Complying with new nitrate vulnerable zone rules could be a costly process. Peter Chapman gets some expert advice on what the new rules mean for Thornton Grange Farm. Wendy Short reports

Slurry storage

The new NVZ rules will require farms to provide sufficient storage facilities to store all slurry produced by livestock during a period of five months for cattle (October to February). Producers have three years from 1 Jan 2009 to comply with the new storage requirements.

All-bar 20 acres of Thornton Grange falls within an NVZ and Mr Chapman’s estimate that the farm would need about five times more slurry storage to comply with the new NVZ rules was right on target, after he called in Fieldfare Associates consultant, Peter Hoey to verify the figures (table 1).

The existing slurry system can hold 490cu m, about one month’s production over winter. Extra storage is, therefore, top of the agenda for Mr Chapman, who has decided that building a lagoon will be the cheapest option to cope with his expanding dairy herd.

Slurry 1

But the process is proving to be more complicated than he imagined. “Building a lagoon is not just a matter of hiring a JCB and digging a big hole,” Mr Hoey says. “It has to be properly designed and engineered.”

Mr Chapman has already identified a fairly level piece of land close to the cubicle housing as the site for the new lagoon, but he needs to block or divert field drains in the area. Total cost is still unknown, as he is waiting on suitable designs and quotes.

“My main concern is to make sure I’m fully prepared before I start work on the lagoon. The Environment Agency (EA) has a number of specific requirements, and it would be a terrible waste of money if I had to make any changes after completion. I will need additional expert help before finalising the design.”

Working with Mr Hoey, he has established an action plan, to take the lagoon development to the next stage:

• Source an experienced lagoon designer.

• Arrange comprehensive soil testing on the proposed lagoon site, to establish clay content/permeability.

• Send manure samples to a laboratory, having followed sampling protocols in the new NVZ guidance leaflets (or RB209).

• Analyse “dirty water” (which has no requirement for storage) routinely during autumn/winter/spring, to prove it has a low nitrogen content.

• Make risk assessment maps for manure spreading on individual fields.

New slurry store building tips

  • Reception pits must have capacity to take two days’ slurry production, plus rainfall
  • The proposed lagoon will need 750mm freeboard. This is headroom, above which the store must not be filled
  • Lagoons should be built to British Standard 5502 and the CIRIA (Construction Industry Research and Information Association) construction specification (report 126)
  •  The EA must be notified two weeks before any new slurry stores or silage effluent tanks are brought into operation. Mr Chapman will need to have documentation signed off by the lagoon designer. But the farmer, as operator, is held responsible for any pollution incidents
  •  If an EA representative perceives that the new installation(s) pose any threat to the environment, a warning will be issued to rectify the problem. Failure to remedy may lead to prosecution
  •  The EA may also ask producers about contingency planning. A plan should be drawn up, showing how the farm would cope with a slurry pump break down, for example

Dirty water management

Under the new rules dirty water can be irrigated on to land at any time of year, if a risk assessment is carried out and ground conditions are suitable, says Mr Hoey. No storage is required if the liquid comes from lightly fouled concrete yards or from the parlour, if it is collected separately.

At Thornton Grange, slurry in the cubicle house is moved via automatic scrapers to a reception pit (capacity 50cu m), and then pumped into an above-ground tank with a 450cu m capacity.

Slurry 2

Youngstock and dry cows are on straw, although they have loafing areas that are scraped out by tractor. Slurry from the collecting yard goes into the main reception pit, along with parlour washings, which dilute the slurry for easier handling.

Silo run-off and silage effluent goes into a separate tank, and is removed by tanker in summer, or diverted to the dirty water system over winter. Dirty yard rainwater and parlour plant washings are spread via a low-rate irrigator (equipment that has a low spreading trajectory will be allowed under the new rules).

Mr Hoey suggests DEFRA’s RB209 fertiliser recommendation book should be used as a guideline for the classification of “dirty water”. It is described as being less than 1% dry matter and containing less than 0.3kg/cu m of nitrogen. The definition of slurries includes nitrogen-rich liquids from weeping-wall stores, strainer boxes, slurry separators or silage effluent tanks.

Mr Chapman says that installing a separator would reduce the slurry storage requirement at Thornton Grange by about 20%, but he is not keen on the idea. “A modern separator with an auger would cost £25,000-30,000. I can’t justify this level of expenditure if it only partially tackles the problem.

“I have just over three years to come up with the required storage capacity. It sounds a long time, but I have only recently had the expense of building a new parlour and putting up another building,” he adds.

Whole-farm nitrogen allowance

The new rules set a limit of 170 kg/ha of total nitrogen from livestock manures (deposited during grazing and by spreading) per calendar year, averaged across the farmed area.

At Thornton Grange, the whole-farm allowance is 28,560kg of nitrogen. The livestock produce 25,705kg, which falls within the limit. But once the herd has reached its target size of 220 cows, nitrogen production will rise to 29,930kg, creating more than 1370kg. This is the equivalent of 457cu m of slurry (1370kg of N divided by 3kg of N, to give a figure in cubic metres).

Slurry 3

Butt his level of excess is unlikely to cause a problem, as Mr Chapman could transfer slurry to a neighbouring arable holding or send heifers elsewhere for rearing.

Mr Hoey predicts that some farms will be permitted to have a whole-farm manure N limit higher than 170kg/ha, but believes this will only cover cattle producers with 80% of their farm in grass. Permission for higher stocking rates will probably come with conditions attached, he adds.

Closed periods (organic manures)

The spreading of organic manures with high available nitrogen content will be prohibited during specified periods under the new rules. The length of the closed periods ranges from 3-5 months and applies to all soil types, not just shallow or sandy soil.

Farmers who do not have sufficient manure storage to comply with the minimum storage requirements and closed periods, must provide extra storage by 1 January 2012. Mr Chapman will use this leeway to complete new storage facilities.

Why not put your NVZ questions to DEFRA? Visit http://www.fwi.co.uk/community/forums/put-your-nvz-questions-to-defra-here-23084.aspx

Thornton Grange Farm

  • Where: Thornton Village, Middlesbrough, Cleveland, a 167ha (415-acre) rented dairy and arable unit run by Peter Chapman
  • Land: Most is ring-fenced and rented from one private landlord. The soil is a fairly heavy, deep clay
  • Cropping: About 97ha (240 acres) of grass are rotated with 70ha (175 acres) of wheat, maize and set-aside. Oilseed rape is sometimes grown as a break crop
  • Livestock: Thornton Grange supports 168 mainly commercial Holstein Friesians averaging 7850 litres a cow. Calving is all year round and milk is sold to Arla. The business is on course to move up to 220 cows over the next few years.
  • Staff: Peter and his wife, Jane, manage the farm with help from one full-time worker
  • Environment: The farm has been in Countryside Stewardship since 2000, and entered into an ELS agreement February 2006.
  • More information on Thornton Grange Farm 
  • More information on other Management Matter farms

Table 1: Thornton Grange slurry storage requirement
(based on undiluted slurry)

Livestock unit

Volume per livestock unit/month (m3)*

Number cattle

Total volume/month (m3)

Dairy Cow
(650 kg)

1.93**

220

424.60

Dairy heifer replacement
(+24 months)

0.98

20

19.60

12-24 months
(400 kg)

0.79

75

59.25

Young cattle
(6-12 months)

0.40

35

14.00

Calf (up to six months)

0.21

35

7.35

*Information taken from the DEFRA booklet (PDF)
Manure Planning in NVZs – England
 
**1.93 (equivalent to 64 litres a cow a day)

Table 2: Milk production figures (12-month rolling)

Margin over purchased feed

£1,390 a cow

Feed cost/litre

7.2p

Feed kgs/litre

0.31

Milk value/cow

£1,920

Rolling average milk price (p/litre)

25.3