Evidence of synergy with stacked' intrarow cultivation tools

Intrarow cultivation efficacy is often low and highly variable. As the mechanisms affecting weed mortality likely vary by tool, several companies have developed cultivators with the ability to use several different intrarow tools at once. We evaluated the potential for such stacking' of cultivation tools to increase efficacy. We used different sequences of torsion weeders, finger weeders and row harrows in a test crop of maize with surrogate weeds, Sinapis alba and Panicum miliaceum. Most tool combinations resulted in an additive increase in efficacy compared with the individual tools, but the combination of torsion-finger-row harrow demonstrated a synergistic increase in efficacy. In separate experiments, forward speed, soil moisture and weed size were negatively correlated with efficacy, but the torsion-finger-row harrow combination continued to demonstrate a synergistic increase in efficacy compared with the individual tools in 7 of 11 cases. The drawback was high crop mortality (16.0 +/- 1.16%); further mechanistic research is needed to reduce crop mortality while maintaining high mean efficacy, through tool design, adjustment and cultural factors.