Start Date

20-11-1996 12:00 AM

Description

Traditional methods of preplant herbicide application often involve a broadcast spray followed by one or more incorporation passes. Incorporation reduces the amount of crop residue on the soil surface, which can lead to increased soil loss through wind and water erosion. Incorporation also distributes the herbicide more evenly throughout the soil profile, reducing chemical concentrations in the surface mixing zone. Chemicals located within the 1-2 em mixing zone contribute to herbicide losses with surface runoff (Mickelson et al., 1983; Baker et al., 1979). Conservation tillage, as defined by leaving a minimum of 30% of the soil surface covered by crop residue after planting, allows for incorporation of herbicides while still leaving adequate residue on the surface to reduce erosion losses. Although incorporation has been shown to be extremely effective in reducing surface runoff losses of herbicides, it also is the major contributor to reduced residue cover. No-till, the extreme end of conservation tillage, uses no tillage and maximized residue cover for maximum erosion control. Unfortunately, due to surface application of herbicides, no-till often prevents the use of the more volatile and moderately adsorbed herbicides. In some cases, no-till can increase herbicide concentration and losses with runoff water when compared to conventional tillage (Mickelson et al., 1995).

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Nov 20th, 12:00 AM

Subsurface Application of Herbicides

Traditional methods of preplant herbicide application often involve a broadcast spray followed by one or more incorporation passes. Incorporation reduces the amount of crop residue on the soil surface, which can lead to increased soil loss through wind and water erosion. Incorporation also distributes the herbicide more evenly throughout the soil profile, reducing chemical concentrations in the surface mixing zone. Chemicals located within the 1-2 em mixing zone contribute to herbicide losses with surface runoff (Mickelson et al., 1983; Baker et al., 1979). Conservation tillage, as defined by leaving a minimum of 30% of the soil surface covered by crop residue after planting, allows for incorporation of herbicides while still leaving adequate residue on the surface to reduce erosion losses. Although incorporation has been shown to be extremely effective in reducing surface runoff losses of herbicides, it also is the major contributor to reduced residue cover. No-till, the extreme end of conservation tillage, uses no tillage and maximized residue cover for maximum erosion control. Unfortunately, due to surface application of herbicides, no-till often prevents the use of the more volatile and moderately adsorbed herbicides. In some cases, no-till can increase herbicide concentration and losses with runoff water when compared to conventional tillage (Mickelson et al., 1995).

 

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