Arable growers are being advised to test soil mineral levels for available phosphorus post-harvest to prevent deficiencies that could impact crop growth this winter.

According to David Harrod, arable business manager at Timac Agro UK, a P deficiency is often under-diagnosed, with crops usually displaying no obvious symptoms other than stunted growth.

“By the time crops show symptoms of phosphorus deficiency, it’s too late to reverse,” he says. “The long-term implications include underdeveloped root systems, lack of strength in the plant stem and stalks, and a lack of uniformity; all of which impact yield and quality at harvest. But this can be easily prevented ahead of autumn drilling.”

Preventing problems

David explains that to prevent these issues, all fields, post-harvest, should be soil tested to understand the mineral composition and wider soil health status.

“The ability for crops to uptake P can be impacted by other mineral deficiencies, so having a full outlook of macro and micronutrients is key.”

While undertaking testing, David notes that of equal importance is measuring organic matter levels, as this, along with the P and K status will give growers an idea of your soil fertility.

“While taking samples for a soil test, grab a spade and look at the wider soil structure and ask yourself, is there a high worm population (more than 10 per spade full)? Is the soil consolidated or aerated? What does the structure look like? This will help identify how ‘alive’ your soil is.”

Rectifying low levels

If soil test results indicate low levels of P, David recommends using a phosphorus fertiliser, such as Top-Phos.

“By applying P early with an enhanced fertiliser, we’re ensuring the crop receives nutrients early in the season to optimise plant and root growth,” he explains.

“Top-Phos is a unique chemical form of phosphorus. Unlike standard forms of P fertilisers, the chemical make-up of Top-Phos protects it from being locked up by the soil. This maximises the availability of P to the crop and increases root mass, improving P efficiency.”

Trial results

Trial results using Top-Phos compared with a standard P fertiliser resulted in root volumes doubling, alongside a 25% uptake in available P in the soil, resulting in increased yields

“We’ve also seen industry trials which saw up to double the amount of microbial life per kilo of soil following applications of Top-Phos,” he adds.

“With N prices not looking to come down in the distant future, and concerns over input availability, planning now to ensure you’re setting crops up well, will pay dividends on the weigh bridge next harvest.”