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Maize - Do Not Neglect Weed Control

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By Rufus Ulyet 3 years ago

Maize has traditionally been a neglected crop in terms of weed control.

Historically, Atrazine was universally applied and was very effective on many broadleaved and grass weeds, Black Nightshade and Fathen were not well controlled and later herbicides had enhanced activity against those weeds. Following the revocation of Atrazine, many replacement herbicides had little or no activity on grass weeds.

For example Prosulfuron, Bromoxynil & Mesotrione had very limited activity on grass weeds. The continual use of such herbicides has meant that grass weed and in particular Annual Meadowgrass has proliferated in subsequent maize crops.

The tendency to grow maize on the same fields for consecutive seasons has exacerbated the build-up of grass weeds. In Blackgrass areas, the use of maize as a break crop has again highlighted the need for effective control of this difficult weed in the rotation. The maize crop does create the opportunity to use an alternative active ingredient against Blackgrass.

Weed Control Case Studies

In Worcestershire, we have large areas of clay soils which favours Blackgrass and this season I have adopted the policy, in appropriate situations, of using Calaris aMaize  - Weed Controlnd Entail applied post  emergence to maize at the 3 – 4 leaf stage of the crop. There were two instances which demonstrated the effectiveness of this approach:

Farm 1 - Maize had been grown on the same fields for five years and in 2015 a carpet of Annual Meadowgrass was apparent together with broad leaved weeds. Once the Calaris/Entail mix had been applied, control of all weeds was nearly 100% effective. The fields on which the application took place produced an excellent crop of maize – largely due to the reduction in weed competition.

Farm 2 - A large arable enterprise was growing maize as a break crop. All this land had high populations of Blackgrass and Wild Oats and it was vital to control these weeds in the maize. The application of a tank-mixture of Calaris and Entail was extremely successful, the fields were sown with Winter Wheat following the maize harvest and early indications suggest that there is a low level of Blackgrass infestation. It is important to have experience of the weed history of fields to be able to predict and plan herbicide strategies. There are a variety of approaches available, but it is clear grass weeds have now become an increasingly important problem and cannot be ignored.

Consider all the Factors Weed control is one aspect of maize agronomy but there many other factors which must be considered. A soil analysis is essential to determine pH and phosphate & potash indices. The nutrient value of any applied FYM needs to be considered when deciding fertiliser applications of N, P & K. Seedbed quality is always of vital importance, and maize will not tolerate poor seedbeds.

The risk of pest damage has to be assessed and following established grass wireworm may cause a problem, the only chemical control for which is a seed treatment. Last but not least comes variety choice. The variety of maize sown is important but the best variety in the world won’t produce an acceptable crop if the issues above are not dealt with satisfactorily.

Written by Rufus Ulyet - Wynnstay Agronomist