Making and using compost to improve soil health has become a central part of the route Ken Hill Farm & Estate, near Snettisham in west Norfolk, is taking to transition to an organic farm.

Farm manager Nick Padwick took over management of the 1,400ha estate in 2018. At that time, it was a largely conventionally managed farm, albeit with a nature-friendly bias.

“We then started focusing on a strategy to change the farming system in a period where Basic Payment Scheme payments were reducing, and to address reducing biodiversity,” Nick says.

See also: How home-made compost improves soil health for two farms

Alongside some quite radical restructuring that saw low-performing arable land converted into either wood pasture within a higher tier Countryside Stewardship agreement, or environmental habitat corridors, he started farming the remaining arable land using regenerative farming principles.

Implementing that system always came back to one thing, he says: “Our soil.”

Soil test frustrations

After becoming frustrated with conventional soil tests, concerned about the gap between sampling, laboratory testing and receiving the results, and feeling they did not provide the information nor the accuracy he desired to understand the biological activity in his soil, he turned to Dr Elaine Ingham’s Soil Food Web School (see panels).

Having completed the foundation course – learning to use a microscope to assess soil biology and later achieving consultant training programme certification – Nick is putting his new knowledge into practice on the farm, as well as offering consultancy through Wild Soils.

Nick Padwick © Mike Abram

The aim on farm is to create a soil ecosystem that is dominated by beneficial fungi, bacteria, protozoa and nematodes, with a balance of bacteria and fungi.

At the start of the process, like the majority of the 400 soils samples he has analysed from other farms over the past two years, his soils were bacterial dominant, with low protozoa and fungi counts. “I also had very poor water infiltration.”

Some of his fields have soils that are still in that situation, highlighting that it is not going to be a quick fix. “But we’re working on it,” he says. “That’s the aim.”

Two tools

The basic tools he is using are the microscope to regularly monitor levels of biology in the soil, which he can then use to adjust the composition of his other main tool – compost.

Nick started making compost on a relatively small scale, filling circular towers made of wire mesh that stand about 1-1.5m tall with a 1m diameter, before scaling up to windrows.

Both still have their uses – the towers for making strong compost extracts suitable for use on seed when drilling, and the windrows for higher volumes for use on broad acres.

The recipe for making composting is critical, he stresses.

High-nitrogen material with a carbon-to-nitrogen ratio of 8-20:1 is needed to fuel microbial growth and decomposition in the compost pile.

Typically, depending on time of year, 10-20% of high-N material should be used, Nick suggests, with more needed if making compost in the autumn to aid heat generation, while lower amounts are required in the spring.

A further 30-40% will typically be green material, with a C:N ratio above 20:1, with the balance brown woody material.

Nick uses woodchip, preferably hardwood, that has sat outside for at least six months after being sourced from on-site management of the woodland areas of the estate.

Foraging clover understories and herbal leys, grown within Sustainable Farming Incentive/Countryside Stewardship schemes, have also proved to be a good source of high-nitrogen and green material.

“I’ve planted the herbal ley so that it is clover or nitrogen dominant, with some grasses, so I hopefully get the right diversity of green and high-N material in the windrow,” he explains.

Windrows are made by first layering woodchips, followed by the green/high-N material. “We lay it out in a way the compost turner can come through,” he says. “It’s important at this stage to put on enough water, so our compost turner has two IBCs with a pump with which we apply water when we do our first mixing turn.”

The base material is usually mixed twice initially, with water content judged to be optimal when two drops of water can be squeezed out of a handful. “We’re putting on anywhere between 20-100 litres/m of water on windrows that are 250m long.”

© Mike Abram

Temperature monitoring

A spreadsheet is used to record temperatures and moisture every 24 hours, with Nick taking three readings from the hot centre via both sides and the top. “It’s so important to understand the temperature and how long until it needs turning,” he stresses.

Specific temperature ranges and corresponding turning intervals are used to manage the process (see box). Temperatures above 55C are required to kill pathogens and destroy weed seeds.

Once the compost is mature, Nick either spreads it, as made, at roughly 5t/ha, or creates extracts to use through the season, applied in a custom-built Tow and Fert sprayer with a perforated basket that takes about 200kg of compost.

“The basket drops into the tank, like a cartridge going in a slot, and then water flows through the compost, spinning it around,” he explains.

“All the goodies come out of the compost and into the water. When I take the basket out after putting 4,000 litres of water in, I end up with washed woodchips. It has made an extract that I’m able to apply at 400l/ha using 13mm nozzles.

“At 10ha/load, I can treat 150ha/day – it’s game-changing compared with the 15ha/day I could do when making extracts from compost towers.”

While it is relatively early days, Nick believes the system is already “moving the dial”. Soil analyses are showing improvements in fungal biomass and protozoa numbers, while the fungi-to-bacteria ratio is moving closer to his 1:1 desired ratio, with tests in May showing a ratio of 0.6:1, compared with 0.01:1 a year earlier.

“We’ve certainly seen a change in our soils,” he says.

Whether that manifests in crop performance will be tested in the coming season with replicated trials. But he is hopeful, following a spring barley crop produced to organic guidelines that received four applications of extract and yielded about 5t/ha. “That was encouraging,” he concludes.

• Information for this article was gathered at an Unlocking the Power of Soil day organised by Soil Ecology Laboratory in Norfolk

What is the Soil Food Web?

The Soil Food Web is a complex and interconnected network of organisms that play a crucial role in maintaining soil health, plant growth and overall ecosystem function.

Championed by American soil biology researcher Dr Elaine Ingham, the soil food web encompasses a vast array of living things, from microscopic bacteria and fungi to larger organisms including nematodes, protozoa, arthropods and earthworms.

Dr Elaine Ingham © Mike Abram

As primary producers, plants form the base of the soil food web, harnessing energy from sunlight through photosynthesis, converting it into organic compounds and releasing exudates from their roots which, along with soil organic matter, provide food for soil microbes.

Bacteria and fungi in the soil act as the primary decomposers within the soil food web, releasing nutrients back to plants. Different bacteria and fungi species specialise in decomposing different types of organic matter, contributing to the overall diversity and resilience of soils.

Various organisms, such as nematodes and protozoa, consume bacteria, fungi and other organisms, regulating populations and nutrient cycling, and in turn these are eaten by higher level predators such as arthropods and larger nematodes.

The soil food web is characterised by symbiotic relationships, where different organisms benefit from each other’s presence. The interactions can also help explain nutrient cycling, disease suppression and soil structuring.

But human activities, such as tillage, pesticide and fertiliser application, disrupt the delicate balance of the soil food web, reducing microbial diversity, disrupting nutrient cycling and negatively impacting soil health and structure.