Simulation of crop-weed competition : Models and their applications

Abstract

Competition between crops and weeds is a complex phenomenon. Comprehensive, process-oriented simulation models which treat competition in a mechanistic rather than an empirical fashion, can offer insight into relationships among competition, crop and weed density, relative time of emergence, various morphological and physiological traits, and resource levels. They can also be used for prediction as part of a Systems approach to weed management. This paper reviews the features of a number of recent simulation models of crop-weed competition, the species for which they have been parameterized, and their applications. To date, these models have been used primarily to predict crop yield losses due to weed competition. Their ability to simulate weed seed production in response to the environment has not been exploited. The next step is to link simulation models of crop-weed competition to weed population dynamics models, in order to improve our ability to predict the effect of various weed management strategies over time. Advantages and drawbacks of a modeling approach to weed management problems are discussed.

Modelling crop-weed competition: Why, what, how and what lies ahead?

“…Many of the earlier mechanistic models were created as extensions of singlespecies crop simulation models, with additional routines to represent how resources are shared between species (Park et al, 2003;Deen et al, 2003;Weaver, 1996;e.g. Orwick et al, 1978;Ryel et al, 1990;Kiniry et al, 1992;Kropff and Van Laar, 1993;Weaver et al, 1994;Chikoye et al, 1996;Lundkvist, 1997).…”

Field evaluation of regression equations to estimate crop yield losses due to weeds

“…There is an increasing consensus among weed ecologists that some of the shortcomings associated with using empirical yield loss models alone may be overcome by adopting a more mechanistic modeling approach to weed/crop interactions such as adapting existing crop growth models to include competition from weeds (Weaver 1996;Swanton et al 1999;Bastiaans et al 2000). Several of these simulation models have been evaluated with reasonably positive outcomes (McDonald and Riha 1999;Vitta and Satorre 1999;Deen et al 2003).…”

The Relationship Between Patch Spraying Cost and Target Weed Distribution

“…Not treating a near threshold weed population may affect whether or not a threshold will be exceeded in subsequent years due to increases in weed seedbank. Weaver (1996) discussed the importance of seed production by threshold density weed populations, emphasizing the importance of seed viability, dormancy and longevity. Long-term weed management programs must consider weed seed production, as well as yield losses to permit accurate cost estimation and to increase the likelihood that the threshold criterion is adopted by producers.…”