Evaluation of pre-emergence herbicides and hoe weeding for weed control in Roselle (<i>Hibiscussabdariffa .L.</i>) in Northern Guinea Savanna of Nigeria

Abstract

Two field experiments were conducted during the raining seasons of 2011 and 2012 at the Institute for Agricultural Research, Samaru to evaluate the influences of pre-emergence herbicides and hoe-weeding on growth and yield of roselle.The treatments were five herbicides; metolachlor, butachlor, oxadiazon, pendimethalin each at two rates1.5 and 2.0kg a.i/ha, diuron at 2.0 and 2.5 kg a.i/ha, (HW) at 4,(HW) 3 and 6 and (HW) 3, 6 and 9 weeks after sowing (WAS) and a weedy check.The experiment was laid out in a randomized
complete block design and replicated three times to give a total of fourteen treatments. Data were collected on weed dry matter, Weed control index at 9 and 12WAS and herbicide efficiency index at 12WAS.Others were crop injury at 2WAS, plant height, number of leaves and number of primary branches/plant at 9 and 12WAS. Number of calyx, weight of calyx/plant, calyx yield and combined yield at harvest. Diuron at 2.5kg a.i /hahad significantly lower weed dry matter and highest weed control efficiency than the other herbicide treatments and was comparable to two hoe-weeding at 3and 6 WAS at 9 and 12 WAS. Highest crop injury was obtained by diuron at 2.5kg a.i /ha in 2011. Among the herbicides, pendimethalin, metolachlor and butachlor each at 1.5 and 2.0 kg a.i /ha were consistent in combining good weed control with higher crop growth and yield attributes. Pendimethalin at 2.0kg a.i /ha gave significantlyhigher herbicide efficiency, lower weed dry matter and weed control index. Also had more number of calyx, higher calyx weight and calyx yield in each year of trial and combined compared to other herbicide treatments. In conclusion, for effective weed control and higher calyx yield, pendimethalin at 1.5 or 2.0kg a.i /ha is recommended as an alternative two hoe-weeding at 3 and 6WAS and therefore could be considered by the roselle farmers in this region for effective weed control.

Keywords: Herbicides, roselle, weeds, WCE, HEI