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8 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Factors that's affect soil-residual herbicides |
Mobility Applied evenly Adsorbed Micro organisms Leached Depth protection Volatile |
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Mobile |
Enter via the roots and move with the water from the roots to the leaves in the xylem Generally applied to bare soil and they kill weeds as they germinate Taken up by weed seedlings when they are absorbing water from the soil Not effective in dry conditions |
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Applied evenly |
Any gaps in the herbicide cover will allow seedlings in that area to establish Herbicides applied at high water rates to ensure a good coverage of soil The ground should not be covered in crop residues as these can be moved via wind or machinery leaving gaps in herbicide cover Herbicide must be deep enough in ground to ensure root contact This some rainfall is required to wash the herbicide into the soil and activate it |
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Adsorbed |
Herbicide susceptible to being adsorbed to the surface of particles Soils with large surface areas such as clays and organic matter can reduce the amount of herbicide available to kill weeds High application rates required |
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Micro organisms |
Herbicide eventually deactivate by micro organisms that break down the molecule to obtain nutrients and energy Last longer at high application rates |
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Leached |
Some leaching required to get in root zone but to much leaching causes it to be leached from root zone |
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Depth protection |
Some residual herbicide are selective because they remain near the surface of the soil and do not move down into the root zone of the crop. Used in deep rooting crops such as trees and Lucerne. Excessive leaving in these situations will lead to crop damage. Herbicides used for depth protection are usually low in solubility |
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Volatile |
Left on surface can lead to herbicides been lost as gas. Herbicides susceptible to this need to be cultivated into ground |
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