12 September 1997

DMtesting vital for maize

EARLY indications are for a bumper maize harvest as cutting gets under way in the east of the country this week, but further west changeable weather could make it difficult to achieve desired dry matters and delay cutting.

If it rains when the crop is almost at optimum dry matter, harvest will be delayed as growers wait for it to dry out, according to Maize Growers Association agronomist Simon Draper. "Crop DM could swing from one extreme to the other over a few days, so accurate dry matter testing will be essential."

Soil conditions could worsen if there is much more rain, so it will be best to harvest quickly, providing the crop is at least 30% DM, and ground conditions are good enough to prevent damage, adds Mr Draper.

"Everyone will want the contractors at the same time. Give them as much notice as possible. And when time is short, ensure crops on riskier soils are harvested first. Then you can allow the contractor to come back later."

Grainseeds John Hardy also urges producers to harvest as soon as possible. In some parts of the country, particularly the south west, soil is near saturation point and there is concern that a wet harvest will cause compaction and the following crop will suffer, he warns.

The window for harvesting within the suitable dry matter range is three to four weeks. But he advises harvesting as soon as dry matter reaches 27%, if ground conditions are good, because some plant roots are not holding well and crops may start leaning.

Nigel Jones of Huntseeds says the leaning is caused by fusarium, which dislodges the roots. "Maize crops inclined to lodge must be cut when ready, while crops that stay green are safe to leave for longer."

When cobs are fit to harvest, but the crop is still green, there may be some effluent, says Mr Hardy. But the grain will soon start to soak up the excess moisture within the clamp. Cutting the crop higher can also increase the dry matter in the clamp, and reduce the risk of effluent, he adds.

Devon milk producer Charles Moore says maize fields must not be left as stubble over winter. Ploughing, subsoiling or sowing a cover crop will be essential to prevent run-off of soil and nutrients, which causes pollution, he warns.

He advises subsoiling across the slope of a field to avoid erosion. "When it is not dry enough to subsoil use a spring tine cultivator or a few passes with the plough, at intervals of, say, 50 yards across the slope." The gap between plough passes should depend on the nature of soil, slope of the land and risk of erosion, he adds. These cultivations should be carried out as soon as possible after harvest.

Mud on roads while maize harvesting should also be prevented, says Mr Moore. Mud must be cleaned up for traffic safety and to prevent contaminating watercourses.

&#8226 Changeable weather is making it difficult to predict maize dry matters and hence harvest dates on FW monitored sites (see table). The Norfolk site has seen recorded DM vary by 10%, falling by 6% last week before a rise of 9.3% this week, and bringing harvest dates forward by 10 days. Overall maturity has increased by between 2 and 5% across the seven sites. &#42


Forage maize dry matter data from seven farms

Site locationDM%

Sep 4

Crediton, Devon22.4

Attleborough, Norfolk 31.2

Gelli Aur, Dyfed21.9

Winchester, Hampshire24.1

Ticknall, Derbyshire25.3

Castle Howard, Yorkshire19.0

Dumfries, Scotland17.2