New Slurry Calculator

Published 1 October 08

New slurry calculator

Dairy farmers facing stringent new slurry storage requirements under proposed Nitrate Vulnerable Zone (NVZ) rules could benefit from a new slurry calculator program.

The Slurry wizard, developed for DairyCo, enables farmers to work out their slurry storage requirements, and weigh up the cost benefits of different ways to tackle under-capacity.

"The revision of the NVZs in England could affect up to 70% of dairy farms," says Andy Dodd, DairyCo extension officer. "Slurry production is a major issue on most dairy farms due to the high cost of providing storage and the cost of spreading.

"However, it is important as a source of nutrients with an average value of £78 per cow each year. With the cost of fertiliser rising there is an obvious cost saving opportunity where slurry can be used effectively."

Under the new NVZ proposals, farmers will not be allowed to spread slurry for up to five months of the year. They will also need 22 weeks' storage capacity, including provision for all dirty water which enters the slurry store.

Solid, stackable farmyard manure can be stored elsewhere and will not be subject to the closed spreading period. However, it is likely that total manure nitrogen production will be limited to 170kg/ha averaged over the whole farm, leaving some intensive producers facing having to take on more land or reduce stock numbers, says Andy.

Many producers do not currently have sufficient slurry storage to comply with these proposed new rules, he adds. They will therefore have to invest heavily in new capacity, or reduce the amount of slurry produced.

"This is where the Slurry Wizard can really help. It's a tool to help you calculate the amount of slurry produced from your livestock, how much storage you need, and how much land you need to spread it over. It can also recommend cost-effective solutions where your existing capacity is not sufficient for your needs."

Producers input farm-specific data like livestock numbers, farm area, water costs and usage, existing storage capacity and yard areas. Monthly rainfall is calculated from their telephone area code - or can be inputted manually. The Wizard then works out exactly how much slurry is produced each month, and highlights any problem areas of under-capacity.

"It then makes recommendations like covering yard areas, diverting and collecting clean water, installing a separator, or increasing your storage capacity," says Andy. "These will be specific to each individual farm - but in the main it is more expensive to build slurry stores than it is to divert clean water, so for most farmers the aim should be to minimise the amount to be stored. That also reduces the cost of spreading slurry, which typically costs £1/m3."

Simple ways to decrease slurry volumes are to divert clean water away from the store, using guttering, drains and so on. Reducing and re-using parlour washings, and storing dirty water away from the slurry store to spread on land throughout the year, can also make significant savings, both in water costs and storage capacity.

More expensive, but effective options include covering open yard areas, slurry stores and silage clamps, says Andy. "The wizard provides generic costs to these, or farmers can add their own values. They can then amend the data in the model to discover what effect each option will have on storage requirements and profitability."

The wizard comes with a comprehensive manual, Cost effective slurry strategies on dairy farms, which offers a wealth of practical advice on slurry management, complete with farmer case studies.

To order your free copy of the Slurry Wizard contact DairyCo on 02476 478695 or email

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