INTERSPECIFIC COMPETITION BETWEEN SWEET SORGHUM AND WEEDS

While evidence is mounting that sweet sorghum [Sorghum bicolor (L.) Moench], an ethanol crop, may provide an alternative to sugarcane (Saccharum officinarum L.) on sugarcane lands under rehabilitation, little is known of its under production limiting factors (e.g., interspecific competition with weeds). Accordingly, the aim of the present study was to identify the initial mutual interspecific competition between sweet sorghum hybrids and weeds in high infestation situations. The experiment was carried out in pots, using a 5 x 6 factorial design: (i) a sorghum-free control and four sweet sorghum hybrids (CVSW 81198, CVSW 80007, CVSW 80147 and XBSW 82158), besides a control without sweet-sorghum, and (ii) five species of weeds [Cyperus rotundus L.,Mucuna aterrima (Piper and Tracy) Holland, Brachiaria decumbens Stapf, Ipomoea hederifolia L. and Digitaria nuda Schumach ], besides a weed-free control. M. aterrima was the only weed whose dry mass was not reduced by the presence of sweet sorghum. The hybrids of sweet sorghum did not suffer developmental interference from C. rotundus, I. hederifolia or D. nuda. On the other hand, these weeds dry mass was reduced through competition with sweet sorghum. The sweet sorghum cohabiting with B. decumbens or M. aterrima has its aboveground and leaf dry mass reduced. Sweet sorghum is a high competitive and robust plant and, even when under a high weed density, suffers little interspecific interference from certain species of the weed community.