Agriculture Reference
In-Depth Information
Chapter 12
Cutting Down on Weeds to Cut
a Cleaner Wheat Crop
Drew J. Lyon, Robert E. Blackshaw, and Gurjeet S. Gill
SUMMARY
(5) Integrated weed management (IWM)
systems rely on the use of multiple tactics
for weed control. Tactics include preven-
tion, cultural practices such as crop rota-
tion, mechanical methods such as tillage,
and herbicide application.
(6) The patchy nature of many weed infesta-
tions provides an opportunity to reduce
herbicide use through precision farming
technologies, thereby reducing production
costs and environmental impacts.
(7) In North America, intensifi cation and
diversifi cation of the traditional wheat-
fallow rotation, combined with the use of
conservation or zero tillage (no-till), has
reduced the impact of weeds in wheat. The
benefi ts include increased water storage
and water-use effi ciency, higher annual-
ized grain and forage yields, and greater
net profi tability.
(1) Weeds compete with wheat for various
growth factors, including nutrients, light,
and water, resulting in reduced wheat yield
and diminished profi tability.
(2)
Weeds can compromise wheat grain quality
and marketability by reducing grain protein
content, contributing to dockage and/or
foreign material levels, and by increasing
grain deterioration in storage.
(3)
Herbicides have been hailed as one of the
most important advances in agriculture
and they now typically comprise 20%-
30% of input costs in North American
cropping systems. High input costs, crop
injury and herbicide carryover concerns,
the increasing incidence of herbicide-resis-
tant weeds, and public concerns about the
environmental and human health effects of
pesticides are forcing reassessment of the
heavy reliance on herbicides for weed
management.
(8)
In Australia, widespread development of
herbicide resistance in several important
weed species has forced farmers to better
manage weed seed production. Some of
these management tactics are used in the
rotation prior to the wheat phase (e.g.,
spray-topping pastures or crop-topping
pulse crops), while others such as optimiz-
ing seeding date, seeding rate or crop
density, and cultivar and herbicide choice
are implemented during the wheat growing
season.
(4)
More than 300 unique herbicide-resistant
weed biotypes belong to more than 180
species around the world. The majority of
herbicides used in wheat belong to just two
site-of-action groups: Group 2, inhibitors
of acetolactate synthase (ALS), and Group
4, synthetic auxins. Herbicide resistance in
weeds is a major concern for wheat pro-
duction worldwide.
