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Sessions & Workshops
Systems resilience for weather extremes
Weather extremes are tending to become the norm. Vegetable production is a tough job at the best of times so it is becoming more important to plan for extremes by modifying production systems to be more resilient. (Organised by OGA)
Roger Hitchings (ORC): Chair
Climate change will be bringing more frequent extreme weather events. This session outlined how organic and agro-ecological systems can be used to buffer against varied and unpredictable weather.
Sam Eglington started by outlining the concepts of nutrients cycling within an ecosystem whilst energy can only move linearly, losing up to 90% at each trophic level through metabolism. There is therefore far more energy available in the lowest plant trophic level created by photosynthesis from sunlight. So bare ground means wasted energy and increased soil erosion.
Sam then described some of the measures he uses on his land to maximise productivity such as a diverse mix of cover crops and green manures to capture more energy into the soil and suppress weeds. Intercrops such as barley and peas or beetroot and carrots can be done effectively so the crop is also more competitive. One challenge however, is to manage an appropriate rotation suited to your soil type.
Wakelyns is a 22 hectare agroforestry site in Suffolk farmed by Martin Wolfe. Martin used Wakelyns as an example to present the ways diversity in an eco-agroforestry system can lead to better stability and productivity. The tree rows are able to shelter the crop from wind reducing evaporative stress and regulating temperature extremes in-between the tree alleys, making it cooler in summer and warmer in winter. There are also examples of reduced spread of disease as potato crops are protected from blight spreading between alleys. The apple yields this year were also much higher in quantity with far less disease than a nearby orchard. The Hazel and Willow tree rows are coppiced on a short rotation to reduce light competition with the crop then the wood is used as fuel on-farm and as material for local businesses.
Ian Tolhurst is a no-livestock veg producer, running veg box scheme from Hardwick Gardens in Berkshire. He talked about the challenges he has faced from increasingly frequent extreme weather events, including flooding, droughts and pest outbreaks. There are also concerns about the long term degradation of our soils with loss of nutrients that will require a fundamental change in our agricultural and food system. There is no one simple answer to this, but investing in more options and increasing diversity will be the best way to adapt to changing conditions. GM crops will only narrow the genetic diversity that we have available even further.
- Agricultural systems should be based more around natural ecosystems, cycling nutrients and making the most of energy that plants capture from the sun.
- 3D diversity within and among crops increases stability and productivity.
- Farms should aim for closed nutrient systems using a diverse mix of perennial cropping systems to increase ground cover.
- Agro-ecological systems do not fit into the current economic systems so a supportive market should be developed which will involve higher vegetable prices and increased labour.
- The Woodland Trust has potential funding for setting up agroforestry on farms.
Speaker presentations and abstracts
Sam Eglington (Garden Farm Produce): Energy flow in ecosystems: improving yields and profitability (970KB)
Nutrients, carbon and water are all cyclical and understanding of ecosystems in organic production has rightly focused on these cycles. However the energy that makes these cycles possible is not cyclical but linear and substantial amounts (up to 90%) are lost as heat through metabolism as it passes through each level of the ecosystem. This presentation looks at how to increase the amount of energy captured by the agro-ecosystem through the use of green manures and intercropping to improve yields and profitability through improving the functioning of the agro-ecosystem itself.
Integrating trees into a horticultural system using an eco-agroforestry approach can buffer vegetable production from extremes in an unpredictable climate. Trees modify microclimatic conditions including temperature, water vapour content and wind speed, which can have beneficial effects on crop growth. Reducing wind speeds in the protected area can reduce evaporative stress, evapotranspiration, soil erosion and improve crop water use efficiency.
Planting trees into horticultural land obviously reduces the area available for vegetables. However, improvements in microclimate, nutrient cycling and soil carbon can improve yields to help offset the diminished cropping area. To obtain such gains requires appropriate management of the tree element to avoid negative effects of competition for light, water and nutrients. In addition the trees need to be productive in their own right, for example, by including fruit and nut trees and bushes, specimen trees or other high value wood products, timber trees and/or short rotation coppice.
Eco-agroforestry can also increase system resilience by diversifying the system – diversification can reduce pest and disease impacts as well as produce a wider range of outputs (e.g. top fruit, soft fruit, timber or bioenergy as well as vegetables). Furthermore, by providing a range of habitats, agroforestry can support higher levels of biodiversity, which again increases system resilience when bad weather impacts on important species such as honey or bumblebees. The potential for eco-agroforestry including horticulture will be discussed in the context of the various agroforestry systems at Wakelyns in Suffolk.
Iain Tolhurst (Tolhurst Organic Produce): How to create a resilient system (1.8MB)
The fact that we are facing a change of climate is clear to just about everybody, what is not clear is exactly what that change will be. There are many theories all based on various interpretations of scientific studies done over the past two decades, but as yet there is no universal scenario emerging. This makes planning our agricultural strategy for the future especially challenging. We need to be prepared for varying degrees of climatic pressures on our food production systems; changing an agricultural system is not something that can be done from one season to the next. So long term planning is needed, coupled with various contingency plans in case things do not work out the way we had hoped.
I would like to think that I would be possible for me to give a clear direction as to how we are to build resilience into our food production systems, but I am not able to, it will take a concerted effort for agriculturalists to come up with such plans. The organic producer I know is in a far better position to bring about a change to resilience but we are up against the GM lobby who think they can design their way out of trouble. GM is likely to be a far greater threat than climate change to the resilience of our agricultural systems, because it will lead to complacency and that is a very dangerous thing. What I will be presenting will be the possibilities that exist to develop robust systems able to resist difficult climatic conditions but still able to deliver an ample supply of food. This change will be based on a “systems approach” and will inevitably mean a very big change in the way we grow, harvest and distribute food in the future.