Impact of Nitrogen Levels and Weed Control Methods on Growth and Yield of Okra (Abelmoschus esculentus (L.) Moench) in the Nigerian Forest-Savanna Transition Zone

Abstract

Aim: To evaluate the effect of nitrogen levels and weed control methods on the growth and yield of okra. Study Design: Treatments were laid out in a split-plot design. Place and Duration of Study: Field trials were conducted at the Teaching and Research Farm of the Federal University of Agriculture, Abeokuta, Nigeria in the early and late wet seasons of 2015. Methodology: The main plot treatments comprised of three nitrogen (N) levels (0, 60 and 90 kg N/ha), while the sub-plot treatments were made up of seven weed control methods (probaben® [metolachlor 20%  w/v + prometryn 20% w/v] at 2 kg a.i/ha; probaben® at 2 kg a.i/ha followed by supplementary hoe weeding (SHW) at 6 weeks after sowing [WAS]; butachlor [50% w/v]  at 2.0 kg a.i/ha; butachlor at 2.0 kg a.i/ha followed by SHW at 6 WAS; 2 hoe weedings at 3 and 6 WAS; 3 hoe weedings at 3, 6 and 9 WAS; and weedy check).  Results: Unchecked weed growth throughout the crop life cycle resulted in 51 and 59% reduction in potential okra fruit yield in the early and late wet seasons, respectively. Application of N at 90 kg/ha compared to lower rates, increased weed density and weed dry matter production in both seasons. N application at 90 kg/ha resulted in significant increase in growth and fruit yield of okra. All weed control methods resulted in significant reduction in weed growth, and subsequently increased okra fruit yield. The most effective weed control methods were pre-emergence application of probaben® and butachlor at 2.0 kg a.i/ha each followed by SHW at 6 WAS. Conclusion: Results suggest that farmers can reduce the burden of hoe weeding and cut down on labour input with the use of pre-emergence herbicides for weed control in okra production, and increase okra yield with application of N into the low fertile soils of the forest-savanna transition zones.