Module 11 Flashcards
Two reasons why soil applied herbicides should be used in a crop are
- After planting soils may be too wet for post applications in a timely manner
- Herbicide may have lower water solubility and not be able to enter the plant leaves
All soil applied herbicides should be incorporated to improve weed control
False
Herbicides applied to soil that have residual activity
Can control seedling weed so that follow up with a post emergence herbicide may not be needed
Soil residual herbicides will be reduce germination on any weed seed in the seed bank, if the weed is on the label for control
False
Order of herbicide sorption to different soil types from LEAST sorbed (most available to the plant and most likely to leach) to MOST sorbed (least available to the plant with the least leaching potential)
1 - Sandy Soil with <1% organic matter
2 - Silty Soils with 2% organic matter
3 - Clay Soils with 1% organic matter
4 - Clay Soils with 2% organic matter
Environmental problems that may occur with herbicides include
- Injury to more tolerant plants if exposed for too long
- Ground water pollution
- Surface water pollution
- Injury to sensitive plants
The amount of soil applied herbicide taken up by a weed is typically 30% or more of the applied dose
False
Thiocarbamate Herbicides
Are taken up by underground shoots through the coleoptile nodes of grasses
Plant uptake of soil applied herbicides
May be from root or shoot uptake
Some herbicides are not water soluble so incorporation into the soil is needed
True
Warm temperatures help in herbicide breakdown in the soil but may also increase volatilization that can lead to offsite non target injury
True
Soil pH
Can lengthen the time to breakdown of certain chemicals in the soil by limiting hydrolysis reactions
Soil Herbicides
Can leach, runoff or be moved on eroding soil but amounts are usually <1% of the total applied
