VL4, VL5 - 10.10.24/17.10.24 Integrated weed management Flashcards

1
Q

Key components of Integrated Weed management IWM

A

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

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2
Q

Residue management at / after harvest

A

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

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3
Q

Options in residue management

A

Chaff spreader
Heavy harrow

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4
Q

Tillage

A

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)

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5
Q

Possible objectives of tillage

A

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

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6
Q

Problems / dangers with tillage

A

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

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7
Q

No tillage, dierct seeding, zwero tillage

A

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

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8
Q

Bilder

A

See pictures in slides

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9
Q

Comparison Intense tillage - Extense (no-)tillage

A

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

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10
Q

Reduced tillage systems

A

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).

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11
Q

Conflict of interest - herbicide reduction and soil and resource conservation measures

A

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.

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12
Q

Conservation agriculture

A

p. 32

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13
Q

Conclusions on use of cover crops

A

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

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14
Q

Stale (false) seedbed

A

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

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15
Q

Influence of sowing technology on weed populations

A

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
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16
Q

How harvest technology influences weed populations

A

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.