Farmers weekly 13-07-2018
Tips to manage maize without the rain
Maize growers are being warned that drought like conditions could hinder crop pollination. Warm weather is pushing many crops forward, meaning maize will start pollinating any time from 20 July until the end of the month. However, each day of moisture stress during pollination can reduce yields by 3-8%.
Agronomist Simon Draper of the Maize Growers Association says he is seeing crops at the two extremes this year.
"This warm weather is perfect for maize, as long as the crops can get their roots down. If we continue with this weather and the crops have some moisture, it will be a big crop," he says.
"The issue is where the soil structure is not good enough and the roots cannot get down to the water. This is where we are seeing stressed crops with leaves rolled up."
Maize crops grown on land with little organic matter are also showing signs of stress, says Grainseed technical director Neil Groom.
"Where organic matter is less than 1 % the land is now droughted and the leaves are twisting up," he says.
Water stress at pollination delays the silks from emerging (female part of the crop), reduces silk elongation and inhibits embryo development after pollination.
The silks may also become non-receptive to pollen germination. This will affect the number and quality of the kernels. Usually, the tassels (male part of the plant) start shedding pollen a day before the silks emerge.
When to irrigate
Once the tassels can be felt running up the stover, they are about a week away from
pollination. It is at this point that drought-ridden crops will need water, says Mr Groom.
Although irrigation may be impractical for many, those that have abstraction licences and equipment should consider applying 2 inches of water one week before the tassels start to shed pollen, Mr Groom added.
"Good pollination is important as 50-60% of the total maize yield comes from the cob and for this, you need good pollination and grain set," he says.
Farmers applying fertiliser to their crops should also be cautious to avoid scorching the leaves.
Mr Groom explains: "If you are using granular fertiliser and the plants are dry, the prills will usually bounce off the leaves on to the ground. However, if there's some dew on the leaves the prills can stick and burn them.
"You can now get nitrogen sources that you can spray without any scorching, so it's worth considering something like Efficient 28, which is a liquid foliar nitrogen fertiliser based on urea polymers of variable lengths.
"The longer chains slow the breakdown, resulting in a phased release of nitrogen over six to eight weeks."