High rainfall adds to maize N leaching

7 May 1999

Tough ammonia laws likely

By Jessica Buss

AMMONIA emissions from livestock manure must be reduced to comply with an EU directive, and new legislation for producers is likely within the next few years, warn researchers.

Of the 350,000t of ammonia gas released into the air each year, 80% is said to come from farming, with huge amounts coming from housed livestock, according to ADAS figures.

At last weeks Muck 99, near Driffield, East Yorks, researchers involved in MAFF-funded projects aimed at reducing emissions economically believed strong environmental pressures in the EU would soon force new legislation. Big pig and poultry farms are likely to be affected first by the EU Integrated Pollution Prevention and Control Directive.

New units of over 40,000 birds, 2000 production pigs or 750 sows would be affected by the directive later this year, said ADASs Brian Chambers. These rules were expected to apply to existing units in 2007, but that date may be brought forward, he added.

Despite legislation coming into force first for pig and poultry farms, half the ammonia emissions came from cattle farms, according to Brian Pain of the Institute of Grassland and Environmental Research.

"The amounts are significant, with 25kg of nitrogen a dairy cow – equivalent to 70kg of nitrogen fertiliser – lost as ammonia gas each year for cows on slurry-based systems. This is a major source of nitrogen loss, so there are economic benefits in trying to conserve it."

Producers would need to use the best available technology to reduce ammonia emissions, providing the cost was economic, said Dr Chambers. He believed pig producers would need to begin using band slurry spreaders to lower ammonia emissions. But they also offered the best use of slurry, said Dr Chambers, while Dr Pain warned that using a plate spreader to apply slurry produces high ammonia losses.

Other options for spreading slurry closer to the ground, or injecting it are better. Using a trailing shoe spreader in grass of 10cm-12.5cm (4in-5in) reduced ammonia emissions by up to 75% in ADAS/IGER studies. Practical farm trials on low trajectory spreading will begin this year.

Dr Pain also believed legislation requiring slurry stores to be covered would be introduced. "All Dutch farmers cover their slurry stores. The most popular way is with plastic sheeting fixed like a tent."

This and other options for covering tanks and lagoons are being researched at Silsoe (see p40). Adrian Williams of the Silsoe Research Institute added that covering slurry stores, even though not the biggest source of ammonia losses, could save buying nitrogen fertiliser worth £3.2m a year. But cheaper methods of covering slurry stores must be found.

Housing type may also influence ammonia losses. John Williams of ADAS Boxworth said a MAFF funded study showed ammonia losses were 16-18kg of ammonia for every 500kg liveweight of pigs housed in both straw and slurry based systems.

"But with straw systems most losses – 12-16kg – occur in buildings, where they are difficult to control. In slurry-based systems only 8kg is lost in buildings and 10kg is lost during spreading," said Mr Williams. &#42


&#8226 Legislation likely.

&#8226 Valuable nutrients lost.

&#8226 Cover slurry stores.

Ammonia losses

Housing 39%

Land spreading 30%

Storage 8%

Outdoors 13%

Fertiliser 10%

Source: IGER.

Seven ryegrass varieties join list

SEVEN new ryegrass varieties have made it on to this years NIAB recommended list while six older varieties have been removed.

Perennial varieties take four of the seven new additions to the list – AberDart, Corbet and the tetraploids Calibra and Fornax.

But Grassland Research and Advisory Service technical adviser Robin Turner says that is more to do with results of testing programmes that began 10-15 years ago than popular demand.

Producers are after two grass types: One for silage making and one for long-term grazing, he says. "These new intermediate varieties will yield well for first and second cuts and provide a good sward for aftermath grazing."

Other new varieties include an early variety, AberStorm, a late variety Navan and one Italian variety, Fabio a tetraploid.

But Dr Turner urges producers to pay more attention to grass varieties to help improve grassland management. "Two generations ago producers knew about grass varieties. Now they know about mixes but not varieties.

"This is reflected in less than adequate grassland management, meaning they do not make best use of grass," he says. &#42

Dairy research network

A NEW national research network, Ethos, has been launched by feed manufacturer BOCM Pauls.

Reacting to its dairy customers varied and changing requirements, BOCM Pauls has widened its research objectives to cover more aspects of dairy production.

The firms national cattle adviser Bruce Woodacre says producers are considering different ways of making profits, including organic milk production, high genetic merit cows and cheesemaking, and research must reflect this. "With Ethos we aim to put research into practice for dairy producers whose production systems vary from grazed grass to elite cows."

BOCM Pauls has also forged formal links with Dairy Research and Consultancy.

Other Ethos projects include work at ADAS Bridgets, Hants, on its elite herd and research on Jersey cows at Brackenhurst College, Notts. Other projects at Harper Adams College, Shropshire, and Duchy College, Cornwall, will focus on commercial farm situations. &#42

High rainfall adds to maize N leaching

HIGH rainfall means more nitrogen than usual may have been leached from maize fields this winter and some crops may require top dressing once emerged.

MGA agnonomist Simon Draper says that where muck has been applied, a higher level of mineralisation due to warmer temperatures will compensate for extra leaching. But where muck has not been spread, more nitrogen may be needed.

"Growers who have already planted maize crops should wait and see what crops look like and decide whether to apply more nitrogen once plants have emerged. When crops have not yet been drilled, carefully consider the nitrogen required," says Mr Draper.

Nitrogen requirements will vary from field to field, but often the same amount is applied to each field. "Even on a single farm rates can vary from 0-150 units/acre, according to results from MGAs Nitrogen Predictor service."

Mr Draper says last years cropping, the fields previous 10 years history and farmyard manure applications can affect nitrogen supply. "When FYM is applied after March it is of little use to that years crop." But a build-up of manure spread each year onto fields which continually grow maize will add to the nitrogen available. &#42

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