14 September 2001

Maturity test in the field

CORRECT assessment of maize maturity is vital to achieve an optimum harvest date, but it can be done quickly and easily in the field.

To clamp maize at the best stage means compromising between getting the maximum amount of starch deposited in the grain and retaining stover and leaf quality, says CEDARs Richard Phipps.

"While dry matter content is perhaps the most commonly reported measurement of crop maturity, it is not quick and easy to assess in the field."

An alternative measurement of maturity, which is less dependent on the plants vegetative state, is to examine the starch deposition in the grain. "To do this, snap a maize cob in half and look for the milk line, which is an indicator of starch deposition in the grain. When grains are half to two-thirds full of starch this should equate to about 30% whole crop dry matter content," says Dr Phipps.

But a crop from a staygreen variety may have a lower whole plant DM content when grain is at a similar stage to a conventional one. "It could be about 5% DM lower than a conventional crop with grain at the same DM." &#42