Spatial and Temporal Effects of Kenaf (Hibiscus cannabinus L.) Cultivation on Weed Dynamics in Southern Agro-ecologies of Nigeria

Abstract

Weed spectrum in Kenaf fields revealed the heterogeneous flora richness of agro-ecologies and potential weed challenges. A study was conducted in the Institute of Agricultural Research and Training (IAR&T), Obafemi Awolowo University Ibadan and other substations (Ilora, Ikenne and Kishi).  The effects of varied kenaf planting dates, genotypes and locations on weed dynamics and potential weed problem was investigated. Five Kenaf genotypes (Cuba 108, Ifeken DI 400, Ifeken 100, Ifeken 400 and Tianung 2) were planted. It was a 3 x 4 x 5 factorial experiment arranged in Randomized complete block design (RCBD) with three replicates. Forty five (45) weed species were identified across seventeen (17) plant families. Weed morphology comprised of broad-leaf weeds (71.11%), grass weeds (17.78%), sedge (6.67%) and spiderwort (4.44%). Abundance        of broad-leaf weeds (71.11%) mostly annual, reflected regular weed control from frequent     cropping patterns and agro-ecological variations. Panicum maximum, Ageratum conyzoides,  Tridax procumbens, Mitracarpus villosus, Spigelia anthelmia L. and Mimosa pudica were present in the locations. Commelina erecta, C. bengalensis, Cyperus rotundus, Cyperus esculentus and Maricus alternifolius, though scanty, they were difficult-to-control weeds. Summary of weed flora richness showed that Ibadan and Ilora had thirty one (31) weed each. This represented 68.89% of the recorded weed flora composition (45) in all locations. Kishi and Ikenne had ≤ 50% of the overall weed composition recorded. This might be due to cultural practices, weed dominance and agro-ecological variance. High percentage of broad-leaf weeds (≥60%) at all locations, might resulted to keen Kenaf-weed competition due to similarity in morphology and narrows weed control option. Cultural practices, high weed fecundity, short weed life cycle (mostly annual weeds), and wide dispersal corridor in the locations maybe implicated. Weed density and weed dry weight were similar across genotypes in all locations. Ibadan had the highest weed density with the lowest weed dry weight. Ilora and Kishi had comparable weed density. Notwithstanding, highest weed dry weight was recorded in Kishi, while the lowest was recorded in Ilora. This might be due to planting dates, weed types and differences in agro-ecologies.