Farming and forestry combined
Agroforestry is well worth looking at as an alternative approach to farming
Published 16/12/2015 | 02:30
Did you know that a couple of chickens pecking away happily in the apple orchard is an example of a silvopastoral agroforestry system? This is a fancy word for a land use practice that combines the growing of trees with farming in a mutually beneficial way.
There are many different types and combinations of agroforestry.
For instance, silvopastoral agroforestry combines the growing of trees with livestock while silvoarable agroforestry combines trees with crops. There are other combinations too. Shelterbelts, alley cropping and wooded riparian zones can also be regarded as agroforestry.
Agroforestry was and still is very popular in many tropical countries. It is also practised in Europe but often we don't think of it as 'agroforestry'. For instance, the premium quality 'jamón ibérico' ham is produced from pigs roaming freely in oak woodlands in Spain. Another good example is livestock grazing amongst fast growing poplars in the Netherlands and Belgium.
Agroforestry can provide multiple economic and environmental benefits. Trees can provide quality timber as well as fuel while the farmer can continue to raise livestock or grow crops.
The growing of trees also leads to greater biodiversity because of the wider variety of plant species creating a more complex habitat benefiting a wide range of birds, insects and other animals.
One of the big advantages of agroforestry systems is the increased shelter leading to more favourable air and soil temperatures. Livestock appreciate this additional shelter.
Trees grown in close proximity to agricultural crops will also improve nutrient recycling and help to control surface water runoff and erosion.
Agroforestry systems also contribute to the reduction of greenhouse gas emissions from farms.
The focus should be on growing high quality hardwood timber. Tree species such as cherry, oak and sycamore show potential. Ash would also have made another excellent silvopastoral agroforestry choice but it cannot be used due to the serious threat of ash dieback. I also believe that species such as birch and alder should be considered especially now that genetically superior trees are soon to come onto the market as a result of years of Teagasc research.
Suitable sites should have a free draining, mineral soil and should not be overly exposed.
Good, practical tree planting design is of the utmost importance and should be informed by the agricultural enterprise. Will the land be used as pasture for grazing with livestock? In that case, a square planting design can be considered. However, if the land is to be used for silage production then the trees will have to be planted in widely spaced rows allowing for large agricultural machinery.
Arable crops will require a different layout and tree stocking density. It is also important to provide sufficiently large headlands to accommodate the turning of machinery. Where possible, tree lines should have a north-south orientation to maximise sunlight.
One of the most important requirements is protection from browsing livestock. Animals such as sheep, cattle, horses, goats will go to amazing lengths to enjoy a tasty young tree. Appropriate tree shelters in combination with (very) sturdy stakes are absolutely essential.
It is advisable to spray an area of one metre in diameter prior to planting. This will reduce competition for nutrients, help to prevent grass growing up within the shelter and aids tree establishment.
The trees should be pit planted preferably in early spring. Large sized whips (90-120cm) can be used. Check that the planting stock you are buying has a compact, fibrous root system with a straight stem and a single leader.
Once the trees are well established and are growing strongly after two to four years, intensive formative shaping will be required to ensure that the trees retain a single, straight stem.
The higher the crown can be 'pushed up' the tree, the longer the saleable length of quality timber. Once the final trunk height has been achieved then high pruning will need to be initiated to produce knot-free timber.
Keep in mind that trees won't remain small! As the trees grow up, not only will they provide shelter to animals and/or crops, their crowns will also gradually start shading out crops. It is therefore necessary to gradually thin out the trees. Poorer quality trees can be removed and used for fuel. Initial stocking density may be as high as 1,000 trees per hectare. This can be achieved by planting trees in rows six metres apart and approx. 1.5 metres between the trees within the row.
By the time that trees reach maturity and can be considered for felling, the tree stocking density may have reduced from 1,000 trees to 100 trees per hectare.
This could space trees about 10 metres apart. To ensure that grass growth is not overly affected, tree density may have to be reduced even further. If this is not monitored and done in time, the planted area may gradually evolve into a woodland.
When considering removing trees, remember that a felling licence will be required prior to the removal of trees.
For the agroforestry enterprise to be a success, one of the most important challenges is to start out with top quality trees. Crooked trees will never produce straight planks! It is essential that only trees with "top notch" genetic provenance and a proven track record suited to local conditions should be considered.
From the above, it is clear that agroforestry is not for the fainthearted!
If you think that agroforestry is straightforward and won't require a lot of attention then it is not for you. Not only do these super trees need a lot of TLC, livestock and/or crops need to be managed in combination with the trees too.
Having said that, I do believe that agroforestry in one form or another has an important role to play in Ireland. Not only do we need to increase the availability of top quality, Irish grown hardwood timber, we also need to increase carbon sequestration on Irish farms.
Agroforestry provides much needed shelter, improves nutrient recycling and aids in the prevention of erosion and water runoff.
We need further research to identify suitable agroforestry systems under Irish conditions.
And finally, I wish all readers a very happy and peaceful Christmas. Why not support Irish growers and our environment by buying a real, Irish grown Christmas tree?
Steven Meyen is a forestry adviser with Teagasc email: firstname.lastname@example.org