tables 5.10 and 5.13), this gives a difference of 26-37 kg K/ha, which can be countered by a total supply of 60-100 mill. kg K per year nationally, with the biggest need in the 0-import scenarios. (See also Færge & Magid 1998.)

Table 5.13
Potassium balances for the agricultural sector (mill. kg/year) without a supply of potassium fertiliser in the organic scenarios (Grant 1998, Eriksen et al. 1995, Kyllingsbæk personal communication).

The effect of leaching of potassium on the potassium balance in the soil has also been investigated. In the soil, potassium reacts with the soil’s clay minerals, and in soils with some content of clay, high concentrations of potassium will therefore become fixated in the soil. In sandy and peaty soil with a low content of clay, on the other hand, surplus potassium must be expected to result in leaching. The leaching of potassium from well fertilised soils in present practice is estimated to be 5-30 kg K/ha per year in different types of soil with different clay contents (Eriksen et al. 1995), which gives a weighted national average of about 20 kg/ha per year. That corresponds to total leaching from the entire acreage of the order of 50 mill. kg K per year, and thus, in extension of the balances in table 5.13, a total deficit of 30-60 mill. kg. on the potassium balance.

Leaching can perhaps be limited

The large pool of potassium in clayey soils means that some potassium deficit can be tolerated, even on a very long-term basis, if sufficient potassium can be released from the more strongly bound fractions to make up the deficit. However, a potassium deficit cannot be tolerated in coarse, sandy soil. The leaching depends not only on the type of soil but also on fertilisation practice and crop rotation. Ongoing studies in an organic cultivation system with potassium balance on good sandy soil thus shows very limited leaching of potassium (Askegaard et al. 1999).

A supply of the order of 60-100 mill. kg would thus more than make up for the total deficit on the potassium balance, including estimated leaching of 20 kg K/ha/year, so the yields could be maintained in the long term.

5.7.4 Sulphur

Owing to decreasing atmospheric deposition, there may be reason to look at the balance of sulphur as well. From a surplus of 6 kg S/ha per year in the 1970s, there was a deficit of 16 kg S/ha per year in 1989. However, there would be less need for sulphur in the organic scenarios because shortage of sulphur depends on the relationship between nitrogen and sulphur, and there is far less nitrogen circulating in the organic scenarios. However, fertiliser with sulphur in rape and a few types of vegetables may be necessary, particularly on sandy soil (Færge & Magid 1998).

5.7.5 Recirculation of nutrients from urban societies

Nutrients are lost from the agricultural sector in the form of plant and animal products through loss to air and water. To maintain the nutrient balance, it will be necessary in the longer term to make up for this loss. Nutrients can be supplied in the form of feed, mineral and organic fertiliser and, particularly in the case of nitrogen, biological fixation. The sources of nutrients are transfer from other ecosystems, including farming, extraction from soil, water and air and recirculation from the rest of society. In the following we take a look at the potential for recirculation of nutrients from urban communities.

Today, many nutrients end up in various forms of waste, and the waste is collected and processed for many other purposes than recirculation of nutrients. The risk of supplying undesirable substances is therefore a considerable obstacle to recirculation of nutrients to agricultural land. Large amounts of potassium and sulphur end up in the aquatic environment because these nutrients, unlike phosphorus and nitrogen, are not deemed to constitute a problem for the environment.

The main sources for recirculation today are wastewater sludge, domestic waste and organic residuals from industry (table 5.14). Just under 70% of the total amount of wastewater sludge was supplied to farmland in 1996. This proportion has been falling since 1994 and is expected to continue falling for a variety of reasons, including stricter limit values for undesirable constituents. Less than 10% of compost and garden waste went to industrial agriculture in 1996 because these sources were primarily used in private gardens and public parks. More than 95% of the organic residuals from industry went back to farms as feed and fertiliser in 1996 (Eilersen et al. 1998).

Table 5.14
Quantities of organic waste (mill. kg. per year) used as fertiliser in the agricultural sector in 1996 (Eilersen et al. 1998, Danish Environmental Protection Agency 1998a, 1998b)

The total quantity of sludge and waste supplied to the agricultural sector in 1995/96 corresponds to 9.1 mill. kg N, 5.0 mill. kg P and 4.7 mill. kg K (Grant 1998). Under the current rules, wastewater sludge must not be used in organic production, and neither sludge nor waste is included in the organic scenarios. That means that there is a direct, unutilised potential for recirculation in the scenarios in the form of organic domestic waste and residuals from industry – and in the slightly longer term, human urine and fæces, which are today collected in wastewater sludge, are a possible source. However, the use of fæces in crops for human consumption should be avoided because of the risk of transmission of diseases. Separately collected human urine is of particular interest in organic farming as a high quality fertiliser for crops needing easily accessible nutrients, such as vegetables. Table 5.15 shows the potential sources for recirculation in the organic scenarios. Garden waste etc. is not included because, today, this is mainly used in private gardens and public parks.

In the organic scenarios, the potential quantities of waste from some of the agricultural sector’s secondary industries must be assumed to fall as a consequence of falling production. From calculations of the quantity of organic waste from different types of industry (Andreasen et. al. in prep.), it is estimated that the quantity of solids would halve if the fall in production fed right through in the secondary industries. The quantity of phosphorus and nitrogen would presumably fall less because the two largest contributors, accounting for about half of the total quantity, are not affected by the restructuring (Danish Environmental Protection Agency 1998a). The quantity of nutrients from the different sources in 5.15 can be compared with the balances in tables 5.11 to 5.13.

Table 5.15
Potential sources of recirculation of organic waste in a 100% organic agricultural sector (mill. kg per year) (Eilersen et al. 1998, Andreasen et al in prep., Danish Environmental Protection Agency 1998a)

5.8 Summary and conclusion

A total restructuring for organic agriculture in Denmark could generally be implemented, but at a lower level of production than today. However, the expected consequences for the agricultural sector would depend on the form of 100% organic production.

The time horizon of the scenarios is 30 years

To provide a basis for assessing the consequences of a total restructuring for organic production in Denmark, various scenarios have been set up for 100% organic agriculture with a time horizon of 30 years. This number of years has been chosen because of the extensive structural changes that would be needed. It is assumed that there would be an even distribution of manure and that the clover grass acreage would be used for grazing, which would in turn require a more even distribution of livestock production over the entire agricultural acreage. Extensive "deregionalisation" of Danish livestock production is thus assumed in connection with the restructuring for organic production. In the financial analyses (chapter 7), it is similarly assumed that the return of livestock production to Eastern Denmark would take place as the surplus livestock housing capacity wore out. It is therefore assumed that there would be no costs in the form of "scrapping" of housing capacity in connection with the deregionalisation.

According to the current rules on organic farming, such farms must buy in conventional feed in quantities corresponding to 15-25% of the animals' daily feed intake (measured as the energy in the feed), and a certain percentage of conventional manure. In a 100% organic Denmark, there would be no conventional farms from which to purchase manure or feed, although it would be possible to import both organic and conventional feed. Three levels of feed import to Denmark are used:

- and there are three levels of feed import

	no import, complete self-sufficiency in feed
	15% imported for ruminants and 25%, for non-ruminants
	unlimited import of feed and maintenance of the present level of livestock production (1996).

On the basis of the current rules, 15-25% of imports are assumed to be conventional feed and the remainder organic feed.

Vegetable for domestic consumption are produced in all the scenarios, but no vegetables are exported, in contrast to today's situation, in which the net export of grain accounts for almost one fifth of the harvest and there are significant exports of seeds, sugar and potato starch.

In all scenarios, the production of milk and eggs corresponds to present production. The production of milk is limited by milk quotas and the production of beef is of the same size as today. The production of pork varies in proportion to the produced and imported quantities of feed (poultry is included in the scenarios as pork).

Besides the domestic consumption of animal products, exports of milk products and beef are at the same level as today, whereas exports of pork are unchanged with unlimited import and fall by nearly 40% with 15-25% import of feed and by more than 90% with 0-import.

A further three scenarios have been set up with a level of yield in cereals and clover grass that is 10-15% higher than the present level. In the scenarios with a better level of yield, pork exports fall by only 10% with 15-25% import of feed and by over 70% in the 0-import scenario.

Same production, but other production systems

Except for the export of plant products and pork and the production of special crops, production can be maintained unchanged in all the organic scenarios. However, this level of production is based on greatly changed production systems. Organic farming is based on diversified crop rotations with a considerable proportion of nitrogen-fixating and perennial crops. There is therefore 30-50% clover grass on all soils in the organic scenarios. Manure is a limited resource and is assumed to be evenly distributed from the standpoint of crop rotation. It must therefore be assumed that the livestock would be more evenly distributed in a 100% organic scenario than they are today. There are more dairy cows in the scenarios than in present-day agriculture, with a lower average yield, and bull calves from milk production would be fattened as bullocks. The cows would be kept in a parlour and yard system and put out to grass in the summertime. The sows would be out on grass and the bacon pigs would have access to an outdoor area and straw bedding.

The nitrogen cycle is reduced

The nitrogen cycle is significantly reduced in the organic scenarios, to a level corresponding to Danish agriculture in the 1950s, because nitrogen would not be imported in the form of artificial fertiliser. It would instead be obtained by symbiotic nitrogen fixation in clover grass fields and through importation of feed, but grain production would be limited by nitrogen in all the scenarios.

Necessary to import potassium

The scenarios indicate a number of constraints on a total switch to organic farming. The main constraint is probably that, in all scenarios, it is estimated that it will be necessary to import 60-100 mill. kg. of potassium per year (most in the 0-import scenarios) in order to maintain yields in clover grass at the level of the empirical basis for the scenarios. On coarse sandy soil, potassium leaches easily and has to be added.

- even though there is a potential for recirculation

There is an unexploited potential for recirculation of nutrients from urban communities in the organic scenarios. The quantities are relatively small compared with the need for potassium. Recirculation could, however, play a vital role, e.g. in vegetable production. Besides potassium, it would be necessary to import feed phosphates for the livestock, also in the 0-import scenario, to meet the animals’ needs with the presumably relatively high level of production. That means, on the other hand, that there would be no problems with the nutrient balance for phosphorus.

Import of feed is important to the nutrient balance

To summarise, the loss of phosphorus and potassium through sales products would have to be made up for by a supply to farmland in the form of other mineral fertiliser, recirculation or feed. Nutrient import via feed thus plays an important role in the organic scenarios. As mentioned, present-day rules permit the use of 15% conventional feed for ruminants and 25% for pigs and poultry. However, an on going discussion within the EU indicates that permission to use conventional feed will be withdrawn over a period of years. In such case, the need for imported feed will have to be met with organically cultivated feed. If feed were supplied to a 100% organic agricultural sector in Denmark, there would be a corresponding loss from the agricultural sector elsewhere in the world, which would shift the nutrient problem but not solve it. It has not been clarified how the organic exporters of feed in other countries would achieve balance with respect to nutrients, so that a bigger organic import to Denmark could be maintained in the longer term. It is therefore uncertain whether it would be possible, in the long term, to maintain the present quantity of exported pork from a 100% organic agricultural sector in Denmark.

Particular problems in fruit, vegetables and special crops

Organic production of fruit, certain special crops and individual vegetable species is particularly problematical. In conventional production, larger quantities of pesticides are used in these crops than in ordinary farm crops, and the financial value of using pesticides is high. In apples, we would expect a catastrophic decline in yield – at any rate in the varieties used today – and there could also be difficulties with durability and, thus, with the length of the season. For vegetables, the increased yield variation would be a problem in itself, due to the high establishment costs and the accompanying economic risk. Lastly, with our present level of knowledge, it is not possible to produce organic seed of satisfactory quality because of the propagation of seed-borne fungal diseases. Continued seed dressing of the first generations of cereals, followed by a need assessment of subsequent consignments of seed would be one way of considerably reducing fungicide consumption.

It is difficult to use and transfer the rules for organic production of agricultural and horticultural products to the forestry sector because the time horizon and the production period within forestry are very long, with continuous value growth throughout the production period.

- and in ornamental greenery

Problems can be expected with national monuments in old forest areas, where there is little possibility of mechanical weed control, and it can be concluded that production of organic ornamental greenery on a large scale would be difficult and would require extensive development work.

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