Autumn micronutrient sprays help to raise wheat yields

A late-October foliar application of a phosphorous-based biostimulant improves tillering in wheat crops and lifts yields, new trials suggest.

Phosphite is a form of fertiliser that acts as a biostimulant, which gets crops off to a good start by encouraging early root development. Plants are then better able to access water and nutrients.

See also: 9 top tips for better cereals establishment

To see whether applying phosphite translates into higher yields, Hutchinsons agronomist Sam Hugill conducted trials on two North Yorkshire farms last season. 

Less overwinter damage

He found 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. By early February, this benefit had doubled, which carried through to a 6% yield improvement at harvest.

The foliar phosphite product, containing nitrogen, phosphoric acid, potash (6:23:4 NPK) and additional zinc, was applied at the recommended 1 litre/ha rate about a month after drilling at growth stage 13. 

Its performance was compared with 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 effect 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.”

Resilient roots

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.”

Mr Hugill says the weather was relatively kind last winter, which may have reduced the yield benefit recorded this harvest.

He believes a bigger difference may well be possible after a harsher winter, especially on heavy soils prone to waterlogging.

The trials are being repeated this season with the variety Barrel.

Phosphite v phosphate

Phosphorus is an essential element in all living cells and there are important nutritional differences between the two forms, leading to different physiological effect on plants.

Conventional phosphate fertilisers are derived from phosphoric acid, while phosphite products are made from phosphorous acid.

Consequently, 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, Hutchinsons technical manager Dick Neale explains. It is then used to boost root development and stimulate nutrient uptake from the soil.

This differs from phosphate, which is too large and insoluble to break down quickly. This means it is more effectively taken up from the soil through the 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 interchangeably, he says.