New tool gives greater precision in maize variety choice

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A new free online tool from LG Seeds will help farmers select the maize varieties best suited to their location and prevent problems associated with delayed maturation.

Using Met Office data, the tool maps the average Ontario Heat Units (OHU) accumulated over the last 10 years using a 5km grid. Armed with actual OHU data for their postcode, farmers will be able to select varieties which will mature within the OHU available. The LG Seeds maize heat map is accessed at

“OHU’s are the internationally recognised system to show if maize can be grown successfully in a particular location, Tim Richmond, maize product manager with LG Seeds explains. “Using the online system, farmers can more accurately identify the maturity class they should go for and help manage the risk when choosing varieties.

If there are too few OHU’s, crops will struggle to mature which can lead to a number of problems. A delayed harvest will potentially lead to harvesting in more difficult conditions, increasing the risk of damage to soil structure. In addition, it will reduce the opportunity to establish a successor crop, leading to stubbles being over-wintered with a greater risk of soil run-off. From a herd point of view, a delayed harvest will mean maize silage is later going into the diet.

Mr Richmond says varieties differ in the number of OHU’s they require to mature and this is why it is important to choose varieties that will mature within the heat units typically achieved in the locality. He says very early varieties require 2500-2750 OHU, for early varieties it is 2750-2900 OHU while late varieties require more than 2900 OHU.

“We recommend selecting varieties which can be grown comfortably within the average site OHU as this minimises the risk of a late harvest or an immature crop. It is better to err on the side of caution than to stretch the point, because there can be extreme years.

“If the average OHU postcode score is close to 2750, it may be better to select a variety with a lower score like Ambition (2,720 OHU’s) that will mature earlier, rather than a higher scoring variety that is slightly later maturing.

“Once a shortlist of varieties have been selected that will mature within the average OHU’s received, look to choose the variety which best combines good levels of starch and high cell wall digestibility with high dry matter yields to deliver a quality silage to drive production and intakes,” he advises.

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