27 February 1999

ANCHOR STARTSAT THE ROOT

Lodging in cereals cost farming £120m last year despite growers spending more than ever on plant growth regulators. Lucy Stephenson finds out why.

MANAGE a crop properly and the result should be virtually no lodging at all, say the experts.

"Lodging is not an act of God, its to do with the way the crop is grown," says John Spink, a senior research consultant with ADAS. "Theres a tendency to miss the importance of sowing practice, lodging mechanisms, and poor identification of crops prone to lodging in the spring."

When a growth regulator-treated crop lodges its tempting to think the money spent on treatment has been wasted. Not so, according to Eric Gussin, of Cyanamid. Even where treated crops eventually flatten, delayed lodging gives a yield benefit of as much as £110/ha, and improves quality, he says.

Dr David Ellerton, technical director for ProCam Group, agrees advisers need to explain the rationale behind growth promoter recommendations at the start of the season, especially with high standing-power varieties.

Growth promoters reduce stem height, but agronomic factors influence crop lodging heavily. The HGCA-funded work by ADAS and Nottingham University shows stem lodging is affected by shoot leverage and stem strength, while root lodging is affected by whole plant leverage and anchorage strength. Leverage depends on the springiness of the stem, the number of shoots per plant, the height of the stem, and the weight of the ear.

Stem strength is affected by its radius, wall width, and material strength. Good disease control maintains the material strength of the stem.

"Theres not enough recognition of root lodging, but in my experience its the most common form," says Mr Spink. Anchorage strength is affected by the root plate spread, root depth, and the soil type and structure. The root plate spread – the top 1-2 inches where the roots are thickened and more lignified – is influenced by seed rate and variety. Anchorage is lower in friable or sandy soils and following rain. In summer, 5-10mm of rain is enough to weaken the top of the soil to the point that root lodging could be a problem.

In a cost squeeze, seed should be cut before the growth promoter programme, says Mr Spink, because crop density has a major effect on anchorage. "You see no yield loss for September-drilled crops until youre down to 100 seeds/sq m," he says. High seed rates cause a dramatic reduction in anchorage strength because the spread of the structural roots is restricted.

Pete Berry, of Nottingham University, who worked on lodging prediction in the HGCA project, says crop assessments made in the spring can identify lodging-prone crops. "Large canopies, those that are lush, or early application of N gives weak stems, and high plant populations produce poor anchorage."

He is warning that early sown crops this year tend to be both well established and lush.

Growth promoter applications will be needed for these crops to reduce crop height and encourage root development. Dr Ellerton suggests 2.5 litres/ha Meteor (imazaquin and chlormequat chloride) at growth stage 30 followed by 2/3 rate Satellite (imazaquin, chlormequat and 2-chloroethylphosphonic acid) at GS37. "If application is delayed to GS31, a possible approach would be to mix a half dose of Meteor with a low dose of Moddus (trinexapac-ethyl), about 0.15 litres/ha. Moddus can be an incredibly dramatic, very fast-acting product, but Meteor will spread the duration of its activity," he says.

Many of this years late crops now have inadequate tillers, which could affect yield. Growth promoters will encourage root development and tiller survival. Dr Ellerton recommends 1.75 litre/ha Meteor at GS24-29 then 0.75 litre/ha at GS30. Lodging risk should be reviewed at GS35 -37, but try to get in earlier, he says, because at GS37 the crop may be under drought stress and other farming operations will compete for time.

Dr Ellerton emphasises that NIAB ratings for standing power dont necessarily fully reflect lodging resistance. Equinox, with a 9 rating for standing power and shortness of straw, has poor crown root strength which might be countered by 1.5 litres/ha Meteor applied at GS25-29 to increase root strength and root angle.

Winter barley varieties such as Halcyon must be kept standing, but with low crown root mass its rated 4 for standing power, and 5 for shortness of straw. Dr Ellerton recommends 2.5 litres/ha of 5C Cycocel, or 0.2 litres/ha Moddus plus 1.25 litres/ha Cycocel at GS30 to boost root mass, followed by 2 litres/ha Satellite or 1 litre/ha Terpal (2-chloroethylphosphonic acid and mepiquat chloride) at GS37 to reduce height. He stresses the need to keep plans flexible, and to keep the lodging situation under review.

&#8226 A free copy of Cyanamids Plant Growth Regulator Handbook, a guide to planning against cereal lodging, is available to the first 1,000 Crops readers on request. It explains the theory and practice of growth promoter use, and normally costs £10.50. Write to: Cyanamid Agriculture Ltd, FREEPOST, Response Centre, West Farm House, Cams Hall Estate, Fareham, Hampshire, PO16 8YU.