No abstract

Aims: To evaluate and compare the efficiency of candidate herbicides and  increase the latitude of herbicides for pre-emergence weed control in maize. Study Design: Randomized Complete Block Design, with three replicates was used in the study. Place and Duration of the Study: Candidate herbicides were obtained Rainbow Nig. Limited for evaluation. The study was carried out between June – September, 2014 and 2015 at Ibadan (0.7.38N; 003.84E) and Ilora (07.81N; 003.82E) research stations of the Institute of Agricultural Research and Training, Obafemi Awolowo University, Ibadan. Methodology: Weed flora composition was taken with 1sqm quadrat placed randomly before land preparation. Acetochlor 500 g/L, Acetochlor 900 g/L, Metholachlor 720 g and Ametryn 80 WP were applied randomly at three rates of active ingredient (a.i) at maize sowing, while Atrazine (reference), weed-free and weedy check were the control. Agronomic and weed data were taken, analysed and means separated using Duncans Multiple Range Test (DMRT) at p≤ 0.05. Results: Result showed that weed flora composition before land preparation was dominated by annual weeds {broadleaves (80%) and grass (20%)}. At 6 weeks after sowing (WAS), weed flora composition comprised of 8% spiderwort, 8% sedge, 25% grass weeds and 59% broadleaf weed species. Weed flora dynamics after treatments application might have been influenced by types of herbicides, herbicidal activities and previous cultural practices. Herbicides application resultantly increased plant height (50%) and grain yield (46 - 60%) relative to plant height in weedy check at both locations. These might have accrued from minimal weed interference hence, high weed control efficiency (WCE) recorded in herbicides applied (WCE ≥80%) and significant reduction in cumulative weed dry matter of about 80%. Conclusion: Herbicides applied significantly reduced weed growth and enhanced maize grain yield. Notwithstanding, investigation of the benefit cost ratio and the environmental impact assessment of herbicides applied are imperative for sustainability of maize production and agro-ecology.

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.

Purpose. Jute mallow (Corchorus olitorius L.) is a mucilaginous vegetable and fiber crop cultivated in the tropics, where catnip (Nepeta cataria L.) and Mexican sunflower (Tithonia diversifolia L.) are common weeds. Hence, the study investigated the growth, yield, and nutrient level of jute mallow in weed-free, catnip, and Mexican sunflower environments. Methods. The study involved two screen-house experiments in a Completely Randomized Design (CRD) with six replications. The treatments were 0 (control), 2, 4, 6, 8, and 10 weed plants per pot in both experiments. These are 0, 100, 200, 300, 400, and 500 weed count per square meter equivalent, based on the surface area of the pots used. Mexican sunflower and catnip plants interacted with jute plants in the first and second experiments, respectively. Growth parameters of jute mallow were recorded weekly from 5 to 8 weeks after sowing (WAS), and harvesting was done at 8 WAS. The proximate composition of jute was evaluated using standard procedures outlined by AOAC. The data collected were subjected to analysis of variance (ANOVA), and means were separated using Duncan Multiple Range Test (DMRT) at P < 0.05. Results. Catnip and Mexican sunflower negatively impacted the morphological features of jute mallow from 100 plants per square meter upwards. Catnip and Mexican sunflower, at 300 and 100–500 plants per square meter, respectively, reduced the dry weight of jute mallow. The crude protein content of jute mallow was also lessened by Mexican sunflower at some point. Conclusions. The study recommends that the density of catnip and Mexican sunflower plants interacting with jute mallow should be maintained below 100 plants per square meter to prevent yield loss.

Speargrass posed a major constraint to crop producion in some agroecologies in Nigeria.  Hence, the study was conducted to investigate the influence of seasons, rainfall and temperature patterns on speargrass components growth with the view to improve its management. This study was conducted between 2014 and 2016 at Eruwa (7˚32’0˚N, 3˚ 25’0 ˚E, 187m altitude) in Derived savanna (DS) and Kishi (08˚.98’N, 003˚.94’E; 364m altitude) in the southern Guinea savanna (SGS)–northern fringe agroecologies of Nigeria. Twelve months of the year starting from July were randomly assigned to plots in an abandoned speargrass infested farmland, replicated three times and arranged in Randomized Complete Block Design. Monthly temperature, rainfall and speargrass samples (shoot and rhizome) were measured. Results showed that rainfall amount varied across the months in both locations. The highest rainfall was recorded in September (264.20 mm) and hottest month was May, 2016 (28.5oC) in Derived savanna between 2014 and 2016 (Table 1). Kishi had 186 mm rainfall in the wettest months and the hottest months had 28.0 oC within the specified period of the study (Table 2).  Total speargrass total dry weight (STDW) increased with rise in rainfall in both locations. Meanwhile, there were variations in the components (Shoot and rhizome) weight. However, there was decline in speargrass dry matter during the dry months (January to April) in the locations. This might have reflected the effects of moisture deficit.  Notwisthanding, Rhizome:shoot varied  at both locations. Derived savanna (Eruwa) had rhizome:shoot >1.00 in five months throughout the study (5/24), while southern Guinea savanna (Kishi) had rhizome:shoot >1.00 in eleven months (11/24). Speargrass control might be more challenging especially in SGS than DS in the months with higher Rhizome:shoot ratio > 1.00. Derived savanna had more months (19/24 months) with lower rhizome:shoot ratio (< 1.00) than SGS (13/24 months). This might have resulted from more rainy months and better distribution of rainfall in Derived savanna for speargrass shoot growth and the resultant decrease in rhizome:shoot (< 1.00). This is a clue for better translocation of herbicides for season-long speargrass control.