Preliminary Investigations into the Competitive Effects and Control of Cyperus Rotundus L. in Sugarcane Fields

The ~umose of the four ex~eriments re~orted here was to Preliminary results of four experiments designed to determine the competitive effects of Cyperus rotundus L. on sugarcane and to investigate methods of controlling this weed, are reported. A trial in which a plant crop of varieties N13 and N8 was grown under rainfed conditions showed that competition from C. rotundus caused decreases in yield of 85 and 83% respectively. In a second trial under irrigation, stalk elongation and tillering were slower in plots of plant cane which contained C. rotundus. Methods of re-establishing sugarcane which showed effective control of C. rotundus include: minimum tillage with a second application of glyphosate (Roundup), conventional tillage with a single or repeated application of Roundup onto emerged C. rotundus plants; and to a lesser extent, the use of Eptam Super at the time of planting. Two trials in ratoon cane showed that many treatments provide short term control of C. rotundus populations, even in the following ratoon. The best treatments were repeated applications of Roundup, hexazinone (Velpar) and MSMA, and hand hoeing. The growth of ratoon sugarcane was not improved by controlling C. rotundus, but no treatment eliminated C. rotundus completely. Crop growth will be monitored in subsequent ratoons to assess the effect of reduced C. rotundus populations.