Agroforestry Systems

, Volume 92, Issue 4, pp 987–999 | Cite as

Nitrogen distribution as affected by stocking density in a combined production system of energy crops and free-range pigs

  • Uffe Jørgensen
  • Janni Thuesen
  • Jørgen Eriksen
  • Klaus Horsted
  • John E. Hermansen
  • Kristian Kristensen
  • Anne Grete Kongsted


Free-range pig production is typically associated with high risks of nitrogen (N) leaching due to the pigs excretory behaviour creating nitrogen ‘hotspots’ and rooting behaviour destroying the grass sward. This challenge is reinforced at high animal densities causing high nitrogen deposition. A combined production of pigs and perennial energy crops was hypothesized to benefit the environment because crops like miscanthus (Miscanthus), willow (Salix) and poplar (Populus) may persist despite pig rooting, take up nutrients and thereby minimise N-losses. Thus, the aim was to assess the risk of nitrate leaching by investigating the distribution of soil mineral N as influenced by stocking density in a system with zones of perennial energy crops and grass. For each of two seasons 36 growing pigs with an initial mean live weight of 55 kg (spring) and 48 kg (autumn), respectively, were separated into 6 paddocks of two stocking densities (117 and 367 m2 pig−1), respectively. Soil mineral N was measured in 0–25 and 25–75 cm depth at three occasions. N balances showed that N inputs exceeded N outputs by 626 and 185 kg N ha−1 for high and low stocking density. The pigs caused an uneven distribution of mineral N across the paddocks with highest contents in zones with willow & poplar. Stocking density had a significant effect on soil mineral N. Immediately after the second batch of pigs, average mineral N in the 0–75 cm soil layer was on average 227 and 83 kg N ha−1 at high and low stocking density, respectively. During winter period with no pigs, soil mineral N content in the 0–75 cm soil layer was reduced by almost 100 kg N ha−1 in paddocks with high stocking density against only 4 kg in paddocks with low stocking density. It is concluded that risk of elevated nitrate leaching compared to other cropping systems was low at the low stocking density, which therefore represents a promising pathway for a combined production of energy crops and free-range pigs.


Free-range pigs Stocking density Energy crops Nitrogen balance Nitrate leaching Excretory behaviour 



The authors wish to thank the research technicians Jens Bonderup Kjeldsen and Orla Nielsen for their very appreciated assistance in carrying out the data collection. We would also like to thank the employees at Foulumgård for taking good care of the experimental animals.


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Copyright information

© Springer Science+Business Media B.V., part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Agroecology, Faculty of Science and TechnologyAarhus UniversityTjeleDenmark
  2. 2.ConTerra ApS, Agro Business ParkTjeleDenmark
  3. 3.Danish Centre for Food and Agriculture (DCA)TjeleDenmark

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