Using Green Manures in Orchards

Emily McCoy
Friday, 12th August 2016

The Innovative Farmers Network have been experimenting with green manures in apple orchards. It has helped protect fallen apples, increased beneficial insects and improved soil conditions.

The health of soil, plant, animal and man is one and indivisible. Lady Eve Balfour, a founder and first president of the Soil Association1

95-99% of our food comes from the soil,2 yet globally we seem to have lost touch with this vital resource. Experts have estimated that we only have 100 harvests left. Permaculture seeks to maintain the balance between the cycles of earth and nature, but to avoid worldwide disaster we need to replicate this and urgently take action, at scale.

The Soil Association recently released a new document '7 Ways to Save Our Soils'3 which calls on British politicians, policy makers and farmers to readdress the health of soil. The document lays out seven simple ways to restore valuable soil organic matter to help improve the fertility of our soils.

Many organic farmers and growers are already using these and other methods that safeguard soil – but we must learn from these farmers and share this important knowledge with all farmers and growers. This is what Innovative Farmers sets out to do and field labs across the UK are linking farmers and growers with experts and researchers to trial different methods and find solutions to common farming problems that are easily practicable.

Green manures – one way to improve soils

Using green manures is one way farmers and growers can restore essential nutrients to the soil and rebuild soil structure. Green manures are made up of a variety of different annuals or herbaceous perennials like clover, mustard, chicory or sainfoin. They are commonly used as a key part of regenerative agriculture, along with minimum till, longer crop rotations, composting and mulching to restore nutrients to the soil. The higher cost of seeds for green manures can put farmers off so research into the best type, and the effects of different mixes, is hugely beneficial. Once established, green manures grow fast and outperform weeds with thick foliage. Longer, nitrogen fixing roots can help improve soil structure and when dug into the ground whilst still green they return valuable nutrients to the soil.

A group of Innovative Farmers in Hereford and Worcestershire looked at the use of green manures on an arable farm, and their use in an apple orchard. Different farms have different crops and different soils. Some may have stock, some may not. For this reason a range of research projects and field labs or trials were run, to analyse the effect of each kind of green manure.

Pershore College – looking at apple orchards

Apple orchards are one place where pesticide sprays could be reduced if a suitable alternative is found. Pershore College have one small area of organic espalier apples as well as several non-organic orchards. They wanted to find a way to improve soil quality where they struggled to enter the orchards to cultivate. Pershore are also keen to encourage more pollinators and predatory insects into the orchard. Field labs were set up in two of the larger non-organic orchards at Pershore – Huxley and Sunnyside in 2014-15.

In each orchard different green manures were sown in the grassland strips between the rows. The strips were first disced over to cut through the sward, over-seeded with a spinner and rolled to press the seed in. Theses single species green manures were tested in Huxley orchard:

White clover

Red clover

Persian clover

Lucerne

Yellow trefoil

Sainfoin

At Sunnyside orchard single species and two mixed green manures were tested:

Chicory

Mustard

Crimson clover

Humus builder Soil Structure Improver 2-4 year mix (red clover, chicory, and cocksfoot)

Herbal over seeding mixture (red clover, white clover, alsike clover, birdsfoot trefoil, sainfoin, sweet clover, chicory, burnet, yarrow, sheep’s parsley, and plantain)

Soil texture in both orchards is silty clay loam (pH 6.3). Organic matter content of soil from both orchards has been tested – Huxley 5.8%, Sunnyside 5.4%.

The different green manure crops were assessed by how easy they were to establish as well as their soil conditioning effects, water retention, nutrient supply, and amount of routine maintenance required.

Chicory%20root.JPG

Clover roots dig deep for nutrients

Limitations

Topping the green manures adds to maintenance, but to reduce the workload this can be left until they reach 50-75cm, as long as the underlying grass and weeds don’t go to seed. Before apple harvest the green manure needs to be topped to 20-30cm.

In apple orchards the green manures must be low maintenance to avoid root damage. There were some problems with loading fresh green toppings from the green manure against the base of the fruit trees: a thick layer of damp mulch can lead to collar and/or crown rot and the growth of extra roots. As the mulch breaks down the roots are exposed and need more mulch or compost, and the cycle begins again. However, this could be solved by applying a lighter layer of mulch.

Field lab results

Growing perennial clover/legume mixes instead of single species annuals seems to be better for soil organic matter, nitrogen fixing, and pollinators. Grass in the mix helps to use the nitrogen that the clovers fix. In the orchards, Robin Bickley from Pershore College noted that a horse paddock mix (Cotswold Seeds do a mix including ryegrass, fescue and timothy) was particularly beneficial. It didn’t grow quite as ferociously as other mixes, and therefore didn’t require as much management, whilst maintaining the benefits.

Robin commented; “There was a very mixed group, from all backgrounds and the problems I had were very different from some of the farmers who were planting green manures at field scale on an arable farm. We all learned something different from everybody’s problems and experiences – especially the value of getting a green manure established – treating it as a crop rather than just sticking it in the ground over winter.”

The green manures offered an opportunity to avoid damage during apple harvest. Usually the orchards would be sprayed pre-harvest, leaving ground exposed. In bad weather this can result in apples being harvested in mud. Green manures present a useful tool to aid this.

In addition, there are other benefits of letting green manures flower and set seed, notably that this is good for pollinators, but also that it can also help maintain continuous ground cover, protecting the orchard soils (one of the 7 Ways to Save Our Soils). 

One farmer involved in the field lab said; “Every opportunity to plant a green manure/cover crop should be taken, but some may only have marginal benefit. In the end it all boils down to what suits your farming system.”

Further information

The Soil Association works to share more sustainable farming techniques with farmers, growers, researchers and policy makers. To find out how you can help go to: www.soilassociation.org/supportourwork

Innovative Farmers is a not-for-profit network giving farmers research support and funding on their own terms. Many of the best ideas in farming come from farmers. But most research happens off-farm. Innovative Farmers changes that. It helps farmers find lasting solutions to practical problems, from managing weeds and pests with fewer chemicals to testing more sustainable animal feeds through on-farm field labs. Together farmers are finding new ways to grow better food, cut waste and pollution, and protect their farm from volatility. It is part of the Duchy Future Farming Programme, funded by the Prince of Wales’s Charitable Foundation and backed by Waitrose. To find out more about Innovative Farmer field labs: www.innovativefarmers.org

The Soil Association was founded in 1946 by farmers, scientists, doctors and nutritionists to promote the connection between the health of the soil, food, animals, people and the environment. Today the Soil Association is the UK’s leading membership charity campaigning for healthy, humane and sustainable food, farming and land use. Its Chief Executive is Helen Browning, and Chair of Trustees is Dennis Overton.

standards internationally, delivering assurances of quality and provenance that industry and consumers can trust. Its Chief Executive is Martin Sawyer and its independent board is chaired by Nick Buckland. To find out more visit www.soilassociation.org

1 Lady Eve Balfour (1943) The Living Soil, Faber and Faber
2 Save our Soils/ Fao facts http://saveoursoils.com/userfiles/downloads/1423729537-Save%20our%20Soils%20Toolkit%20-%20ENG.pdf
 Pimental D. (2006) ‘Soil Erosion: A food and Environment Threat,Environment, Development and Sustainability, 8: 119-137

3 www.soilassociation.org/Portals/0/pdf/7WaysFinal.pdf

Further resources

Using perennial polycultures to create mulches and fertilizers

How to grow your own mulch

Growing mulch for a farm

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