Weed control efficacy of hoe weeding and commercially formulated mixture of metolachlor + prometryn herbicide under maize production in soil amended with biochar

Successful cultivation of maize depends largely on efficient weed control, adequate supply of essential nutrients and sufficient soil moisture. Screenhouse and field trials were conducted at the Teaching and Research Farm of the Federal University of Agriculture, Abeokuta, Nigeria during the early and late cropping season of 2013 to evaluate effects of biochar integrated with manual weeding and pre-emergence herbicides on weed control efficiency and productivity of maize. The screenhouse trial was a 6 × 5 factorial experiment fitted into Completely Randomized Design in three replicates. The two factors were biochar: 0, 2, 4, 6, 8 and 10 t ha⁻¹ and weed control methods: weedy check, hoe weeding at 6 Weeks After Sowing (WAS), hoe weeding at 3, 6, and 9 WAS, pre-emergence herbicide application (Codal Gold) at 1.0 and 2.0 kg a.i./ha⁻¹. The field trial was laid out in split-plot arrangement fitted into Randomized Complete Block Design with three replicates. The three main treatments plots on the field consisted of the optimum rates of biochar obtained in the screenhouse (10 t ha⁻¹) compared with 20 t ha⁻¹ and 0 t ha⁻¹ which served as the control. The sub-plots treatments consisted of weed control methods used in the screen house experiment. Data were collected on grain yield and weed dry matter. The result showed that biochar at 10 and 20 t ha⁻¹ in the screenhouse and field trials, respectively, resulted in significantly (P < 0.05) higher grain yield compared with other rates tested. Highest grain yield was obtained in pots hoe weeded thrice at 3, 6 and 9 WAS. Whereas similar grain yield was recorded in plot weeded once at 6 WAS and that hoe weeded at 3, 6 and 9 WAS in the field experiment. Biochar application of 20 t ha⁻¹ gave optimum maize yield. Among the weed control treatments manual weeding either at 6 WAS or at 3, 6 and 9 WAS recorded the highest grain yields. Therefore, incorporation of biochar with either preemergence herbicide or manual hoe weeding would enhance the growth and yield of maize.