VL4, VL5 - 10.10.24/17.10.24 Integrated weed management Flashcards
Key components of Integrated Weed management IWM
Identification of the weeds present
rop residue management
Competitive crop variety
Crop rotations
Effect of soil cultivation methods/cropping system on weeds
Stale seedbed/weed control before sowing
beneficial effects of cover crops
Mechanical weed control methods
Economic treshold
Map heavy infestations of particular weeds for patch treatments
There are beneficial species among the weed populations
Weeds = wildlife resource
Residue management at / after harvest
Volunteer crops in piles/swaths of straw and chaff (e.g. visible after harvest of winter wheat) germinate
When residues are evenly distributed, threshold for control is not reached, when not distributed, threshold for control is reached wihtin the swaths
Options in residue management
Chaff spreader
Heavy harrow
Tillage
basic soil cultivation and seedbed preparation before sowing are the most important measures for mechanical weed control
Thanks to tillage, the original vegetation has developed into today’s vegetataion
The weed flora of the field (mostly annual seed weeds) is adapted to tillage (bligate dormancy ensures survival of the species in a tillage system. It is broken in the soil by moisture, cold and - after tillage - by light)
Possible objectives of tillage
Einjährige Unkräuter bis 2-Blatt-Stadium bekämpfen
Einjährige Unkräuter grösser als 2-Blatt-Stadium bekämpfen
Mehrjährige Wurzel-Unkräuter bekämpfen
Bodenverdichtungen läsen
Saatbettbereitung
Unkrautkur vor Saat
Horizontale Verteilung von Pflanzenresten
Vertikale Verteilung von Pflanzenresten
Ausebnen der Bodenoberfläche
Depending on objective different machines can be used
Problems / dangers with tillage
Intensive cultivation (upside-down / moldboard plow tillage, high axle loads, PTO-driven soil cultivation equipment) haas recently (~30 years) led to increasing environmental problems: Soil erosion, compaction, clogging, water pollution
Today, tillage can often be done without regard to soil / weather conditions
Possible solution: reduction of tillage, no.till = most extreme but most effective measure -> conservation / regenerative agriculture
No tillage, dierct seeding, zwero tillage
weed seeds are no longer transported in the soil profile (dormancy is no longer broken)
weed seeds accumulate in the top layer of the soil
the reserve organs in the soil are no longer regularly destroyed
the soil is usually covered by a distinct mulch layer
majority of seeds are dormant, dormancy is broken when seeds come in soil, when seeds come on surface again through ploughing light and other things can induce germination
Bilder
See pictures in slides
Comparison Intense tillage - Extense (no-)tillage
P. 25
Soil cover with plant residues: few - dense
Risk for soil erosion and clogging: high - low
Position of weed seeds in the profile: dispersed over the profile - on the soil surface
Typical weed species: annual dicotyledons, grasses (monoculture CR), perennial species (organic farming) - Surface germinatiors, Anemochorous species, volunteers, perennial species
Total weed abundance: rather high - with dense plant residues/cover crops rather low
Type of herbicide: Soil herbicide - leaf applied herbicide
Weed control at seeding of the crop: tillage - often non-selective herbicides
Reduced tillage systems
weed control by the plow is eliminated and must be replaced (non- selective herbicide, green manure, plant residues, multiple surface tillage)
equipment commonly used in plow cultivation for mechanical weed control is usually useless because of the mulch layer
Herbicides are often absorbed by the mulch layer and the effect of soil herbicides is usually reduced. Therefore, contact herbicides should be used more frequently where possible.
Cereal and foliar crops should always be alternated (volunteer crops)
when selecting varieties, care should be taken to ensure rapid youth development
Certain herbicides can lead to post-emergence problems under unfavorable conditions (late application date, dry weather) (especially sulfonylureas or triketones).
Conflict of interest - herbicide reduction and soil and resource conservation measures
Today, weeds can be efficiently controlled by herbicides or physical measures, mainly tillage and mechanical weeding.
Destruction of the soil surface structure requires energy (fuel), time, and increases the risk of soil erosion (mainly water, but also wind) and silting.
An ideal cultivation system ensures: - good germination/growth conditions for the crop - soil structure as in no-till systems
- weed control without herbicides
- highest possible biodiversity
- all rules for crop protection respected
- maximum availability of plant nutrients.
Today, no cropping system meets these requirements.
Conservation agriculture
p. 32
Conclusions on use of cover crops
Mixtures produce more biomass than monocultures and suppress weeds more efficiently.
Mixtures are able to compensate for different growing conditions (moisture, soil, exposure, nutrients,…) within fields.
Seed rate of individual species in mixtures with 2-3 species = seed rate in monoculture / number of mixture partners.
Seed rate of individual species in mixtures with > 3 species = seed rate in monoculture / (number of mixing partners + 1).
Green manures can be controlled mechanically (knife roller, mulcher) when stems are woody and plants are flowering (=vegetative phase completed).
Mixtures with many species are more difficult to control than those with fewer species (different ideal times for control).
cover crops should be high
Seed as early as possible, best is before potential weeds germinate
Stale (false) seedbed
Reducing the weed seed density in the topsoil (<5cm)
Repeatedly tilling the soil surface (<5cm) between primary/secondary tillage and seeding.
Germinated weeds are killed and new seeds will germinate after tillage.
Suited implements: Everything that allows tilling the topsoil only
should be used in cropping systems which work without herbicides
Heavy harrow used as a tool for stale seedbed
Influence of sowing technology on weed populations
Sowing time:
* in spring, late sowing causes faster youth development = better competition against weeds
- early sowing (of winter crops) promotes rapid development and weed suppression in spring
- To control weeds germination in fall (e.g. foxtail) can be controlled by deliberately shifting the sowing time (late sowing in early November after weed germination)
- Seed row spacing (narrow rows cause greater competition, wide rows allow harrowing).
- Seed depth (shallow seeding results in faster emergence, deep seeding results in better water supply).
- Herbology vs. yield increase
How harvest technology influences weed populations
Time
Technique (cutter bar, silage; abroad swath threshing, stripper)
Distribution of individual species in the field (e.g. dock)
Straw management (concentration of weed seed density in swath, chaff spreader, straw distibutor)
Potential to reduce seeding: chaff collectors/chaff treatment.