Short rotation coppice (SRC) basically consists of high-yielding varieties of shrub or small tree willows planted at high densities and harvested over a 2 or 3 year harvest cycle. The Osier or basket willow, Salix viminalis, a shrub form native to the UK, is parental stock to many of the varieties used for energy cropping. SRC is a woody, perennial crop, the rootstock or stool remaining in the ground after harvest with new shoots emerging the following spring. A plantation should remain viable for up to 30 years before re-planting becomes necessary.
Willow SRC can grow in most soils but, as with any arable crop, the better the soil the better the yield. Soils best avoided are gravel or sandy soils where the water table is more than 1m below ground surface as the crop will suffer from droughting. Peat-based soils can lead to difficulties with weed control due to the high weed seed burden; efficient weed control is absolutely essential for good SRC establishment. Heavy clay soils can be highly productive but must be well prepared, ensuring any compaction is removed; establishment may however be slow on clay soils. Moisture retentive, well-aerated clay or sandy loams provide ideal conditions.
On light land it is recommended that sludge cake be applied as a fertiliser during the land preparation phase if considered feasible by the local Water Company. This will help to condition the soil and also assist with moisture retention. No fertiliser of any type should be applied during establishment i.e. from planting to after cutback
Poplar is often mentioned as an SRC crop but the varieties currently available in the UK are not well suited as SRC for a number of reasons but can be grown as single stem trees and harvested at around 7 years i.e. short rotation forestry (SRF).
The advantages of SRC include:
- Long-term, sustainable and secure local fuel sources, grown to meet the needs of the market – not intermittent as are wind or solar power which have to be harnessed as and when they occur
- Increased diversity within the agricultural landscape provided the plantations are located appropriately
- As willow is a UK native species the benefits to local biodiversity are significant within the farmed landscape as shown by many years independent research carried out by the Game Conservancy and Wildlife Trust biodiversity
- SRC provides good cover for game birds
- It will withstand flooding but not permanent waterlogging
- Compared to conventional arable cropping SRC offers significant reductions in the use of herbicides, pesticides and fertilisers
- The humus content of the soil improves over time as does soil fauna diversity due to reduced machinery passes and the deciduous nature of the crop
- The ability to reduce water pollution where it is used for the treatment of wastewaters e.g. farmyard run-off, sewage, landfill leachate, etc
- Opportunities for farm diversification, the development of specialist contracting skills and improvement to the local economy
If you are considering growing SRC for a large or small-scale project, please contact CRL for further information, advice or comprehensive practical assistance.