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On Friday the 8th July, the farm walk with Iain Tolhurst from Tolhurst organic was held in glorious sunshine. Iain had been awarded runner up in our Soil Farmer of the Year competition due to his commitment to soil management and his innovative approach to maintaining soil fertility and his use of rotations and green manures.
After the presentation of Iain’s award, and an amazing lunch, the tour began.
The walk started in the walled garden, which is focussed on small area cropping, including growing carrots and beans. The veg are supplied to local customers and the crops are grown on a 9 year rotation. Alongside the walled garden are the greenhouses and tunnels.
The tunnels are cropped very intensively, often producing 3 crops per year, to provide a continuity of production for the business and to reduce the ‘hungry gap’ which is so often a problem time in vegetable growing. The greenhouses and tunnels work on a 5 year rotation with woodchip compost being used to maintain soil fertility. The greenhouse is used for raising plants, which are raised using their own potting compost, the business gave up using peat based compost 20 years ago and developed their own plant raising system.
Vegetables are sold direct to the consumer through a box scheme, and the farm produces 100 tonnes of food, over 100 types of vegetables and usually 300 different varieties and sowings per year. All this equates to an intensive output business with the aspiration to make the farm self-sufficient.
The foundation behind this is the soil and how we look after it. The situation here is that we have to grow a wide range of crops in one soil type.
In the garden the rotation is long, there are no livestock inputs, fertility is built using green manures, and these green manures are fundamentally important, as nothing gets taken. The rotation has been designed to allow periods of fertility building within it.
At any one time, 65% of the land is cropped and 35% is growing green manures.
The green manures are also important to protect the soil, Iain explains, “one of the biggest losses of soil nutrient is winter rain, so by growing green manures and not leaving the land bare that nutrient is preserved for the next crop. The nutrient is overwintered in the plant where it is held, rather than washed out in the soil. This means that we don’t have to bring lots of nutrients in from outside.”
The green manures also encourage the soil biology and micro-fauna to work, making nutrients available for the plants.
“To manage soil you have to look at the whole farm.
Soil is integral to everything that we do.
We’ve made mistakes along the way, that’s how you learn, but
at the root of everything is the health and fertility of our soil and how we are going to look after it.”
“We are not growing crops, we are growing biodiversity either in terms of encouraging wildlife, but also soil biodiversity and providing the building blocks for life in the soil to thrive.”
The aim of our soil management is to maintain our soil organic matter levels which in horticulture is difficult as it has big demands on the soil and is an intensive system. We are happy with the fact that we are managing to build soil organic matter levels each year, which is incredible challenging in our system.
However we are also mindful of the fact that although we are managing to build up this soil organic matter, that organic matter can be lost incredibly quickly.
We are very conscious of the fragility of what we do."
The business hosts numerous research projects each year, looking at different aspects of the farm including biodiversity, soil structure and organic matter, as well as analysis. One of the benefits of being open to this research, is that it has provided a lot of data to draw from, including soil pH, P, K and micro elements as well as the carbon sequestration in the soil.
The soil type is a sandy clay loam with a high stone content (as high as 40-50% stone in some parts). The advantage of this is that the soil is very free draining, and warms up quickly, and the soil is quite forgiving. The fields were in a very poor state when they arrived, and fertility has been built through the use of green manures and composts.
The group then moved onto the field and started at the woodchip compost pile. The compost is never applied to bare soil, only to green manures. It is applied in this way to break down on the surface, how you use the compost is very important.
“It’s not just how you make the compost, it’s how you apply it.”
Iain continues, “When the compost is applied, you’re not just adding organic matter, your adding bacteria and fungi in the form of biology which allows you to add life to your soil, to work for you, in unlocking nutrients, controlling pests and diseases and maintaining soil health.”
The group went to look at the different aspects and crops of the 7 year rotation that is used out in the field which follows the pattern below:
Year 1 and 2 – Red clover / Lucerne / herbs (4-8 varieties) – Cut and mulched, compost applied 50 cubic metres per hectare, 2-3 applications mid-summer and autumn.
The fertility building crops are the most important crops that are grown on the farm, they need to fix the nutrients for the next crops and leave enough fertility behind. The idea is to maintain fertility throughout the rotation and safeguard the soil structure. The over wintered green manures protect the soil structure over the winter as well as holding the nutrients.
Year 3 – Potatoes, with overwintered green manure (clover / vetch / ryegrass, if sown by mid-September, cereal rye for later sowing.) Sweetcorn undersown overwinter with green manures.
Year 4 – Brassicas, winter / spring cropping, possible under-sow clover / vetch early September.
Year 5 – Allium. Onion and leeks, Onion is intercropped with clover and yellow trefoil. Leeks are undersown with cereal rye / oats / vetch. Post onion sown crimson red clover / vetch.
Diseases such as onion white rot are controlled through the rotation. The brassicas that are grown previously suppress the diseases in the soil due to their bio fumigation properties. Once these are turned in, it minimises the risks from white rot.
Year 6 – Carrot after leek, parsnip after onion. Beetroot / chard late July, undersown overwinter with green manures. Broad beans sown October.
Year 7 – Broad beans Feb / March, sweetcorn and squash. All crops undersown with red clover / Lucerne.
As such, 30% of the field is in long term green manures (years 1 and 2 of the rotation), while the other 70% is being cropped for vegetables. As well as this, within the vegetable crops there is 30% of the field that is growing over wintered green manures and 30% is undersown with green manures.
The result is fields that are growing 100% biodiversity, the aim of the farm.
As well as the veg, Tolly is trialling an agro-forestry system in one of his fields. The trees provide numerous benefits including a reduction in wind speed as most of his veg crops don’t like the wind, they increase biodiversity, increase associations with mycorrhizae and there is the possibility of production from the trees themselves. As well as this, they are trialling out different crops directly underneath the trees including daffodils, rhubarb and artichokes. The potential negatives from the system is a loss of land for cropping, but he is hopeful that the benefits will outweigh the negatives.
The long term vision is that there is potential with the agroforestry system to also produce their own woodchip to make into compost.
In terms of cultivation on-farm, the plough is still used here. Tolly considers that the best way to get the green manure crop in is to plough them, and a power harrow is used to create a good tilth.
“In horticulture you inherently need to move a lot of soil”
Tolly has been working on this system for decades, and has focused a lot on trying to get things right in the soil. After doing all this stuff for over 10 years, he is now beginning to see the benefits, and reaping the rewards in terms of resilience. He explains further,
“You can’t underestimate the importance of resilience, and building the resilience into the soil, however it takes time to develop, it’s not a quick fix, and some faith is needed that you will get somewhere better than where you are now.”