Some producers are still waiting for ideal maize-sowing conditions, while others have already drilled. We offer some timely early-crop-management advice for all forage-maize growers.
TEXT WENDY SHORT
Maize drilled from mid-May onward is classified as late, so producers still waiting for ideal conditions may need to set the drill to a deeper levels – of about 7cm and no more than 9cm. That’s the advice from KWS’ Andrew Cook, who says that deeper sowing will allow the seed and seedlings to access soil moisture that could be lacking at this time of year. “Soil temperature must have exceeded 10 degrees C for five consecutive days before drilling, and the figure should be adjusted to 8 degrees C for light soils and 12 degrees C for heavy soils,” he adds.
“Efforts to achieve a friable, well-oxygenated seedbed will also pay off in terms of harvest results. And lack of soil moisture for late plantings can be mitigated to some extent through the use of a Cambridge roll, where appropriate.”
Typically, varieties in the higher FAO number, or maturity range, do not have quite the same degree of cold tolerance compared with ultra-early or early types, which have a lower FAO classification. “So it’s also worth checking the accuracy of drill settings before drilling because double-planting can cause problems later on. These can include weak root structure and the risk of two small ears instead of a single, large cob, as well as yield and maturity fluctuations.”
He adds that ‘buttress’ roots must be covered across at least 90% of the crop to enhance root anchorage. “A seeding depth that is too shallow may limit drought tolerance on light soils and possibly predispose the crop to lodging on highly fertile land.”
Looking to fertiliser inputs, high prices coupled with concerns about environmental pollution, have led to a review of application policies on many units. “It is vital to closely match fertiliser application to crop demand,” he says. “Late drilling offers the opportunity to cut DAP/ MAP phosphate fertiliser rates from 125kg/ha to between 65kg/ha and 70kg/ha, because nutrient mobilisation will increase as the soil warms up.
“Ammonium nitrate or prills can be used as a topdressing, but their use should not be extended beyond the four-leaf stage due to the risk of scorching.
Producers should wait until rain is forecast before application, to ensure the nutrients can access the root zone.”
Early maize: post-emergence management should focus on weed control
Producers who have already drilled maize crops will currently be facing post-emergence herbicide decisions. “Early-stage weed control must be prioritised, because young maize plants are extremely vulnerable to competition.”
Decisions on whether to apply a foliar feed will depend on a range of factors, including site location and soil type. “Some producers will have soils that are deficient in micro-nutrients such as zinc, manganese and boron. This situation needs to be remedied, as shortages can potentially compromise growth rates and plant health. Micro-nutrients can be applied as foliar sprays that are used when the plant growth point is under nutritional stress and during a period with a forecast of rising temperatures.”
Mr Cook adds that, as the season progresses, it can be useful to evaluate maize performance by monitoring what is going on under the soil. “It can help to predict harvest date with greater accuracy. One option is to use the KWS online heat units service, which is free to all producers.
“Simply enter the farm postcode and sowing date to find the average heat units for the location,” he explains. “The data is updated on a weekly basis, and the tool will also predict harvest date, based on the crop reaching a grain moisture content of 35%.
Pest damage: look out for European corn borer infestation
Producers should also keep a close watch for pests and diseases. European corn borer (ECB) moth was first identified in the UK in 2010 and incidence has been mainly confined to Devon and Dorset, although it has also been confirmed in maize crops in Kent. Its caterpillar stage causes physical damage, which increases the risk of fusarium ear rot and can result in lodging in later season.
“Good stubble hygiene is essential for ECB control,” says Mr Cook. “Continuous maize is high risk and the pest has other host crops, including oats, potatoes and beans.”
The adult moth is buff/brown in colour, with a wing span of about 33mm, and it will fly from field to field so infestation can spread rapidly. Eggs can build up in soils and these develop into off-white or red/purple larvae, which have striped and spotted bodies.
The critical period for controlling fungal disease in maize is between mid-July and mid-September. But this will depend on the weather, and early signs of disease can be tackled if signs are spotted in the early stages, according to Mr Cook.
“Maize is not particularly prone to disease, but eyespot can sometimes be seen from the eight-leaf stage. This can be controlled by a fungicide regime containing triazoles and/or strobilurins,” he says. “The same programme can be applied if the threshold for northern corn leaf blight is reached. Producers should take action if 30% or more plants are affected.”
The other fungal threat to maize comes from smut, with symptoms first appearing at the eight-to-ten leaf stage. “Damaged crops are the most vulnerable, and the spores can survive for up to a decade,” says Mr Cook. “The best ways to avoid disease are to instigate crop rotation and optimise soil structure.”
Find the KWS heat units service, and other useful free digital tools, at: www.kws-uk.com/mykws.