Weeds in sugarcane fields
1994
Kleopan Suwanarak (Department of Agriculture, Bangkok (Thailand). Botany and Weed Science Div.)
Weed Species and their distribution throughout the sugarcane cultivated areas were surveyed from 1975 to 1988. At least 20 broadleaves, 16 grasses and 4 sedges belonging to 15 families were complied and viewed as common weeds. Variation of soil type, moisture and fertility of soil in the different planting regions seems to affect weed species and the density of distribution. Species such as Cyperus rotundus, Eleusine indica, Dactyloctenium aegyptium, Echinochloa colona and Pennisetum spp., however can adapt to a wide range of environmental changes and so become the dominant weeds throughout the sugarcane cultivating areas. Most weed species tend to have higher density and biomass per area in the rainy season than in the late rainy and dry season. Weed density and biomass increased from 53.9 plants/square m and 8,215 kg/ha in 1975 to 72.8 plants/square m and 12,338 kg/ha in 1985. Even though in 1985 the percent frequency of sedges was higher than that of grasses and broadleaves, the potential coverage of grasses was greatest of the three when evaluated by the density and biomass per area. The seed reservoir in soil is generally the main source of new infestation by annual weeds. Soil collected from a Suphan Buri sugarcane field at the depth of 0-5 cm was tested for the amount of viable seeds, the number was estimated to be 1,106 seeds/square m based on the number of emerged seedlings at the end of the fifth week of the emergence period. This number was much smaller than that described in other reports, perhaps because some viable seeds did not emerge because the environment and/or time of collection were not optimal. Conventional tilling practices as well as long term use of herbicides may also be involved, however. This study could be an important first step in understanding the dynamics of weed populations in order to manage them successfully in sugarcane.
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