AGRONOMY UNDER AGENDA 2000 SPOTLIGHT
AGRONOMY UNDER AGENDA 2000 SPOTLIGHT
GROWERS have three years to learn to cope with earlier drilling and should start to gain experience this autumn so they are better able to handle the crop when much more is grown, says Dalgetys Mike Jeffes.
"Although there could be a lot more wheat grown in 2002, the area drilled next season is likely to increase significantly. If 150,000ha of this seasons huge linseed crop is switched into wheat and a further 50,000ha is trimmed from the rape crop, there will be 10% more wheat to go in this autumn," says Mr Jeffes.
"It would be a big mistake to carry on as usual as valuable lessons can be learned before the area peaks and the pressure is on.
"With more wheat on fewer, larger farms with less labour, drilling will be a long drawn out job. After last autumns experience, no heavy land wheat grower will want to mess about drilling in November. So the job will have to start sooner. But for ultra-early drilling, varieties must be chosen carefully."
Normally early sown wheat is taller, produces more bulk and is more likely to lodge than later drillings. So stiff straw is vital.
Temperatures in the first three weeks of September are usually higher than at the end of the month so disease pressures, particularly from mildew, Septoria tritici and yellow rust, are greater.
Skilled agronomists can keep crops standing and disease-free – but at a cost. It is far cheaper to exploit the genetic disease resistance of some varieties, Mr Jeffes believes.
Early September sowings demand slow developers with high vernalisation need, he advises. If a fast moving type with hair-trigger vernalisation goes in early it can reach stem extension (GS30/31) in late autumn, risking apex abortion and crop loss from frost.
"So varieties need to be stiff strawed, disease resistant, and slow developers. With an increased eyespot threat and because resistance is "diluted" by early sowing, varieties with top-end ratings must be also used.
Mr Jeffes suggests Consort in preference to Riband as it is slower to develop, stiffer, and has better disease resistance. Buchan is a better bet than Reaper which is tall, weak and relatively fast. Slower Madrigal has the edge for early drilling over Soissons as it needs plenty of cold before it develops properly.
"No matter which variety is chosen it is absolutely no use drilling 300-350 seeds/sq m in early September as this will result in a flat crop.
"Leaf and tiller production in wheat depends almost wholly on accumulated temperatures. If high seed rates are used early crops are likely to be massively over-tillered and more prone to disease and lodging, so seed rates must be cut."
If early September seed-beds are moist Mr Jeffes aims to drill 170-180 seeds/sq m. For a crop sown in the second week of September this can be stepped up to 210, with 240 mid-month, and 270-300/sq m by the traditional start date.
"Drilling low seed rates means there is less room for error. Losses can soon reduce plant populations below the optimum for yield. So top quality high vigour seed must be used." And with increased disease pressure a Baytan (fuberidazole + triadimenol) seed treatment is essential, he says.
"But 180 seeds/sq m is only about 40% of more traditional rates. So the cost/ha of the fungicide is probably less than a single purpose seed treatment used later in the season when more seed is drilled."
With more second and third wheats grown, take-all could be more severe. Agronomic measures can reduce the fungal threat. One is to give priority to less vulnerable crops.
As take-all is unlikely to be particularly threatening to first wheats they should go in first, with second wheats following and third wheats left until a more normal drilling time, advises Mr Jeffes. Doubling the amount of early spring nitrogen, at the expense of later applications, will stimulate root growth allowing the crop to shrug off the fungus and make better use of subsequent dressings.
Two new seed treatments tested at Dalgetys Throws Farm, Essex offer the prospect of chemical take-all control. One from Monsanto has been used since the early 1990s. Targeted just at take-all, MON 65500 has boosted second wheat yield by 6-7%.
AgrEvos fluquinconazole has broader spectrum action. It is as effective as the Monsanto product in controlling the fungus but has the bonus of disinfecting seed, and offers longer lasting systemic disease control than Baytan. *