Making better use of existing soil phosphorus reserves could greatly reduce the risk of spring-sown crops running short of this essential nutrient during establishment.

Spring cereals, in particular, have a high demand for P in the first few weeks after germination. But they are often unable to secure enough to support optimum growth even where the nutrient appears to be plentiful.

Agrovista's technical manager, Mark Hemmant, explained: “Phosphorus is critical for cell biochemical functions and cell division, so is required in relatively large quantities during seed germination and establishment to underpin healthy root and shoot growth.

“New sowings on high calcium or high pH soils are especially vulnerable to shortage, as most of the phosphorus is bound up as insoluble calcium phosphate and is not available to the crop. This risks poor growth and tillering and puts plants on the back foot before they can get going.”

Applying bagged fertiliser to overcome this is expensive and inefficient, he argued. Depending on soil type and pH, as much as 90% of P applied in this form can be locked up quickly, often within days.

“It makes much more sense to make use of what’s already in the soil,” he said. “In these situations, I advise using Phosphorus Liberator, a soil-applied product that can free up significant amounts of P in a very short time.”

This is based on carboxylic acid technology and releases bound calcium phosphate, keeping it in solution, where it breaks down into its constituent parts. This ensures phosphate is available for root uptake during the first critical few weeks.

The product can be applied through a conventional sprayer pre-drilling or tank-mixed with a wide range of pre-emergence herbicides at rates tailored to soil P levels and crop need.

It is effective over a wide temperature range, is biodegradable and is not classified as hazardous to the environment, with the added benefit of reducing fertiliser bills and improving efficiency from applied phosphate fertilisers and manures.

Its potential in boosting spring crop performance was shown in a fully replicated trial on heavy calcareous soil at Agrovista’s flagship Project Lamport trial site, in Northamptonshire, last season.

A statistically significant 0.4t/ha yield increase was seen in plots where the product was applied pre-emergence, compared to the untreated controls, despite applying a commercial rate of bagged phosphate fertiliser to the whole trial.

The effect could also be seen in grain specific weight at harvest, which increased by 1.49kg/hl. “Both gains were impressive and statistically significant, despite there being no visual difference observed between plots,” said Mr Hemmett.

“We saw similar results in spring barley, and it seems likely we could see an increase in specific weight in spring oats. Meeting milling specification is critical with this crop, so that’s an area we will be looking at.”

Late-sown beans which came under extreme drought stress in the spring showed a positive response to it last year. Oxfordshire-based agronomist, Quentin Ham, conducted a split field trial on winter beans sown at the end of December.

Phosphorus Liberator was applied at 10 litres/ha with pre-emergence herbicide to an area of crop, the rest received pre-em only. Plant numbers on the treated area hit 22/sq m on 4 April, compared with 13 on the untreated area.

Foliar and root weights were 133% and 122% higher respectively on the treated part. “Visually we saw a big benefit in establishment and in plant weight,” he said.

The hot, dry and subsequent drought conditions for the rest of the season took its toll on the trial site's sandy soil. However, plants on the treated area formed more pods than the untreated before the main impacts were seen and thus performed to the national average.

“The field had a P index of 4.2, but we still got a good response, showing that even where there appears to be plenty of phosphorus it is important to make sure it is available to plants during the critical early phase,” added Mr Ham.

“I have used it commercially and run a lot of trials and have had a 100% strike rate, seeing massive plant responses. The additional root growth enhances a crop’s ability to capture nutrients, manage against root-related diseases and cope with drought conditions"

How to use it:

• Apply through conventional boom sprayer at usual water volumes;

• Widely tank-mixable with agrochemicals, including glyphosate and many pre-emergence herbicides;

• Apply pre-planting to early crop emergence;

• Apply at 5 litres/ha when used alongside phosphate fertilisers or organic manures;

• Apply at 10 litres/ha when applied alone.