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30 Jun 2021

Focusing attention on phosphorus status

As featured in Arable Farming Magazine

Focusing attention on phosphorus status

by Arable Farming

According to the British Fertiliser Survey, an average muck heap could contain around £1,000 worth of P.

Management of phosphorus supply to crops and grass will be the focus of the coming years FACTS Annual Online Assessment, which aims to enhance efficiency and reduce potential pollution on UK farms.

The assessment, which will run from June 2021 to May 2022, is tailored to grassland and arable farms.

To maintain their status as FACTS Qualified Advisers (FQA) the almost 4,000 members on the BASIS Professional Register will need to undertake the online assessment during this period.

Training courses may be offered by BASIS-approved trainers, but all the necessary information will be issued in the quarterly bulletins sent to FQAs.

Separate online assessments have been launched for those who advise on turf or horticultural crops.

Phosphorus has been chosen for a range of reasons, according to Ian Richards, who operates the FACTS Advisory Service.

Environmentally, there are concerns over the role of P in effects such as eutrophication in surface waters and the need to avoid losses through run-off.

However, there is also a need to get P indices in soils nearer to their target of 2 in most soils, or 3 where there is a significant proportion of vegetables in the rotation.

Mr Richards says: We now have soil testing data going back over 25 years and I would have expected to see soil indices for P converging on the target.

That is raising those with a low P status and reducing levels in soils with high status.

Indices In fact, only 9-10% of British soils are at the target indices for both phosphorus and potassium.

Farmers and advisers need to be encouraged to target P use with the same precision as they apply to nitrogen.

With most soils being regularly sampled, adjusting P levels by following the RB209 guidance should be achievable by paying attention to soil analysis results.

Where soils have high levels, money is being wasted by applying more either as manufactured fertiliser or as organic matter or manures, adds Mr Richards.

Manure use is a particular issue and results from the British Fertiliser Survey suggest insufficient attention is being paid to the P which may be provided.

An average muck heap could have around £1,000 worth of P stored in it.

Not appreciating this value will result in money being wasted.

How P may leave fields will also be addressed in the coming years assessment.

It is becoming clear that many factors influence how P can be lost.

Key among these is soil type, the slope of a field, prevailing weather conditions, especially rainfall, and cultivation methods, as well as proximity to water.

By understanding these local factors, good management can significantly reduce losses from fields.

Mr Richards is encouraged to see an increasing awareness of soil as a resource for agriculture and believes increased attention to P status will become ever more important.

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