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Drilling maize by soil temperature rather than calendar date is increasingly important in light of increasingly variable weather conditions during spring. With potential yield... Unpredictable weather changes emphasis for maize this spring

Drilling maize by soil temperature rather than calendar date is increasingly important in light of increasingly variable weather conditions during spring.

With potential yield loss from uneven emergence as high as 40% and poor seedbed conditions at drilling being a further challenge, growers need to take extra care with establishment, explains Neil Groom of forage maize specialists Grainseed.

“Drilling at the right time means more seeds are stimulated to germinate simultaneously,” he says.

“While this is usually from late April to mid May, of far greater importance is the availability of moisture and warmth in the seedbed.”

Soil temperatures must reach 10-12ºC taken at 9am for at least four days across the entire field due to be drilled, says Mr Groom.

Only once this threshold has been met is it safe to make a start.

“While soil temperatures remain low, producers should use the time to work the soil properly and ensure they are making as much use farm-yard manure and slurry as possible.”

Slurry and manure can be applied right up until drilling – but it is best to incorporate them in the top 10cms of the soil using heavy discs or a tined cultivator rather than deep ploughing, suggests Mr Groom.

“That way the roots can easily access the available nutrients as they start to grow. Manures should also always be incorporated into the soil within 24 hours of application to minimise losses.”

Test soils and manures

Knowing what nutrients your organic manure contains is essential in building an accurate fertiliser plan and ensuring they are all used to full advantage and in an environmentally responsible way.

“A good way to do it at this time of year is to collect samples directly from the spreader by putting some trays out under it, so you’re actually testing the material you are putting on the land,” says Mr Groom.

Soils should be tested too – with a particular focus on acidity, as well as nitrogen, phosphate and potassium content. Available soil nutrients should be factored into any application programme.

“With good nutrition and warm soils crops will grow away quickly but if the weather or ground conditions force later drilling, then moving maturity group up a notch to an earlier maturing variety than normally considered might be worthwhile.

“There’s very little yield penalty these days if you choose wisely and the reduced number of heat units required to finish properly will ensure you maintain feed quality and energy content at harvest.

“A group 10 variety like will produce a yield similar to a group 8 on most soil types and give a greater degree of resilience especially in a reduced growing window.”

MGA agronomist Jon Myhill says good seed-to-soil contact is essential but seedbed requirements  change depending on when the maize is sown, the soil type it is drilled into and the weather at the time of drilling.

“Many growers actually create a finer seedbed than is really needed. A rough seedbed may be best early on, say from mid-April, in a colder season as looser, rougher soil will warm up more quickly when temperatures do start to rise.”

Moisture retention

Later in the season, however, when temperatures have increased a bit, a finer tilth will enable better moisture retention and absorption of heat units for speedier germination, adds Mr Myhill.

“Before drilling, it’s a good idea to check where the moisture is in the soil. Drilling into some moist areas and some dry ones will lead to staggered germination and uneven crops at harvest time.”

Growing under film helps create more heat units for the plants and is still a good option for growers in colder and more exposed areas. It is also good for growers wanting an early harvest to fit in with rotations.

Film provides a microclimate that encourages successful germination,” says Mr Myhill. “Starch-based films with no plastic content have now been developed so the previous concerns of introducing additional plastic to the farm can be avoided.”