1986 Volume 31 Issue 4 Pages 287-293
The nature and extent of competition between sugarcane and Bidens were investigated. Cane was grown by the conventional cultural practices either alone or in competition with Bidens and the weed was removed at an interval of from 30-60 days after seeding to determine the effect of prolonged weeding on growth of the crop.
For cane, the relative light intensity at 30 days after planting was 90% in the middle of the hills and 100% in the middle of the groove between the rows. The relative light intensity then decreased sharply, the results at 120 days after planting being 2.5% in the middle of the hills and 11% in the middle of the groove. The growth of Bidens main stem length was considerably less than that of cane plant length until up to 30 days after seeding but this difference became less marked at subsequent stages of growth. The growth of cane plant length was further suppressed as the period of weeding was prolonged.
Cane leaf area, leaf blade dry weight and specific leaf area were largest in the pure plot (weedfree plot) and decreased in the mixed plots (plot with weed competition) as the period of weeding was prolonged. Main stalk leaf number and tiller number were large in the pure plot throughout the period of growth and became smaller in the mixed plots as the period of weeding was prolonged.
Main stalk weight and tillering stalk weight, the major yield-controlling elements, were largest in the pure plot and decreased in the mixed plots as the period of weeding was prolonged. Weight values in the mixed plot left unweeded for 120 days after planting were as low as about one-fifth and about one-thirty-eighth, respectively, of the pure plot results.
The severity of competition from Bidens was clearly indicated by the fact that the growth of cane was suppressed more as the period of weeding was prolonged and suppression by the weed reached nearly 80% in the plot left unweeded for 120 days after seeding. In contrast, suppression by the crop was only 10% at 60 days after planting with a further decrease to about 4% in the plot left unweeded for 120 days after planting.
Since Bidens damage becomes serious at 60 days after emergence, it is recommended that the weed be removed earlier (at least within 45 days of emergence) in order to prevent cane yield reductions.
