Increasing Array of Herbicides for Post-emergence Weed Control and Seed Yield in Maize (Zea mays Linn)

Abstract

Study was conducted at the Institute of Agricultural research and Training (IAR&T) Ilora (Derived savanna agro-ecology) substation in the rainy seasons of 2014 and 2015, to appraise herbicides for post-emergence weed control and increase array of herbicides for weed control in maize. Weed samples were taken from a three-year fallow field before land preparation. Herbicides under evaluation were assigned to 3 x 3 plots at different rates. These were arranged in randomized complete block design (RCBD) with three replicates. The results showed that initial weed flora richness were 22% and 78% grass and broad-leaved weeds respectively. These were found in five (5) plant families. All the weeds sampled were annuals. Narrow annual weed spectrum, described continuous cropping activities in the location. Herbicides improved plant height by 36 to 50% compared to weed infested maize plants. Though phyto-toxicity was evident at three and twenty-one  days after treatment (DAT), ranging from 1/10 to 3.79/10 and 2/5 and 3.67/10 correspondingly when visually rated (0 – 10 scale). Notwithstanding, herbicides gave impressive weed control rate (WCR) at 21 DAT (6.7/10  - 8.7/10), with evidence of superior weed control efficiency (WCE >80%) at harvest across herbicide treated plots relative to weedy control plots. 2,4-D DMA (0.86 kg ai/ha), Fluroxypyr methyl (0.40 ai kg/ha), 2,4-D + Dicamba (0.68 + 0.24 kg ai/ha) and 2,4-D DMA (2.58 kg ai/ha) had <30% relative yield loss (RYL%) with comparable seed yield compared to the highest recorded in weed-free plot (13.29 t/ha). Plant height at 8 WAS (weeks after sowing) had significant inverse relationship with weediness at 5 WAS and weed dry weight at harvest (- 0.62). Consequently, early weed control is essential for maize performance. On the other hand, plant height enhanced weed control efficiency at harvest (0.62). Tall plants have tendency to reduce relative yield loss (RYL %) as they were inversely related 1 (- 0.42). Comparable WCE% (83 -99%) in herbicide treated plots reduced weed growth by about 88%. Hence, lower rate of herbicides with <30% phyto-toxicity level should be considered to increase array of herbicides for post-emergence weed control, sustainable maize production and environmental friendliness.