Carrier Volume is More Likely to Impact Trifluralin Efficiency than Crop Residue

PRE herbicides are generally less effective in conservation farming systems because of high levels of crop residue. However, performance can be improved if the herbicides are applied with a high carrier volume. This research investigated the interaction of carrier volume and row spacing or height of crop residue on the control of rigid ryegrass with trifluralin, at Cunderdin and Wongan Hills Western Australia. To create plots with varying residue row spacing in 2011, wheat was seeded in 2010 using a narrow row spacing (25 or 22 cm at Cunderdin and Wongan Hills), wide spacing (50 or 44 cm), or not planted to wheat. Narrow or wide row spacing or no crop plots had an average residue biomass of 4480, 3560, and 2430 kg ha−1 at Cunderdin and 1690, 1910, and 1030 kg ha−1 at Wongan Hills. To vary residue height, the wheat was harvested to produce tall, medium, or short crop residue (22, 13, and 5 cm at Cunderdin and 27, 22, and 17 cm at Wongan Hills). Rigid ryegrass seeds were broadcast onto each site in 2011 and trifluralin was sprayed using 50, 75, or 100 L ha−1 carrier volume (directly prior to seeding). Increased carrier volume increased spray coverage at both sites (average cover of 9, 15, and 26% at 50, 75, and 100 L ha−1), leading to improved control of rigid ryegrass (68, 75, and 82% control at Cunderdin and 23, 41, and 68% control at Wongan Hills). Reduced crop residue height or increased row spacing led to reduced rigid ryegrass density at Cunderdin but had no impact at Wongan Hills. Therefore, carrier volume has a more consistent impact on the performance of trifluralin than crop residue row spacing or height. Nomenclature: Trifluralin; rigid ryegrass, Lolium rigidum Gaudin; wheat, Triticum aestivum L. Los herbicidas PRE son generalmente menos efectivos en sistemas de producción con conservación de suelos debido al alto nivel de residuos de cultivo. Sin embargo, se puede mejorar el desempeño de los herbicidas si estos son aplicados usando altos volúmenes. Esta investigación estudió la interacción entre el volumen de aplicación y la distancia entre hileras y la altura del residuo del cultivo sobre el control de Lolium rigidum con trifluralin, en Cunderdin y Wongan Hills en el oeste de Australia. Para crear las parcelas con diferentes distancias entre hileras de residuos en 2011, se sembró trigo en 2010 usando una distancia entre hileras corta (25 ó 22 cm a Cunderdin y Wongan Hills), una distancia larga (50 ó 44 cm), o no se sembró trigo del todo. Las dis