Farmers could be losing as much as £80/ha through incorrect timing and application of manure and slurry to their grassland.

At a farm demonstration day in Somerset last week, the England Catchment Sensitive Farming Delivery Initiative - a collaborative project delivered by Natural England, the Environment Agency and Defra - revealed how critical timing and application techniques were to nutrient losses and availability.

Farmers applying a typical dairy slurry with a 6% nitrogen content in the autumn, to the surface of medium to heavy soils, would only get a plant uptake of 15%, said Promar consultant Tim Harper.

Conversely, spreading the same slurry in the spring would result in a 35% take-up of nitrogen if surface-spread; 45% if the slurry was incorporated within six hours, or a 50% uptake if it was deep injected.

"Fertiliser prices have increased drastically - and that isn't something which is going to go away," said Mr Harper. "Farmers need to make the most of their slurry and manure - and the key factors which affect their efficacy are the type of manure, the timing of application and the technique used."

These issues also affected pollution levels in the river catchment area, said CSF officer Louise Webb. "The Tone catchment is very close to failing on levels of nitrate and phosphate - and that's why Nitrate Vulnerable Zones are being extended."

Farmers attending the free CSF open day at Smokey Farm, Taunton, enjoyed demonstrations of muck spreaders and splash plate, injector and trailing shoe slurry spreaders, allowing them to discuss the pros and cons of each method.

At current fertiliser prices, one dairy cow would produce slurry worth £50 over a six-month period, said Mr Harper. But applying that slurry at the wrong time and using the wrong method could slash that value to £32 or less.

Typically, applying slurry in the autumn resulted in poor plant uptake and leaching of nutrients, while spreading it using high-pressure, high-trajectile techniques caused massive nitrogen losses to the air.

Proposed changes to the Nitrate Vulnerable Zone areas and rules meant it was possible that such application methods would be banned, said Mr Harper. And there would also be significant restrictions on when and how farmers in NVZs could apply slurry to their fields.

These included a winter closed period of between 12 and 16 weeks, during which no slurry could be spread, and a requirement for 22 weeks of slurry storage - a massive hike on the current average of 10 weeks. "Assuming a write off of 10 years that investment would add 1.3p/litre/year to the average dairy farmers' costs."

To minimise storage requirements, farmers should try to reduce the amount of slurry produced, by preventing rainwater from entering the slurry system and maximising the amount of solid farmyard manure produced, said Mr Harper.

Anyone wanted to learn more about cost effective slurry and dirty water storage options can register for the CSF's next free workshop, which will be held on Mar 11 at Pyrland Farm, Taunton, from 10:30 - 3pm. For more information or to book your place call 0845 602 3864.

An open day covering both storage and use of slurry and manure will be held on Mar 6 at Sunnyfield, Honiton from 10.30 onwards. For more information or to book your place, call Tim Turner on 01823 285548.