Kenaf Morpho-physiological Variations and Response to Weed Pressure in Derived Savanna Agro-ecology of Nigeria

Kenaf response to weed pressure depends on variations in morpho-physiological traits of genotypes. A study was conducted in Ibadan (7°38’ N 3°84’ E) Nigeria in the wet seasons of 2014 and 2015 to determine the response of kenaf genotypes to weed pressure. Twelve kenaf genotypes were planted in a conventionally prepared seedbed at 50 × 20 cm, in 5 x 5 m plot and arranged in an RCBD, replicated thrice. Initial weed flora composition revealed that Panicum maximum, Tithonia diversifolia, Mithracarpus viridis, Commelina spp, Aspilia africana, Tridax procumbens and Pennisetum purpureum were predominant in the experimental site. Kenaf plant height varied significantly and ranged from 30.53 cm to 59.73 cm and 60.67 to 76.80 cm at 6 weeks after sowing (WAS) in 2014 and 2015 respectively. Variation in plant height at 10 WAS did not follow the previous growth patterns in both years of the study. Stem girth at 10 WAS ranged from 1.26 cm (V1-400-2) to 1.47 cm (A-60-282) in 2014. In subsequent year, Tianung had 1.47 cm stem girth as the thinnest, while Cuba 108 had the thickest stem (1.70 cm). Ifeken 400 (56.90 cm) and Cuba 108 (53.57 cm) had the broadest canopy width in 2014 and 2015 respectively, while A2-60-28 (44.85 cm) and V1-400-2 (41.33 cm) had narrowest canopy width in 2014 and 2015 respectively. Genotypes had comparable fibre yield, possibly due to catch-up growth from 8 to 10 WAS. Ifeken 400 (480 kg/ha) and Ifeken DI400 (550 kg/ha) had the highest seed yield in 2014 and 2015 respectively. These were similar with seed yield in other genotypes except V1-400-2 (310 kg/ha) in 2014 and AC-313 (350 kg/ha) in 2015. However, seed yield reduction across genotypes ranged from 55 – 74%, with an average of 68% in both years when compared with the seed yield potentials of genotypes. Evidently, prolonged weed competition might have accounted for the seed yield deficit recorded in the study. Invariably, pre-emergence weed control only may not suffice for weed pressure in kenaf plot when seed production is of interest to the farmers. There was significant weed interference in plots sown to kenaf genotypes with low plant height and narrow canopy width. Consequently, high weed dry weight in V1-400-2 (66.39 g/m2; 89.39 g/m2) might be responsible for seed yield penalty in both years of the study. Whereas, Ifeken DI400 had the least weed dry weight (25.93 g/m2; 26.92 g/m2) and comparable seed yield with the maximum in both years of the study. Genotypic variations in morphological and physiological traits might be responsible for responses to weed interference and crop performance. Early expression of weed suppressive traits evidently influenced genotypes-weed interaction.