Nitrogen and weed management in transplanted tomato in the Nigerian forest-savanna transition zone

Weed infestation and inherent low soil fertility are among primary reasons for low yields of tomato in Nigeria. Field trials were carried out during the wet season of 2015 and 2016 to evaluate yield response of tomato to nitrogen (N) application and weed control methods in the forest-savanna transition zone of Abeokuta, Nigeria. Positive relationship exists between growth of weed species and increase in N application. Across the years of study, increase in N up to 90 kg/ha increased weed density by 11-25%, however, the increased N gave the transplanted tomato competitive advantage and thus enhanced weed smothering. Pre-transplant application of butachlor (50% w/v) or probaben® (metolachlor 20% w/v + prometryn 20% w/v) each at 2.0 kg a.i/ha followed by supplementary hoe weeding at 6 weeks after transplanting (WAT) significantly reduced weed density by at least 15% and increased fruit yield of tomato by at least 32%, compared to use of the pre-transplant herbicides alone, across both years of study. The greatest tomato fruit yield of 12.2 t/ha was obtained with pre-transplant application of butachlor at 2.0 kg a.i/ha followed by supplementary hoe weeding at 6 WAT, averaged for both years. In general, this study suggests that increased application of N up to 90 kg/ha, and complementary weed control by pre-transplant herbicide and hoe weeding at 6 WAT would improve yield of tomato in the forest-savanna transition zone of Nigeria.