Effect Of Chemical Weed Control And Intra-Row Spacing On The Growth And Yield Of Popcorn ( Zea Mays L. Var. Everta) In The Northern Guinea Savanna Of Nigeria
Field trials were conducted at the Institute for Agricultural Research Farm, Samaru (11° 11 N.07° 38’E) in the northern Guinea Savanna Ecological Zone of Nigeria to study the effect of chemical weed control and intra-row spacing on the growth and yield of popcorn (Zea. mays L. Var. everta) in 1995 and 1996 wet seasons. The treatments tested consisted of eight pre-mergence herbicides supplemented with one hoe-weeding at 7 weeks after sowing (WAS). These were compared with three hoeweedings at 3, 6 and 9 WAS and a weedy check. These were tested under spacings of 15, 30 and 45cm. The treatments were laid out in a split plot design with three replications . In both years of experimentation, the use of herbicides (except metolachlor + metobromuron at 1.0 + 1.0kg a.i./ha) and hoe-weeding consistently resulted in significantly lower weed cover score, weed dry matter production and higher popcorn grain yield than the weedy check. However, the most promising herbicide treatments were pro-emergence app]ication of metolachlor at 2.0 kg a. i./ha and its combination with atrazine at 1.0 + 1.0 kg a.i./ha and 1.2 5 + 1.25 kg a.i./ha each followed by supplementary hoe-weeding at 7 WAS. These treatments resulted in effective weed control and higher popcorn grain yields than other herbicide treatments. In both years, crop planted at intra-row spacing of 15cm on 75 cm ridges resulted in significantly lower weed cover score than those of 30 and 45cm spacings at 6 and 9 WAS. Crop vigour and number of leaves per plant at 6 WAS, plant height and leaf area index at 6 and 9 WAS, total dry matter production per plant at harvest, cob weight, number of cobs per plot, cob yield and grain yield (kg/ha) in both years also increased with decrease in intra-row spacing. The Interaction between weed control treatments and intra-row spacing on weed cover score at 9 WAS, weed dry matter production, cob yield and grain yield in both years were significant. In this, interaction mixture of metolachlor plus atrazine at 1.0 + 1.0 kg a.i./ha applied pre-emergonce under the intra-row spacing of 30cm combined effective weed control with high pop-corn grain yield comparable to the hoe-weeded control. Unrestricted weed growth throughout the crop life cycle resulted in 83.8 and 72.9% reduction in popcorn grain yield compared to the maximum obtained in each trial in 1995 and 1996 wet. seasons, respectively.