Federico Rolle focuses on weed control after soya harvest

 After harvesting the soya and miaze, it is important to keep the fields free of weeds, as I will not be planting wheat this current year (winter wheat). There is just too much risk of a negative margin.

During this period, my focus is on storing water in the soil for the next soyabean crop and controlling weeds is part of this.

Having no weeds allows us to store more soil water for crops for the next season, because spring-summer weeds accumulate dry matter in autumn in their storage organs; as rhizomes in the case of Johnson grass (Sorghum alepense), or stolons in the case of Bermuda Grass or Commelina.

Flax-leaf fleabane (Conyza bonariensis) is a problem weed throughout the farming region and particularly in some of the fields I manage, due to its ability to spread rapidly and the difficulty to control because of its resistance to glyphosate.

In my case I am applying with very good results 2.5 litrest/ha of sulfosate + 1,2 litres/ha of 2,4D + 8g/ha of metsulfuron, but at a cost of US$30/ha (£20). This is expensive compared with the $15/ha (£10) 3-4 years ago, when I didn’t need to use more applications or 2,4D to control weeds with resistance to glyphosate.

However, it would be a misapprehension that weed problems will be “magically” resolved by herbicides with new modes of action, or new types of glyphosate that “are about to hit the market”. This issue will continue with the current production model of soyabean being the only, or main crop.

The next improvements in weed control may come from breeding and biotechnology and the development of non-chemical methods which, if adopted and implemented correctly, could increase diversity.

This could help decrease the manifestation of resistance problems and herbicide tolerance, and that will undoubtedly favour agricultural production systems in general, including for soybean crops.

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