Free-range systems aim to support animal welfare and are common in organic pork production. However, they do represent an environmental risk due to the depositing of manure. Maximum stocking rates are prescribed assuming that nutrients released with manure will be spread uniformly in the field and may be absorbed by cover crops roots. In practice, there are several problems with these assumptions: pigs often decide to use one specific part of the paddock to defecate; sandy-soil fixes only a small amount of nutrients; and herbaceous cover crops are more active during spring and summer but less so in other seasons. One solution could be the planting of fast growing trees, such as poplar (but also willow, black locust) which absorb high amounts of nutrients and can reduce the risk of leaching. Moreover, developed trees can provide a good welfare environment for pigs: cool shade in hot weather conditions and shelter from cold winter wind.

Tips:
• The tree planting should be done in late autumn or early spring, using one year old rods (3-4 m long), planted at a depth of 1.3-1.5 m.
• Planting trees at high densities will ensure an extensive root covering and good absorption of manure nutrients in the “defecation area” chosen by pigs.
• Newly established plantations must be protected from pig damage (mainly bark biting and scratching) with tree protection guards (called shelters in the leaflet) such as metal cages or cylinders, and not letting pigs in until the second year.
• In the wettest areas (due to rolling in the mud) tree-roots damage and soil structure deterioration may reach severe levels. Soil conditions may deteriorate in wet periods and annual tillage could be necessary.
• Monitoring the trees’ condition, replacing the damaged shelters, reducing stocking rates, and shortening the rotation time for the trees can help to reduce the percentage of damaged trees.
• Short rotation (5 - 6 years) poplars planted densely can be harvested for woodchips.