Herts grower shares experience with Johnson-Su bioreactor – Farmers Weekly

A source of protozoa and nematodes, the extract from a US-invented composter is part of one Hertfordshire grower’s five-year plan to improve soil biology and cut costs.

Richard Blair, with his son Olly, manage 300ha of arable cropping on the family farm near Redbourn.

However, the loss of the Basic Payment Scheme (BPS) has prompted changes to the system at Flamsteadbury Farm with the eventual aim of direct-drilling and bringing second wheats back once the soil biology has been improved.

A blackgrass problem had seen second wheat dropped from the rotation, a shift towards spring cropping (currently two-thirds of the area) and delayed wheat drilling.

Delayed drilling brings increased risks if the weather turns, as seen last autumn, and not getting a crop in the ground. “However, we had the BPS payment acting as a cushion and you could take that gamble.”

With BPS being phased out, he realised that they needed to change direction.

So Richard spent time reading books such as Gabe Brown’s Dirt to Soil, and watching experts on YouTube videos to gain knowledge.

Last winter, he went on a Hutchinsons soil course – all to gain an understanding of soil biology.

Armed with this knowledge, with the help of his Farmacy agronomist, he has put together a five-year plan to improve soil health.

This is through the use of cover crops, adding muck, introducing livestock and reducing cultivations.

The aim is to get biology working – so that he can reduce crop inputs while maintaining crop yields. He believes he can cut variable costs by £100/ha over the next two to three years.

He recalls the benefits when moving from ploughing to min-till, and hopes to see similar benefits by going the next step to no-till.

A key part of improving soil health is the compost produced by a Johnson-Su bioreactor.

While they are very cheap to build, there is still a cost as the tea also requires 10 litres/ha of fish hydrolysate, which costs £9.80/ha, and molasses that acts as the energy source at 10 litres/ha, which comes to £7.10.

There is also the investment needed for the tank on the front of the drilling tractor plus associated equipment – which he estimates is about £40,000-50,000.

However, the closure of the Sustainable Farming Incentive scheme has held things back as that income was earmarked to help fund the transition. He is hoping to secure private funding to enable the next stage.

Two years ago, they built two Johnson-Su bioreactors after reading a Farmers Weekly article. One for the autumn-sown cropping and the second for the spring crops, as it can take up to 350-400 days to produce the compost.

After some trial and error, the current starter mix is 25% horse manure (mix of fresh and well rotted) along with maize, fresh grass and a bit of hay.

They started with fresh hay, but are now using stale hay to help get the heat up – as the aim is to reach 60C, which is achieved in the first two to three days.

Then they have to wait until the mix gets back to 30C before adding the worms. This generally takes two to three weeks. About 60 worms are added in each container – a mix of different species collected from the fields.

The mix is then left and they are aiming for about 200kg of compost, which takes about 300-350 days.

This amount covers 200ha, at a rate of 1kg/ha. For autumn sowings, that covers 100ha of wheat plus 100ha of cover crop. The second bioreactor is needed for the 200ha of spring cropping.

Water is then added to the compost to put it in a liquid form and a tea is made with the addition of fish hydrolysate and molasses.

Farmacy head of soil services Jade Prince says one key limitation is that once biological feed is added it needs to be used within six hours when applying it to the soil on the drill.

Richard is also looking at seed priming too, as this has a longer shelf life. This is where the tea is used to coat the seed at a rate of 2-3kg/t of seed along with 2 litres/t of fish and 2 litres/t of molasses.

They have done a trial batch of cover crop seed using a cement mixer and it was drilled this August.

The seed had a slightly different colour, but it absorbed it OK and there was no problem with the drill. Likewise, the beans soaked up the liquid.

Jade points out that some other growers have had problems where the seed was coated with an excessive amount of liquid. Over wetting the seed can lead to seed bunging up drills or potentially germinating in the bag.

Richard plans to drill his first crops using the extract next spring, once all the practicalities have been ironed out.

One of these is having a mixer big enough to prime the seed. He is looking at acquiring a pan-mixer, as that would do half tonne batches and would be two to three days of work to treat the 55t of seed used.

“We are looking at the logistics and extra workload, especially as we will also need to switch to home-saving seed.”

Extra shed space will be needed to store the treated seed and he is planning to trial how long it can be stored by carrying out germination tests over time.

• Have 30ha of cover crop and trial grazing with sheep this autumn. Aim is to extend cover cropping over 100ha and establish with Johnson-Su extract
• Combination of cover crops and muck to build soil organic matter. Currently 3-3.5%, aim to get to 5-6% over the years
• Reduce cultivations and eventually go no-till
• Have the flexibility of using Johnson-Su extract either applied to soil at drilling or priming seed
• Increase wheat area by reintroducing second wheats grown with a companion crop and established using Johnson-Su extract.

The aim is to inoculate soils with beneficial nematodes and protozoa, which then release nutrients contained in existing bacteria to soil fungi and crops.

Farmacy head of soil services Jade Prince says that if you look at typical arable soils with a microscope, there will be lots of bacteria, maybe a few fungi and the occasional protozoa.

With soil under hedges, you may see more protozoa and this is what you want to achieve out in the field. That’s because they feed on the bacteria and release the excess nitrogen that plants can use.

Looking at the compost, there will mix of amoeba, ciliates and flagellates – you want an even distribution of all three types of protozoa. By inoculating soil with this diverse, protozoa-rich compost, farmers can improve soil health, nutrient availability, and overall soil ecosystem function.

While there are some products available removing the need for a bioreactor, she points out that the extract can contain thousands of different species compared with the most complex off-the-shelf product which only has only eight different species.

Furthermore, the Johnson-Su extract is more adapted to the particular farm and its system.

This inoculation needs repeating each year, as farming practices will see numbers dwindle over time. “Farmers will need to keep topping up with protozoa.”

Jade has quite a few clients using Johnson-Su extract.

Flamsteadbury Farm, Herts

• Medium soils with flints over chalk
• 20% clay, 55-60% silt and 15% sand
• 300ha of crops
• One-third first wheat (Extase), one-third spring malting barley and rest split between peas and spring milling oats