WEED TOLERANCE, SUPPRESSION AND GRAIN YIELD OF INTER AND INTRA SPECIFIC RICE VARIETIES IN NIGERIA

Field experiment was conducted in wet seasons of 2006, 2007 and 2008 to ascertain the weed tolerance, suppression and productivity of inter and intra specific rice varieties, FARO 43, 44, 48, 49 and 55 in Minna, Southern Guinea savanna of Nigeria. The rice varieties were sown at 75cm inter-row and 25cm intra-row distance. The experiment was laid out in a randomized complete block design (RCBD) and replicated four times. The weed types prevalent were 75, 21 and 4% broadleaves, grasses and sedges, respectively. However, broadleaves that were observed to occur in high density were Ageratum conyzoides Linn., Cassia mimosoides Linn., Chromoleana odorata L., Comelina spp., Gladiolus spp., Hyptis suaveolus Poit, Spegilia authelmia Linn., Tephrosia bracteolata Guill Poir and Tridax procumbens Linn., while the grasses had Brachiara spp., Paspalum spp., Pennisetum pedicellatum Trin and the Setaria pumila (Poir) Reom and Schult were ubiquitous and the sedges were generally low in occurrence. The mean weed density for the three years indicated a significant lower density in FARO 55 compared to FARO 48 at 4 weeks after sowing (WAS) and significant lower weed dry biomass in FARO 44 compared to FARO 43 at the same period. At 10 WAS FARO 43 has significantly lower weed density compared to other varieties while FARO 55 was significantly more suppressive by producing significantly lower weed dry biomass. At 16 WAS, FARO 43, 44 and 55 were at par in the level of weed infestation, however, FARO 55 was significantly most suppressive in terms of weed dry biomass production. FARO 44 had significantly higher number of rice tillers at 9 WAS and lower panicle weight. All the rice varieties had similar grain yield ha^-1; however, FARO 48 had significantly higher weight for 1000 grain weight. It is therefore concluded that all the rice varieties were tolerant to weed infestation; however, FARO 55 was significantly much more suppressive than the other varieties.