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Doubled horse population explains positive trends in soil carbon in Swedish croplands

Published: 01 June 2015

In the past two decades Swedish agricultural soils gained carbon due to an increased cultivation of perennial leys. Soil organic carbon is crucial for soil fertility and its accumulation considered an important climate mitigation option. The surplus of hay is consumed by the growing horse population in Sweden, which therefore not only provides a new market for farmers but also benefits for agricultural soils and the climate.

Christopher Poeplau, Thomas Kätterer and their colleagues at the Swedish University of Agricultural Sciences have disclosed this strong link between Swedish lifestyle and soil carbon and recently published the results in the journal Biogeoscience.

Country scale soil inventory programs are initiated in many countries to monitor soil conditions over time. In Sweden, the monitoring of agricultural soils began in 1987, with more than 3000 croplands being sampled until 1997. A second inventory was conducted between 2000 and 2007 and the third inventory started in 2010 and is ongoing. The trends in soil carbon as present in those datasets were investigated for the first time.

"We were surprised to find that soil carbon increased in 18 out of 21 counties between the first and the last inventory", says Christopher Poeplau, from the Department of Ecology. "In many other European countries such as Norway, Finland, Belgium, England and Wales decreases in carbon have been reported for agricultural soil".

Together with the amount of farmyard manure applied to croplands, the proportion of ley of the total agricultural land was identified as the most important driver for soil carbon at the county level. Perennial grasses produce large amounts of belowground biomass which is transformed into soil organic matter. The application of farmyard manure did however decrease over time due to increasing import of meat and decreasing stocks size of Swedish cows and pigs, while the cultivation of ley increased by 250 000 hectares or 23 percent in the last 25 years. The cultivation of ley increased the most in counties with the highest increase in horse population. One horse with normal activity needs approximately 1 hectare of ley per year. The strongly growing horse population can thus almost entirely explain the increase in ley cultivation. This clearly illustrates that lifestyle can have strong impacts on large-scale land management change.

More information
Christopher Poeplau, PhD
Dept. of Ecology, Swedish University of Agricultural Sciences
+46 (0)18-67 22 86,

The article
Positive trends in organic carbon storage in Swedish agricultural soils due to unexpected socio-economic drivers. Biogeosciences Discuss., 12, 3991-4019, 2015. C. Poeplau, M. A. Bolinder, J. Eriksson, M. Lundblad & T. Kätterer. (doi:10.5194/bgd-12-3991-2015)