Pre-harvest crop desiccation (also siccation ) refers to the application of a herbicide to a crop shortly before harvest. The herbicide most widely used is glyphosate, while use of diquat and glufosinate is much more limited. For potatoes, carfentrazone-ethyl is used. Other desiccants are cyanamide, cinidon-ethyl, and pyraflufen.
Uneven crop growth is a problem in northern climates, with wet summers, or poor weed control. With desiccation a number of advantages are cited: More even ripening is achieved and harvest can be conducted earlier; weed control is initiated for a future crop; earlier ripening allows for earlier replanting; desiccation reduces green material in the harvest putting less strain on harvesting machinery. Some crop may be mechanically destroyed when crop desiccation machinery moves through the field.
The application of glyphosate differs between countries significantly. It is commonly used in the UK where summers are wet and crops may ripen unevenly. Thus in the UK 78% of oilseed rape is desiccated before harvest, but only 4% in Germany. Other countries have banned desiccation practices, such as Austria and Switzerland.
- Oilseed rape
- Potatoes (not with glyphosate)
Glyphosate is applied to plants just before harvest and absorbed by plants; it cannot be washed out prior to human use. Herbicides can also reach humans through meat and milk of cattle that has been fed herbicide-treated fodder. It has been identified in the urine of urban dwellers who do not handle glyphosate at concentrations of 0.5-2 ng/ml, much higher than allowed in drinking water (<0.1 ng/ml).
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- "The agronomic benefits of glyphosate in Europe". Monsanto Europe SA. February 2010. Retrieved 2 June 2013.
- "Desiccation programmes". Potato Council. 2 August 2011. Retrieved 2 June 2013.
- Brändli D, Reinacher S (January 2012). "Herbicides found in human urine". Ithaka Journal. Retrieved 3 June 2013.
- Industry Task Force on Glyphosate (21 November 2013). "Preharvest weed control and desiccation.". Retrieved 15 January 2014.
- Industry Task Force on Glyphosate (8 January 2014). "Preharvest use of glyphosate:Recent Austrian decision.". Retrieved 5 January 2014.