Abstract

Efficient weed control in fallow fields prior to maize planting faces critical challenges due to herbicide resistance and the need to reduce reliance on glyphosate. This study evaluated non-selective and selective herbicide strategies in an on-farm strip-plot validation trial (6 ha) with nested subsampling (n = 6 quadrats per treatment plot). Nine treatments were evaluated, including synthetic herbicides (glyphosate, 2,4-D, paraquat, glufosinate-ammonium, and saflufenacil + clethodim) and commercial bioherbicide (BH02). Weed control efficacy was evaluated using the European Weed Research Society (EWRS) visual rating scale at 14 and 28 days after application (DAA). For perennial grasses (Sorghum halepense and Cynodon dactylon), glyphosate applied at higher rates (4 + 1 L ha^-1 of glyphosate + 2,4-D) achieved 91.0% and 48.3% sustained control at 28 DAA, respectively, whereas contact herbicides permitted severe vegetative regrowth (< 45% control). For annual grasses (Urochloa panicoides and Leptochloa panicea), glyphosate combinations and BH02 provided high control (> 88.8% at 28 DAA), while glufosinate-ammonium alone or with 2,4-D yielded 79.5-92.7% control. For Ipomoea cordatotriloba, glufosinate-ammonium alone (90.5%) and glufosinate + 2,4-D (87.5%) suppressed regrowth at 28 DAA. Product-only economic analysis (2024 commercial rates in MXN ha^-1) showed that BH02 ($3,525.00 ha^-1) was 2.8-fold more expensive than standard glufosinate-ammonium ($1,622.50 ha^-1) and 3.1-fold more expensive than standard glyphosate ($1,125.00 ha^-1), limiting its current commercial adoption. Overall, single postemergence applications do not fully eradicate perennial grasses, but glufosinate-ammonium mixtures represent technically effective alternatives for annual grass and I. cordatotriloba suppression during fallow periods.

This work is licensed under a Creative Commons Attribution 4.0 License.