Spring applications of P and K could prove beneficial to crops

GROWERS are being advised it is not too late to apply phosphorous and potash treatments to crops, despite many missing the more traditional autumn applications.

According to a survey of more than 1,000 farmers, carried out for Yara before Christmas, more than half of respondents had yet to buy P and K for the 2012 harvest crop, indicating a slow pattern to purchasing for this season.

The company’s agronomic co-ordinator Ian Matts says the volatile nature of the fertiliser market, rather than agronomic factors are the likely reason.

“Volatility and cost are important and I believe people will be wanting to put on similar amounts of P and K as last year, but they are probably holding back in order to look for the best deal,” he says.

But while some growers may feel they have already missed the traditional P and K application window for this season, Mr Matts says a spring application could prove more beneficial to the crop.

“Treatments applied in the autumn can lead to nutrients being ‘locked up’ and therefore not available to the crop.

“As long as soils are above an index 0 and capable of matching the crop’s requirements during establishment, spring applications of phosphate and potash can be more efficient.”

Yara trials have shown a 50 per cent increase in uptake efficiency of P in the spring compared with applications in the autumn, he says.

Mr Matts also advises growers against taking a P and K ‘holiday’, particularly if there have been treatments missed in recent seasons.

Deficiencies

“Taking a break from P and K could lead to soil deficiencies, causing serious yield penalties in the future. It’s much easier to maintain levels of P and K than having to try and build them up again if the soil levels become depleted.”

With target indices varying according to soil type, but generally 2 for P and 2- for K, Countrywide Farmers agronomist Simon Trenary, advising on land in Wiltshire, Somerset and Oxfordshire, agrees farmers are holding back on spending on P and K a little longer than usual.

“People are certainly hanging on to their cash for longer, but the key thing is that growers justify the need of P and K by regular sampling of fields,” he says.

Using current prices, and the example of a winter wheat crop yielding 8.6t/ha (3.5t/acre), the cost of P and K replacement for grain is £92/ha and straw £28/ha, resulting in a £120/ha total cost when both are taken into account.

Where yields are higher than this, P and K off-take could be higher too, and growers should bear this in mind when putting together crop nutrition plans, says Mr Trenary.

However, providing the soil indices are good, it doesn’t matter if maintenance P and K applications are fitted in with the rest of the farm’s workload, he says.

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