Poultry manure management rules being introduced by processor Avara will see Welsh broiler suppliers complying with robust new standards to prevent pollution of the River Wye and other watercourses.

Over-applying poultry manure to fields can have serious consequences for the environment in soil and water while manure that isn’t properly managed emits harmful methane, carbon dioxide and ammonia.

Managing these nutrients for maximum benefit and minimal environmental impact requires planning, says Ceredigion-based soil and grassland specialist Chris Duller.

Mr Duller says there are a number of steps poultry producers can take to protect their soils and the environment, including matching the application rate to the nutrient value.

The phosphate (P) content of typical poultry manure at 40% dry matter is four times higher than the levels in farmyard manure from cattle and nitrogen (N) is three times higher.

Recommended application rates are therefore considerably lower.

While cattle manure is mostly applied at 5t/acre, Mr Duller says poultry manure applications should be no more than 1t/acre on grazing land and 2t-3t/acre for silage ground.

The ‘gold standard’ is to apply poultry litter to arable land during cultivation, when it can be incorporated into seed beds which are often nutrient hungry.

“In an all-grass farm is chicken muck the best nutrient we can use? The answer is ‘no’ because losses occur when it sits on top of grass,’’ Mr Duller explains.

“Also because phosphate content is very similar to potash the majority of poultry manure application tends to oversupply phosphate and undersupply potash to grassland.’’

Always sample soils for nutrient status before applying poultry manure as indexes could already be high.

If soil pH level is low the N and P supplied by poultry manure won’t be used efficiently, reducing plant uptake and increasing risks of wastage.

Mr Duller says some of the soils he has sampled on poultry farms are at index 6 for P, with the highest mostly on long-term grassland where the levels accumulate at the surface.

Once soils reach P index 3 there is only a crop requirement for 20kg/ha/year of phosphate in a silage system, so 7.5t/ha (3t/acre) of poultry manure will oversupply by 70kgP/ha, he points out.

“Do that for 3 years and your soils will jump up an index.

“It can take 50 years to get the index back from 6 to 2, a farm should definitely not be applying chicken muck on that land.’’

When indexes are high, get advice from a professional on how to manage those soils going forward.

If soils have a low index, values will quickly increase when poultry manure is applied so regular sampling is needed – Mr Duller recommends every three or four years.

If compound fertiliser is applied to land where poultry manure is used, he advises using a N and potash (K) product – avoid anything with P in it.

A common mistake is to store poultry litter with other manures but in that situation the nutrient status of the manure will be an unknown.

“It is very difficult to do the sums on rates and to work out what other fertilisers are needed when manures are mixed so always have distinct heaps for different types,’’ says Mr Duller.

Mixing also limits opportunities for spreading other manures in a Nitrate Vulnerable Zone (NVZ), he adds.

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“Poultry manure is classed as a high readily available nitrogen (RAN) manure so in Wales for instance, in 2024 farmers will be prevented from spreading those manures between 15 October and 15 January but there are different rules for cattle manure.

“If cattle manure is mixed with poultry manure it can’t be applied in that closed period either.’’

A 32,000-bird system will produce around 14t of manure a week so at application rates of 1 or 2t/acre between 350 and 450 acres of land is required for spreading the annual 700t output.

Many farms won’t have that acreage so Mr Duller advises setting up manure export agreements with arable systems where poultry manure is an asset for crop production and cost competitive with inorganic fertiliser, even accounting for transport costs if done on a local basis.