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Sugarcane

Sugarcane fact file

  • 26 million ha of sugarcane are grown around the world
  • 101 countries grow sugarcane
  • 1.8 billion tonnes were harvested in 2012
  • No. 1 country for sugarcane production is Brazil
  • 25% increase in area of sugarcane in Brazil since 2000

Controlling weeds with paraquat and using associated agronomic practices can help overcome several major environmental issues in sugarcane production including:

  • Soil erosion
  • Water contamination by run-off and leaching of agrochemicals
  • Weed resistance to other herbicides such as glyphosate

Less soil erosion

Sugarcane is often grown on sloping ground or on fragile soils. Tropical rainstorms cause a lot of soil erosion. Loss of topsoil reduces fertility and productivity, makes operations difficult where gullies have opened, and the eroded soil blocks water courses. Associated run-off of pesticides and nutrients may also reduce biodiversity and cause eutrophication in lakes and rivers.

When preparing fields for a new crop, instead of plowing, weeds or a legume cover crop grown while the land was fallow can be controlled by a non-selective herbicide such as paraquat. Paraquat has the advantage over systemic herbicides like glyphosate in that it very quickly kills shoots, leaving roots intact to improve soil structure and provide an anchoring effect to resist erosion. Cane setts are then planted in single furrows or narrow strips of tilled soil.

Paraquat does not leach

Paraquat is deactivated immediately on contact with the soil, so there are no run-off, leaching, persistence or root uptake problems to restrict its use. Residual herbicides, which act in the soil on germinating weed seeds, are widely used in sugarcane. However, although these herbicides give long term weed control, they have to move in the soil to be effective, so running the risk of leaching. 

Reduced risk of weed resistance

Weeds reduce sugarcane yields by competing for light, water and nutrients, by harboring pests and diseases, interfere with milling, and limit the number of ratoon crops which regrow from an original planting. 

Paraquat is not systemic like glyphosate, so it can be applied up to the four leaf stage of sugarcane without lasting damage. In some situations the temporary scorching of the crop is even beneficial and stimulates the growth of side-shoots (tillers). Later, paraquat can be used to desiccate the crop by spraying by air 3-14 days before harvest.

Although glyphosate gives good control of perennial weeds, its intensive use can encourage aggressive broadleaved weeds and even weed resistance. Paraquat gives excellent control of a broad spectrum of annual weeds, so it can be alternated with glyphosate to provide effective and sustainable weed control, reducing the risk of resistance.