22 March 1996

Trials show yield boost with routine PGRspray

By Robert Harris

GROWTH regulators should be applied routinely to poorly rooted winter cereals to boost yield even when lodging is not expected, recent work suggests.

Twice the yield gain normally achieved with a growth regulator programme was obtained on Cadenza wheat in five Crop Technology AgriFocus trials at Wilton last year, says Masstock Arables technical manager Clare Bend.

"Every time we put growth regulator on last year we got a positive yield response although there was no lodging. And the mean response was 8%, approximately double that seen in previous years using a reasonably reliable product like Meteor."

It is unclear where the extra yield came from, she admits. "We analysed crops for ear number, grains per ear and thousand grain weight but we couldnt find any consistency."

But part of the reason appears to be better rooting. The wet winter restricted root development, and the dry spring left crops at risk of drought. Growth regulators applied before or at the end of tillering (GS29) encourage better root development and tended to produce the highest yields, she explains.

The standard treatment, Meteor (chlormequat + choline chloride + imazaquin) applied at GS29 at 2litres/ha (1.4pt/acre) followed by Terpal (2-chloroethylphosphonic acid + mepiquat chloride) at flag leaf emerged (GS39) at 1litre/ha (0.7pt/acre) boosted yield by 10% compared with untreated plots.

Others treated with a single application of newcomer Moddus (trinexapac-ethyl) at 0.4 litres/ha (0.28pt/acre) at ear at 1cm to third node detectable (GS30-33) averaged about 9% more yield.

"Weve had the product in trial for three years. It has performed very well, though no better than the current standard. But we have not been able to evaluate it in a lodging situation," says Mrs Bend.

In Halcyon winter barley, crop stress caused more variable and lower responses. Treated plots averaged 5% more yield. An early application of 0.3litre/ha (0.2pt/acre) of Moddus at GS30 followed by Terpal at flag leaf boosted yield by 6%, twice that of the nearest competitor mix.

It also gave the shortest canopy, a good indicator of lodging resistance in barley, says Mrs Bend.

Early growth regulator sprays boosted root growth and yield in AgriFocus trials last season, says Masstock Arables Clare Bend.