lecture 10 Flashcards
3 main tactics of non-herbicidal weed control
1) increasing crop competitiveness
2) preventing weed species dominance
3) limiting weed invasion
6 ways of increasing crop competitiveness
A) species characteristics
-early establishment
B) method of planting
-wide rows = less crop competition against weeds
C) seeding date
-when conditions suit crop not weed
D) seeding rate
- when conditions suit crop
- delayed seeding allows for weeds to emerge than control
E) Fertilizer
- rate/ timing
- excess N can benefit weed
F) tillage
- destroy weeds / dormant roots
cultivators
- degree of soil mixing depends on angle of blade
- tend to sever roots of large weeds, uproot small weeds and bury both in soil
Discs and rotary tillers
Chop up weeds and crop residues and mix them with soil
conventional seeding
uses multiple tillage passes (fall, spring) prior to seeding
Reduced tillage
Reduction of some tillage passes (usually fall is the first to be removed)
direct seeding (no till)
seeding and fertilizing is completed in a single operation with no additional tillage
effect of deep rooted perennial weeds from tillage
replacement of shoots removed by tillage
effects of shallow rooted perennials by tillage
fragmented by tillage - short term benefit, may be a dispersal technique
mulches (general)
physical prevention of weed emergence
organic mulches
straw, clippings, leaves
weed control depends on thickness and durability
may reduce soul temp
may reduce yield due to competition
plastic mulches
plastic sheeting within row
black = doesn’t warm soil
clear = let’s red light in –> weed seed germination
living mulches
cover crop grown and harvested with crop
reduces light penetration to ground
can reduce yield due to competition
- preventing species domination
A. crop rotation
B. use of ‘smother crops’
C. other methods
crop rotation - variations in timing of:
planting, harvesting, tillage, herbicide application
crop rotation - variations in methods of:
tillage, planting, weed control
perennial forage ‘smother crops’
strong competitors
deep rooting
frequently harvested
annual forage ‘smother crops’
strong competitors
fall cereals
frequently harvested
grazing forage crops
reduces weed seedbank input
flaming - other methods
selective or non- selective
in crops where meristem is underground or crops are tall and woody
grasses usually not effected
mowing - other methods
repeated mowing needed to kill perennials
clipping weeds above crop canopy
solarization - other methods
covering moist tilled soil with plastic for 2-4 weeks
kills imbibed seeds, rhizomes, fragments
burning - other methods
removes vegetation
burning straw can kill seeds
may break dormancy
use of certified seed - prevention
seeding contaminated seed one of the most common ways of introducing weeds
