What is Agroforestry?
Agroforestry takes the best developments in farming over the past century; the yields, the logistical efficiency and the use of technology, and combines this with the environmental benefits of permaculture.
Fundamentally, the idea is to increase the amount of tree cover in a landscape for the environmental and productive benefits. Most applicable to the UK are two main methods, alley cropping and wood pasture; the former used for arable production and the latter for livestock grazing.
*All data referenced from S. Briggs, 2012, Agroforestry: a new approach to increasing farm production A Nuffield Farming Scholarships Trust
Alley cropping is the use of trees in arable farming. Rows of fruit or nut producing trees are planted 30 metres apart. The alley between is then planted with a cereal crop, in the case of Claude Jollet below, barley.
This has numerous environmental benefits which also increase farm productivity. The tree trunks act as wind breaks, reducing soil loss during winter months. The roots percolate water into the ground much quicker than bare soil. This prevents nitrate and sediment leaching into rivers and retains the fertile top soil, which is then replenished by leaf fall every autumn.
Crops utilise resources (water, nitrogen, sunlight) April – June, much earlier in the season than trees. This means overall far less nitrate loss. On non-organic farms, this has resulted in 50% less end-use nitrogen loss. Any nitrogen that isn't utilised by crops, is captured by tree roots, which stops it leaching into rivers and turns this into plant matter instead.
What about the shading? For crops other than maize, during the first 7 years of a plantation there is no decrease in yield. The years following this, the drop in yield is compensated by the fruit or nut crop. Agroforestry systems can be more productive than monoculture farming.
Land Equivalent Ratio: 1 hectare of agroforestry produces the same levels as:
0.6 hectares – Forestry : 0.8 hectares – Crop : 100 hectares = 140 hectares*
Claude Jollet, Agroforestry system, France. Combining walnuts with barley.
Wood pasture systems are areas of grazed woodland. Dairy cattle, or animals reared for meat, can be grazed amongst woodland, or groves planted for fruit, nuts or timber. In Portugal, they are often planted with cork oak.
The UK has a history of commons grazing, with wood pasture systems most widespread. The New Forest is most noted for pannage, feeding pigs on acorns, whilst the Epping Forest has a similar history.
Likewise with alley cropping, trees percolate water into the ground water at higher rates than open ground, decreasing the risk of flash flooding. The roots hold the soil in place, helping to reduce soil and nutrient loss. There is no decrease in stocking density for sheep. The shelter the trees provide have been widely shown to benefit livestock during harsh winters and especially during a late cold snap when young lambs are particularly vulnerable. Certain species, such as goat willow, can offer leaf fodder for animals.
The landscape created by such systems of management is ecologically rich and beautiful. It must be stated that both aesthetic and environmental reasons have worth, not purely the utility of such practices.