COMPETITIVE ABILITY OF SWEET SORGHUM CULTIVARS AGAINST ARROWLEAF SIDA

Abstract

Weeds infesting the sweet sorghum crop would compete for environmental resources, such as water, sunlight, and nutrients, thereby reducing the crop’s productivity. The objective of this work was to evaluate the competitive ability of sweet sorghum (Sorghum bicolor) cultivars with the weed arrowleaf sida (Sida rhombifolia). The experiments were carried out in a completely randomized design, with four replications. Treatments were arranged in replacement series in proportions of 100:0, 75:25, 50:50, 25:75, and 0:100%, which were equivalent to 20:0, 15:5, 10:10, 5:15, and 0:20 plants per pot of sweet sorghum (cultivars BRS 506, BRS 509, and BRS 511), respectively. The morphophysiological variables of sweet sorghum and arrowleaf sida were determined 50 days after plant emergence. The competitive performance was analyzed using a graphical method that involved constructing diagrams based on relative productivity. The relative indices of competitiveness, clustering, and aggressiveness were also determined. Stem height and diameter were increased for all proportions in the three sweet sorghum cultivars, while leaf area and aboveground dry mass were reduced. The physiological variables were higher or close to the expected for BRS 509 and BRS 511. The competitiveness indices show that the cultivars BRS 506 and BRS 509 were more competitive than arrowleaf sida. In general, cultivars differed in their strategies for dealing with weed competition, with BRS 509 superior overall. However, further field studies are necessary to confirm the superiority of a given cultivar.