Research by leading agronomy firm Hutchinsons has shed new light on the benefits that a phosphite biostimulant application can have on wheat establishment and final yield.

Replicated trials conducted on two North Yorkshire farms last season by Hutchinsons agronomist Sam Hugill found that a single late-October application of a foliar phosphite product significantly improved tillering and strengthened the resilience of those crops to overwinter damage.

Monthly tiller counts revealed the late September-sown plots of Group 4 Revelation, both on heavy clay sites saw a 17% increase in tillering last December and by early February this benefit had doubled to a 34%, which carried through to a 6% yield improvement at harvest.

The foliar phosphite product, containing nitrogen, phosphoric acid, potash (6-23-4) and additional zinc, was applied at the recommended 1 litre/ha around a month after drilling at growth stage 13. Its performance was compared against an untreated plot and two other treatments of an epoxiconazole + fenpropimorph-based fungicide (0.75 litres/ha) and a chlormequat growth regulator (0.5 litres/ha).

“Applications of the fungicide and plant growth regulator had no impact on tiller numbers or winter survival, but we saw clear physiological benefits from the foliar phosphite in building root mass,” says Mr Hugill. “This makes the plant better at scavenging nutrients and putting on tillers.”

Both fields are prone to poor establishment caused by winter waterlogging, so increasing root mass and the number/ resilience of tillers can help overcome stress events or root disease and make a real difference to yield potential coming into the spring, he says.

“Tiller survival influences final ear numbers which has a major influence on yield. We need to jump at the chance to be able to boost our growers’ yield, which ultimately results in an uplift of the gross margin.”

Mr Hugill says the weather was relatively kind last winter which may have reduced the yield benefit recorded this harvest. A bigger difference may well be possible after a harsher winter, especially on heavy soils prone to waterlogging, he suggests. He is repeating the trials again this season in a different variety, KWS Barrel, and will further examine the impact of different dose rates as well as other foliar products.

“A lot of growers are interested in the product, so we’ve got a really good opportunity to further confirm its performance across a range of situations and soil types.”

Phosphites v phosphate

Phosphorus is an essential element in all living cells, but there are important differences between the nutritional effect of conventional phosphate fertilisers derived from phosphoric acid and the physiological impact of phosphite products, made from phosphorous acid.

Phosphite is much more soluble than phosphate and although plants cannot use it as a direct nutrient source, they can take it up through the leaf vacuole where it is then used to boost root/ root hair development and stimulate nutrient uptake from the soil, Hutchinsons technical manager Dick Neale explains.

This differs from phosphate which is too large and insoluble to break down quickly meaning that it is more effectively taken up from the soil by roots. Foliar phosphate is more at risk of sitting on the leaf surface where it is weathered and a proportion may be lost to the environment. Phosphate and phosphite cannot be used as substitutes, he says.