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User story: Making sense of slurry storage
Updating a slurry system to increase capacity and flexibility has offered wide ranging benefits for one Wiltshire dairy farmer. Jane Carley reports.
Investing in equipment to separate slurry into liquid fractions and solids has not only made muck handling easier for D. and R. Johnson and Son, but has also improved the quality of the end product so it is no longer waste, but can be used as a valuable fertiliser.
Tom Johnson, who runs a 140-cow dairy herd at Middle Farm, near Salisbury, with his wife and parents, says savings have been impressive.
He says: “Fertiliser costs have come down by about £3,000/year, equating to about £60-100/hectare since we have been applying separated slurry.
“I work closely with my agronomist and soil test regularly to ensure we are putting the correct rates on, but it is a lot more efficient than simply hauling it out with a muck spreader.”
Cattle are housed for four months of the year in two main cubicle houses, bedded on sawdust and with all feed passages under cover.
They receive a total mixed ration of grass, maize and wholecrop, as well as being parlour-fed and the 8,000- to 9,000-litre yield for Mueller is 60 per cent forage-based.
In 2018, Mr Johnson consulted local dealer T.H. White about updating his slurry handling system.
Mr Johnson says: “We had an old concrete ramp to push muck up into the spreader and we scraped into a reception pit leading to the lagoon, but with Nitrate Vulnerable Zone [NVZ] regulations coming into force to restrict spreading, we soon found we were lacking storage capacity.”
T.H. White specified a Bauer separator to remove solids from the slurry and make more of the lagoon’s capacity. The muck ramp was also removed and, instead, muck scraped over slats into a reception pit before pumping to the gantry-mounted separator.
Separated liquids are pumped into the existing lagoon and solids pushed into a clamp at the side of the lagoon; parlour washings are treated separately.
Removing solids from the slurry also means it can be applied more frequently with less risk of contaminating the sward.
Slurry is spread from the 1.5 million-litre capacity lagoon on the 135ha of farmland via the farm’s tanker.
In the next growing season, the plan is to improve the nitrogen uptake further by applying the slurry to the pastures using a Storth 7.5-metre dribble bar, putting it closer to the roots of the sward.
Mr Johnson says: “We have used a splash plate in the past, but our location is very windy and we want to improve the precision of the operation.
“Because we used to struggle for capacity, the pressure was to get the lagoon empty as soon as the NVZ window opened, but now applications can be more targeted after first cut silage and on the maize ground.”
The project was grant-aided by the Rural Development Programme for England Leader funding programme (now closed for new applications in advance of the UK leaving the EU) which covered 40 per cent of the investment. Plans for the scheme were drawn up by T.H. White’s Bob Gallop.
Speed
Mr Johnson says: “Getting grant funding was a big help and it is not an especially complex process. We filled out the forms and submitted the plans and it came together quite quickly.”
T.H. White offers back-up for the system and Mr Johnson says it is low maintenance, with only one grease point.
Checking the levels and keeping an eye out for foreign objects, which tend to be filtered out by the slats, are the other routine tasks.
Mr Johnson says: “The separator has also taken pressure off the other machinery as there is no need to push muck up a ramp.
“The system also fitted into our existing layout, so there was no requirement for building changes or planning permission.”
One benefit of the development is that the newfound lagoon capacity allows for potential expansion should the herd size expand, an option Mr Johnson is considering with space available in the cubicles and parlour for an extra 20-30 cows.
Tower
A further update may include the installation of a tower in the future, as the existing lagoon is not covered and rainfall can impact on capacity.
Divide and separate
T.H. White’s slurry specialist Bob Gallop explains how the system, based on Bauer pumps and equipment, works.
“Slurry in the lagoon is stirred with a 7.5kW wall-mounted Bauer MEX 305 mixer which has a 305mm diameter and 3.5-metre-long impeller.
“A Bauer CSP 5.5kW submersible pump with cutting disc then pumps it to the 5.5kW Bauer S655 separator, which has a stainless steel press screw and screen. The separator automatically splits slurry into liquid and solid fractions, using weight-regulated discharge.”
The system is controlled by ‘high and low level’ float switches, or can be set to work on a time clock from a Devizes Controls control box.
Mr Gallop says: “If operated in automatic mode from the control box, the system will start from the high float or the timer, first to run the mixer for a short time before the separator starts and finally the pump will supply the separator until either the low float or the timer stops all the motors.
“While in operation the mixer has its own timer to intermittently keep the pit mixed.”
The separator is suitable for herds of up to 200 cows, which would offer Mr Johnson scope for the expansion he is considering.
Cash in store for improvements
As part of the Agricultural Transition Plan, Defra will offer a new slurry investment scheme from 2022 to help reduce pollution from farming and contribute to the 25 Year Environment Plan and net zero commitments.
This is designed to help farmers prepare for more stringent enforcement of the rules around slurry management over the transition period.
This scheme will help farmers invest in new slurry stores which exceed current regulatory requirements and are proofed against higher standards expected in the future.
The scheme will also enable farmers to adopt other pollution-reducing measures, such as low emissions spreaders, which are to be a legal requirement by 2025, and the cost of storage capacity to go beyond the current legal requirements.
Funding will be given to meet a significant proportion of one-off capital cost of new stores and impermeable covers and to pay for a significant proportion of other associated equipment (pumps, pipework, access, reception tanks, etc).
Consultation on the scheme will take place in spring 2021 and details of how it will be rolled out published later in the year.
Defra expects to make funding available from autumn 2022/23. In addition, the Farming Investment Fund will include some slurry equipment from 2021.
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