Syngenta Summer Autumn Guide 2020 - Page 50



GRASS WEEDS
HOW DOES CULTIVATION AFFECT GRASS WEED SEED IN THE SOIL PROFILE?
CULTIVATION YEAR 1
Seeds mixed
in top
12-13 cm
Direct Drill
Seeds buried
to 20 cm
depth
Min-till
Plough
CULTIVATION YEAR 2
Direct Drill
Min-till
Plough
Background population of black-grass seed
Direct Drill
Min-till
YR1 black-grass seeds
Plough
Direct Drill
Min-till
Plough
YR2 black-grass seeds
HOW CULTIVATION IMPACTS CROP ESTABLISHMENT AND WEED SEED MOVEMENT
PLOUGH: Grass weed seeds are buried below 20 cm,
outside the main germination zone. This helps when high
levels of grass weeds have been returned to the surface
from the previous year’s crop, but ploughing each year
returns seeds to the surface that were buried in previous
years. Therefore ploughing should be carefully planned
as part of a long-term rotational strategy.
MIN-TILL: This is the term we use for non-inversion
tillage to around 12-13 cm depth. Some grass weed
seed still remains on the surface, but also mixed all the
way through the profile right down to the cultivation
depth, making it difficult to know how much will
50
germinate in the crop. As it germinates from different
depths, it can emerge over a longer period of time in
the autumn/spring making it more difficult for residual
herbicides to control.
SHALLOW CULTIVATIONS (

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