Enhancing the competitive ability of crops - Ecological Management of Agricultural Weeds - page 280

Figure 6.4 Replacement series diagrams showing the effect ofchanging crop
density on crop yield when (a) the crop is more competitive than the weed and (b)
the crop is less competitive than the weed.The curves show the yield response of
the crop and weed.Numbers in parentheses correspond to the situation where
halfthe weeds are removed randomly at or before emergence.(Modified from
Mohler,1996.)
100 crop plants m 2 corresponds to a mixture with 33.3% weed and 66.7%
crop (Figure 6.4b).In this case,doubling crop density to 100 plants m 2 has an
even greater effect on yield (183 kg ha 1 increase rather than the 160 kg ha 1
increase observed at the higher weed density).This occurs because the interac-
tion shifts rightward onto the more steeply rising portion of the curve.