|Developments in crop-weed competition research
Comparison of simple yield loss models
At the time of establishment of the Working Group, research related
to crop-weed interactions focused on the construction of robust damage
relationships to support rational decision-making on the use of
herbicides. Multi-location trials were laid out by the Working Group
members (from Finland to Spain and from Italy to the UK and Canada) to
evaluate the yield-loss weed density model of Cousens (1985) and the
relative leaf area model of Kropff & Spitters (1991). The evaluation
confirmed the good descriptive ability of both models (Lotz et al.,
1996). At the same time, predictive ability of both models was found to
be poor and suggestions for improvement were made.
Cousens, R., 1985. An empirical model relating crop
yield to weed and crop density and a statistical comparison with
other models. J. Agric. Sci. 105, 513-521.
Kropff, M.J. & C.J.T. Spitters, 1991. A simple model
of crop loss by weed competition from early observations on relative
leaf area of the weeds. Weed Res. 31, 97-105
Lotz, L.A.P. et. al., 1996. Prediction of the
competitive effects of weeds on crop yields based on the relative
leaf area of weeds. Weed Res. 36, 93-101.
Cultural control measures
In the last decade, interest in weed management strategies that are less
dependent on herbicides has increased. As a result, agronomic measures
to manipulate crop-weed interactions, like competitive cultivars, crop
spatial arrangement and timing, level and placement of fertilizers, have
opened new scope for research in the area of crop-weed interactions. The
same holds for the introduction of intercropping practices to suppress
More attention for population dynamics
In systems that aim at a reduced reliance on herbicides, the time
horizon of interest is extended and main emphasis is given to long-term
management of weed populations. In this situation, the effect of the
crop on the weed, particularly on weed seed production, becomes
increasingly important. Consequently, research on crop-weed interactions
merges with weed population dynamics. In line with this, decision
support models are being developed that model the consequences of
cropping systems on the population dynamics of weeds.
|The following PowerPoint presentation illustrates the developments
described above in more detail.
It has been converted to a pdf