The site is located in in the county Skåne in Southern Sweden (55o 49’ N, 13o 30’ E, altidue 75 m). Precipitation varies between 500 and 1000 mm per year. Mean temperature is around 0 °C in January and 16 °C in July. The area is relatively small (11 000 km2) but has a high population density; 1.275 million people. 900 000 of these are living near the coast in the South-West part, which also is the most intensive agricultural part. Soil types are clayey (ca. 15% clay or more). Focus in this study will be on Orup soil, a coarse-loamy, mixed, frigid, Aquic Haploboroll (Soil Taxonomy). The site is a sandy loam throughout the profile (0-100 cm) and non-calcareous. The subsoil (below 30 cm) is highly compacted which limits root penetration and thereby nutrient and water uptake from deeper soil layers. Orup soil is one of the Swedish long-term soil fertility sites run since 1956.
The climate is cold-temperate and humid. The zone is: Nemoral. Soils are sandy loams.
The number of farms in Skåne was 9337 in 2010, with 1147 larger than 100 ha; 417 were milk producers, while 6233 had no animal production. Most common crops in 2014 were ley (temporary grass; 102 300 ha), winter wheat (99 500 ha), spring barley (72 400 ha), rapeseed (45 800 ha) and sugar beets (32 900 ha).
Different cropping intensities from no fertilization to high fertilization rates are applied at the Orup site. Both treatments with and without animal manure are run. Rates of manure are in relation to yields provided by the cropping system. The site is treated according to conventional agricultural practices of the region.
|The map of Skåne showing the Orup site marked by a red cross intended to be used for this study site|
Types of crops
Two 4-year rotations are applied:
- crop rotation with livestock: barley, ley, winter wheat and sugar beets
- crop rotation without livestock: barley, oil seed rape, winter wheat and sugar beet.
Management of soil, water, nutrients and pests
Soil tillage includes yearly mouldboard ploughing, cultivation, fertilization, manuring, chemical weed and pest treatment. Crops are rain-fed and no catch crops to combat N leaching are grown.
Problems that cause yield loss or increased costs
Soil compaction is a threat to crop production in agriculture, since it enhances harmful physical, chemical and biological processes, which lead to soil degradation. Driving heavy tractors and other machines that affects the subsoil during ploughing and harvesting is a major cause of subsoil compaction, which is not possible to adjust through tillage, but has a severe long-lasting impact on plant growth. This means that the problem is widespread in Europe. However, the problems may be even worse in Scandinavia, where soils are naturally compacted by land ice and the humid climate often means that rain events coincide with harvest. Schjønning et al. (2009) identified soil compaction as the greatest threat to agricultural productivity in Denmark.
Instead of using more inputs, we can increase crop yields by enabling use of a larger soil volume. To achieve this, conditions in the subsoil (layers below the topsoil) can be improved by mechanical loosening and long-term structure stabilisation through addition of waste materials such as paper mill waste, biochar, hydrothermally carbonised straw and composted wood bark. In addition to improving aggregate formation in subsoil, organic amendments increase the water holding capacity and can help to buffer conditions of drought. One farm where we have observed severe problems with soil compaction is Orup. This site belongs to our series of long-term field experiments (Kirchmann and Eriksson, 1993). Most of the problems with this soil is due to natural compaction, caused by the land ice thousands of years ago. Plants will hardly have any roots below 30 cm depth. This situation is common in this region and would most likely be possible to improve.
The Orup site is producing 20-40% lower yields than of comparable crops in the region. The primary reason is the inability of crops to penetrate the subsoil. Data in the table below illustrate prevailing soil physical conditions:
|Soil depth (cm)||Bulk density (kg dm-3)|
External drivers and factors
Institutional and political drivers
There are a number of political aims related to agriculture in Sweden. For example:
- to crop 20 % of the arable land according to organic farming practices;
- to take measures to reduce P leaching with 590 tons P from Swedish arable land to the Baltic Sea by 2020;
- to maintain and increase the biological diversity in the landscape through subsidies for animal grazing of non-arable land, etc.
Societal and bio-physical drivers
There are strong interest groups and commercial companies marketing organic food as a being superior to conventionally grown food. New dietary recommendations by the National Food Agency aim to reduce meat consumption. The size of farms continuously increases driven by low profitability. Demand for locally produced instead of imported fodder changes the proportions of certain crops in rotations. Demand for bioenergy often means straw removal followed by lower soil organic matter contents over time. Use of new crop varieties, for example sugar beet, enables farmers to increase yields drastically.