By Chris Stoate, Head of Research, Allerton Project
Identifying and understanding multiple benefits from single management practices has been at the heart of our research activity throughout the life of the Allerton Project.
There are few better examples of such multiple benefits than agro-forestry on marginal land. A number of research projects across the country have explored its potential, but there has been no widespread adoption, in part because government land use policy has focused on single objectives associated with arable, pasture and forestry, and because of apparent limited application on productive land.
Agroforestry systems are more widely accepted and adopted in many other parts of the world and I have been fortunate to conduct research into such systems in Portugal and West Africa, as well as following UK agroforestry research with interest.
Portuguese Montado is the classic agroforestry system with tree densities usually of 30-60/ha and multiple uses including cork and charcoal production, and shooting and wildlife conservation, as well as livestock and arable production.
Agroforestry at Loddington
We now have an opportunity to investigate the merits of agroforestry at Loddington. A moderately productive pasture field that has been used for rearing lambs for many years has been planted with trees at a range of densities.
While maintaining lamb production from most of the pasture through our collaboration with Launde Farm Foods, the trees bring potential additional benefits. The tree species selected, and the inclusion of shrubs in some places, are specifically intended to improve the area for pheasant shooting.
The trees and shrubs also provide a new wildlife habitat. Through the influence of trees on the soil, we might expect increased carbon sequestration, enhanced soil biology and potential for flood peak attenuation through improved infiltration of water during storms.
The trees have been planted without support from an agri-environment scheme but with help from the Woodland Trust who are also supporting our research. Two plots are planted with trees at a density of 100/ha to represent a relatively high agroforestry density, and these will be compared with other plots at higher tree densities.
Some are planted at 400/ha to represent the lowest permissible density for open woodland planting with government funding, and others are planted at 1,600/ha, the maximum density that can normally be funded for woodland creation.
Trees will be thinned in due course as part of the normal management of such a plantation, but differences in tree density will be maintained. We anticipate very different results across this range of tree densities in terms of the trade-offs and synergies between our various economic and environmental objectives.
Looking ahead
The next few years provide us with an opportunity to learn much about the management of the plots to meet our multiple objectives, and we will also be gathering data to help inform this process. Our initial priority is to gather baseline data on grass yield and lamb production, tree canopy area, bird numbers, and soil biology, organic matter, compaction and infiltration.
These data will ultimately enable us to make environmental and economic assessments of tree planting on pasture under a range of scenarios, and recommendations for future policy and practice elsewhere.
As the trees develop, we will explore the interactions between a range of objectives such as livestock production, carbon sequestration and flood risk management in relation to different tree planting densities.
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