Farmers Weekly Magazine

Adapting water treatment technology to a farm setting could reduce slurry storage requirements by 10-15%, make better use of farm nutrients and produce an effluent that is suitable for discharge into watercourses.

Research (carried out as part of the Tywi Farm Nutrient Partnership) adapted, combined and repackaged technology typically used by water companies for removing water and capturing nutrients from slurry.

See also: New slurry tech for storage and handling benefits pig farm

Such an approach could be attractive to dairy farmers under pressure to limit nutrient loss and water pollution.

Policy changes in Wales mean farmers will have to give notice and submit an application to apply organic manures at 250kg N/ha for 2024 under the Enhanced Nutrient Management Approach.

After this time, the plan is to adopt a 170kg N/ha requirement, which could see some producers having to reduce stock numbers or take on more land to spread slurry.

Welsh slurry storage requirements are also set to increase to five months’ capacity from August 2024, bringing them in line with current requirements for English producers in nitrate vulnerable zones.

Neil Nicholas at the entry point of the reed bed © Aly Balsom

Pollution risk

About 90% of slurry is water. This water is the main source of pollution, through surface and groundwater run-off, says Neil Nicholas, research and development co-ordinator for Coleg Sir Gar in Carmarthenshire.

“De-watering” slurry splits the solids from the water, creating the potential to reduce storage requirements and improve nutrient management.

The system trialled by Coleg Sir Gar’s Agriculture Research Centre also looked at various methods of chemical treatment and filtration with the view to creating water of high enough quality that it could enter watercourses. 

Slurry de-watering and nutrient capture: How it works

• Slurry is pumped through a screw press separator and the coarse solids (fibre/bedding) are collected.
• The liquid then goes to a reaction tank where chemical water conditioners are added, with the aim of clumping together any dissolved solids.
• The first tank produces pin-prick sized solids. In the second tank, these are bound together through chemical reaction to produce “Rice Krispies”-sized solids.
• The material is pumped to a decanter centrifuge where the solids are split from the liquid through centrifugal action and filtration.
• The solids are collected and the liquid goes into a dissolved air flotation unit (DAF). This is typically used in wastewater plants to clean water. Compressed air and chemicals are introduced. Micro-bubbles form and attach to any remaining solids that rise to the surface as a “foam”. This can be skimmed off.
• The final liquid from the DAF moves to a balance tank before being pumped to a reed bed.
• The liquid is gravity fed through the system from entry point. The reed bed includes three channels divided into solid (pea gravel and reeds) and liquid cells.
• Some of the cells are oxygenated and some are deoxygenated. Aerobic bacteria in the oxygenated cells help convert ammonia to nitrite and nitrate (nitrification); anaerobic bacteria in the deoxygenated cells convert nitrate to nitrogen gas, which is released into the atmosphere.
• Bacteria on the gravel and reed roots make use of any remaining nutrients in the liquid to survive, grow and reproduce.
• The liquid is retained in the beds for 180 days.
• At this point, it is potentially of high enough quality to be pumped into watercourses.

The reed bed © Aly Balsom

Key findings

Neil runs through the key findings from the study:

1. Storage requirements

Removing the solids from the liquid reduced slurry storage requirements by 10-15%.

2. Nutrient management

The process produced a concentrated solid that could be easily stored and applied when needed.

This promotes more efficient use of nutrients, as farmers are not under pressure to spread slurry simply to manage slurry levels, which can lead to nutrient wastage and increased pollution risk.

3. Sward contamination

After five weeks, there was no significant difference in leaf contamination between ground that had received no nutrients and plots that had received the separated solids.

Cows could also graze a week after applying the solids, two weeks sooner than after slurry application.

4. Flexibility

At the point of solid/liquid separation in the decanter centrifuge (See “Slurry de-watering and nutrient capture: How it works”), the liquid fraction contained less total nitrogen than the 0.5kg/cu m permitted under the AHDB’s Nutrient Management Guide RB209 for “dirty water”.

Under current guidelines, this separated liquid could be spread all year round, alleviating pressure on slurry stores.

Solids could also be exported if not enough land was available. They could provide valuable nutrients for arable farms or be used in anaerobic digester plants.

5. Discharge into watercourses

Recent data indicated that the total nitrogen level in the treated water at the end of the process was below the 15mg/litre required to meet discharge consent limits.

So if a discharge licence was sought and approved, the water could enter watercourses.

The water at the end of the process, which should be clean enough to go into watercourses © Aly Balsom

Scope for commercial use

Neil says the system shows promise, but cost would prohibit uptake by many farmers. For a 250-cow herd, he estimates a cost of about £165,000, excluding the reed bed.

The reed bed used in the trial cost £140,000, but this could be cheaper if a farm did its own groundwork. Operating costs are about £15/cu m of slurry.

As an alternative, the process could be stopped after the decanter centrifuge stage, as this would produce a liquid that could be applied as dirty water.

This would save £60,000 on the cost of a dissolved air flotation unit and avoid the cost of the reed bed.

A three-phase electricity supply is also needed, plus a full-time operator to manage the system.

The dissolved air flotation unit © Aly Balsom

As a result, Neil sees the system having a role in:

Larger herds

The cost of the system makes it more relevant to herds of more than 500 cows. Larger equipment would be needed than that used at Coleg Sir Gar, which would be more expensive, but not double the cost.

Regional treatment facilities

A centralised treatment plant with a slurry dewatering system and biochar production would allow farmers to export excess slurry to a central hub.

Methane could be collected from a covered slurry lagoon, converted into fuel and used to power trucks to collect the slurry from farms.

After the de-watering and nutrient capture process at the hub, liquid could be discharged into watercourses and the solid processed into biochar.

Biochar is produced when organic matter is carbonised at high temperature in the absence of oxygen.

Neil says biochar has numerous benefits, including improving carbon sequestration when applied to land, and lowering methane emissions by 15-50% when used as a feed supplement for ruminants.

Fliegl has revived the Cargos forage wagon range deemed surplus to requirements by Claas.

There was little time for major design changes, with just six months separating the completion of the deal (September 2022) and the reopening of the production line (March 2023).

See also: Tips and advice for buying a used forage wagon

In fact, the only significant alteration is a new moveable front wall that has increased the standard capacity by 3cu m. This translates to an extra 6cu m when the load is compressed.

There is also a bigger 2.3m alternative to the Claas-derived 2m pick-up, which feeds crop through a 40-knife chopping bank.

The Cargos range includes three 8000-series models with capacities from 30 to 41.5sq m, and two in the 9000-series that are good for 44 and 50sq m.

We had our triennial general election last month, and voters delivered a clear rejection of left-wing policies.

With that came a crushing and humiliating defeat of the Labour Party, led until her resignation by Jacinda Adern.

Swept to power by a populist wave promised to bring “transformational” polices to our nation, and re-elected by Covid-induced fear and the dysfunction of the main opposition party, we had six years of promises, little delivery, an explosion of government debt, and a growing racial and social divide.

See also: Farmer Focus: Never have I felt so unvalued by British Sugar

About the author

David Clark

Farmer Focus writer

David Clark runs a 463ha fully irrigated mixed farm with his wife Jayne at Valetta, on the Canterbury Plains of New Zealand’s south island. He grows 400ha of cereals, pulses, forage and vegetable seed crops, runs 1,000 Romney breeding ewes and finishes 8,000 lambs annually.

From a primary sector point of view, we have seen policy and legislation developed in the silos of Wellington politics, and bureaucracy driven by ideological agendas without industry consultation.

The result has been unworkable, unachievable and impractical legislation that would torpedo the agricultural sector in this country.

The six years, in my view, would be best described in farming terms as “all hat and no cattle”.

Our National Party, which seemingly has become slightly right of centre, has gained 48 seats in what will be a 123 centre Parliament, and is led by prime minister elect Christopher Luxon.

They had an exceptionally strong result in the electorate seats, which make up half our parliament, with list seats delivering the remainder on a proportional of vote basis.

The Act Party, who run a market-led agenda and propose many economic reforms, gained 11 seats. This party are traditionally the coalition partner of National, and complement the more centrist views.

As National and Act fall short of a majority, they will require support from NZ First, who gained eight seats. They are led by the 40-year veteran of NZ politics, Winston Peters.

They proudly run a Nationalist policy agenda and as a Maori man himself, Peters is arguably very well placed to heal the racial divides facing our country.

Now that the electorate has entrusted the responsibility of leadership on these parties and individuals, the challenge is now theirs to deliver on expectations.

I am very optimistic. I believe we have elected exactly the government that we so desperately need, to get our nation back on track to a prosperous future for all.

Reiter has slimmed down its merger design for the latest Respiro R8 Compact, with a new chassis and shorter linkage being the primary contributors to a substantial 30% weight saving over the R9.

A slightly narrower working width allows it to cover a 6m bout when the two rear belts are working in the same direction to deposit material to one side, or up to 8m in central discharge mode. For comparison, figures for the bigger model are 7m and 9m.

See also: Grass merger options grow as farmers seek rake alternative

The speed and direction of the belt conveyors can be altered from the cab, and the swath width is adjustable from 50cm and 2m.

Other updates include a new suspension system and minor improvements to the 380mm-diameter, six-tine pick-up. About 100hp should be enough to pull it.

Continental might be best known for its tyres, but the firm has recently branched out by adding some nifty pieces of technology to its product offering.

One of the latest is the retrofit ProViu 360 camera system – which mounts to tractors and other farm equipment – giving drivers a 360deg view around the machine.

The idea being that it removes blind spots and reduces the risk of prangs.

See also: What to look for when buying and fitting a tractor dashcam

It uses four high dynamic range (HDR) cameras with wide-angle lenses, the images from which are combined using images a complex algorithm to offer a bird’s-eye view of the vehicle and its surroundings.

Through the in-cab screen, operators can alter the angle of view to suit the job they’re doing and make use of automatic pedestrian detection, which warns if there are any people near the machine.

The firm has also introduced some powerful NightViu LED working lights, which deliver an efficient 100 lumens/watt.

They come with outputs from 1,500 to 4,500 lumens, and there are models to suit a variety of lighting scenarios, from highly focused spots to wide-angle floodlighting.

Prolific flock genetics and skilful management have overcome setbacks to get a lowland sheep flock hitting budgets, three years after being established.

Farm manager Ben Smith says the accounts at North Falaknowe, Coldingham, on the Berwickshire coast, show upwards of 170% sold for the past two years.

Ben manages the farm for owner David Morrison (James Brown and Co), who farms 15 miles away at a hill farm called Middle Monynut.

Farm setup

North Falaknowe was bought by David in 2020, following the installation of 142.5MW of wind turbines at Middle Monynut.

These turbines form part of Community Windpower’s Aikengall II and IIa wind farms.

In January 2023, David bought another farm – Bogangreen – a mile from North Falaknowe.

This mainly arable farm grows 1,600 pigs on contracts and 200 Blackface ewes drafted from Middle Monynut, which Ben helps manage in a low-input outdoor lambing system.

“I am given a fairly free reign to manage North Falaknowe and make my own decisions,” explains Ben.

“The aim is to have money left to reinvest in the farm. This year, I budgeted at £90 a head and about 1.7 sold, which we have done.”

Ben Smith © MAG/Michael Priestley

System aims

With profit in mind, the aim at North Falaknowe is to expand to 750 Highlander ewes.

Replacements will be bred to the prolific Highlander ram, which is an Innovis composite that includes Finnsheep genetics.

Dry ewes are given the grass of lowest nutritional quality for a “negative flush”, to keep the scan at about 200% and avoid too many triplets.

Scanning at 200% means the commercial breeding ewes at North Falaknowe have produced 447kg/ha of liveweight lamb before cull ewes, wintering hoggs and cattle are considered.

The sheep run on grass, haylage and mineral lick buckets. Haylage is fed indoors from mid-December, and high-quality silage (11MJ/kg metabolisable energy, 12.4% crude protein) is fed in late gestation before lambing starts on 10 March.

Forage-based genetics and a weekly grazing rotation, achieved by running mobs of 300 sheep, mean that only pet lambs, triplets and very lean ewes are given concentrate feed.

Last year, this totalled 20t, and Ben is aiming at using only 10t this year through better use of forage.

But, while the flock has made a good return for the past two years, Ben explains there have been some major challenges to overcome.

Setback 1: Maedi visna

David bought 400 ewes at a local auction in September, two months after Ben was hired.

They appeared to be fit, but soon, some started losing condition and dying, and flock performance in 2021 was poor (see “Performance of sheep at North Falaknowe”).

Response:

• Two blood tests were done on groups of thin and wasting ewes, and 160 were found to be carrying the chronic wasting disease maedi visna (MV).
• The mixed flock of Cheviot gimmers, Texel crosses and Mules was culled.
• All lambs were fed hard to get them off the farm by September to ensure incoming replacement stock would not be infected. Wintering Blackface hoggs, which had not mixed with the infected sheep, were rushed home.
• MV-accredited sheep were bought in: 390 Aberfield crosses were sourced by Innovis in 2020, about 150 Highlander shearlings were bought from Kevin Stewart, Sharpitlaw, in 2021, and another 140 ewe lambs were bought in 2022.

Setback 2: Infrastructure 

The farm had previously run cattle, and had limited lambing capacity for about 300 ewes. There were no sheep feed barriers, and all the gates were designed for cattle.

Initially, this was not deemed an issue, as the intention was to outwinter all stock and lamb mostly outdoors.

However, the clay soils could not stand outwintering, and the exposed ridge the farm sits on would have made lambing difficult.

In addition, Covid lockdowns in 2020 delayed the delivery of steel to adapt the main building into a sheep shed.

In the end, the steel arrived two weeks before the lambing season of 2021.

This meant only half the flock could be housed to rest ground. Then, to compound the issue, Storm Arwen flattened two further sheds.

Response:

• In 2021, because of lack of space, single-bearing ewes and some fitter twins from the MV-infected flock were lambed outside from 1 April.
• Lambing date in 2022 was brought forward to 15 March to lamb mainly indoors and turn out quickly to grass that had been rested, by housing most sheep on haylage after Christmas. About 200 later lambers (singles and fit twins) lambed outside. Weather conditions allowed immediate turnout most of the spring.
• In 2023, with two sheds flattened by the storm, a shed at Bogangreen was used to house all stock from December, and all lambing took place indoors.
• A new 500-ewe sheep house with handling system was installed during the summer, and the plan is now to lamb everything at North Falaknowe.

Setback 3: Heavy, magnesium-locked farm

North Falaknowe was known to have heavy soils, but testing revealed a high magnesium level across the farm.

Response:

• A programme of ploughing compacted grassland is underway, with 10ha (24 acres) a year ploughed and drilled with arable, following an initial 20ha (49 acres) in 2022. Two years of barley are followed by herbal leys.
• Gypsum (calcium sulphate) is being applied to the soil at 5t/ha a year. This is to address the magnesium issue, improve the soil’s cation exchange capacity and help open the heavy soil structure.
• Trace elements, humic acid, and Bio-N (a microbial-based fertiliser designed to help plant root structure and nitrogen utilisation) are being applied to improve soil fertility and biology.
• Metabolic profiles are done through blood tests taken three weeks pre-lambing to check fat mobilisation, protein, and trace elements.
• A lick bucket is offered all year, supplying zinc, choline, biotin, selenium, fish oils and other trace elements. Lambs eat any ewe leftovers.
• To ensure other minerals are supplied, ewes get a mineral bolus one month before tupping, and lambs get one at weaning.

Setback 4: Cryptosporidiosis

A rise in mortality in newborn lambs this spring was caused by the parasitic infection cryptosporidiosis, which was traced to one field.

The impact was a drop in lambs sold a ewe to 173%. Ben estimates that without the infection, the flock would have sold 182%.

Response:

• Poor-doing lambs from the affected field were housed, given a glucose drench and an electrolyte in their milk replacer and returned to their mothers if/when they improved.
• In future, lambing fields will be chosen to ensure dry grazing if possible.