Agriculture Reference
In-Depth Information
Tillage intensity affects weed communities in
agroecosystems
Robert E. Blackshaw
Weed Management Research, Agriculture and Agri-Food Canada, P.O. Box 3000, 5403 1st Avenue
South, Lethbridge, Alberta T1J 4B1, Canada
Introduction
Farmers must continuously deal with weed infestations in agroecosystems and
their importance is reflected in the amount of manual labour, herbicides and
other measures used for their control. Pimentel et al. [1] estimated costs of
invasive plants on agricultural land in the USA at over $34 billion annually.
Herbicides typically comprise 20-30% of crop input costs in North America
[2]. In Canada, over 80% of total pesticide sales are herbicides and they
account for over $1 billion in annual sales [3].
Changing tillage practices on the Canadian prairies
The Canadian Prairies is a large area of 35 million ha of crop land that has
been subdivided into eight ecoregions with soils commonly being Aridic and
Typic Haplustolls [4, 5]. Historically, this region has been dominated by
spring cereal production with fallow being a common part of the rotation. The
primary limiting factors for crop production are low annual precipitation and
a short growing season. Annual precipitation ranges from 350-550 mm and
the frost-free growing season ranges from 90-130 days depending on latitude
[6, 7].
Tillage intensity in Canadian Prairie crop production systems has markedly
decreased during the last two decades as a means of reducing soil erosion, as
well as increasing soil moisture availability, crop yield and economic return
[8-10]. In this region, conventional tillage typically consists of both a fall and
spring operation with either a sweep-plow or tandem-disk prior to seeding
spring crops, and tillage is used to control weeds in fallow. Minimum-tillage
consists of only one tillage operation performed shortly before seeding, with a
combination of herbicides and tillage being utilized to control weeds in fallow.
In zero-tillage systems, crops are planted directly into the previous crop's
stubble with a minimum amount of soil disturbance (<30%) and herbicides are
exclusively used for fallow weed control. A recent survey indicated that 31%
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