Agronomy Library > Fertility & Fertilizer Placement

Predicting Weed Emergence Patterns in Direct Seeding - Direct Seeding Advantage 2005
Author: Kristin Hacault, BASF Canada
Date Created: November 22, 2005
Last Reviewed: February 27, 2009
Successful crop production in western Canada is dependent upon a producer’s ability to effectively control weed infestations, and determining the emergence timing of weed species may be used to enhance the efficacy of weed control practices (Bullied et al. 2003). For example, being able to predict weed emergence patterns in response to tillage operations could coordinate the timing of seedbed preparation and optimize the timing and rates of herbicide applications (Grundy 2003). Weed emergence is determined primarily by soil temperature and soil moisture status, which are influenced by environmental conditions and soil management, such as tillage (Martens 2004).  Soil moisture and temperature affects the germination, emergence, and the number of weed species present in annually cropped fields (Boyd and Van Acker 2003). The timing and type of tillage practiced modifies weed seed placement within the soil profile and alters the soil conditions to which weed seeds are exposed (Boyd and Van Acker 2003). Practical predictive weed emergence models can aid in the use of weed emergence timing information (Forcella et al. 1997).  Models such as WeedCast, developed by scientists at the USDA in Marshall, Minnesota and the University of Wisconsin (Archer et al. 2001), and the University of Manitoba Weed Emergence Calculator (Martens 2004) have been developed as convenient and easy to use tools that assist farmers in making management decisions based upon weed emergence timing under various soil disturbance practices and environmental conditions. Over the course of the past few years several studies were conducted at the University of Manitoba that aimed to predict the emergence period of weed species as a function of cumulative soil growing degree days (GDD) in various tillage and cropping systems (Boyd and Van Acker 2003; Bullied et al. 2003; Reid and Van Acker 2005; Hacault and Van Acker 2006; Lawson 2005).  These studies were carried out to provide growers with valuable information on the emergence patterns of weed species in annual crops and aid in managing weed infestations. It is important to identify when, in their lifecycle, given weed species are most susceptible to a wide range of control measures. By targeting weeds at appropriate stages within their development, farmers can increase herbicide use efficiency and perhaps reduce herbicide use. This paper will primarily focus on the work of Hacault and Van Acker (2006), who investigated the emergence timing of dandelion (Taraxacum officinale) under reduced tillage conditions in spring wheat fields in southern Manitoba. Open the PDF for the complete paper