Weed management and tillage effect on rainfed maize production in three agro‐ecologies in Mexico

Abstract

Maize (Zea mays L.) is grown in a wide range of agro-ecological environments and production systems across Mexico. Weeds are a major constraint on maize grain yield, but knowledge regarding the best weed management methods is lacking. In many production systems, reducing tillage could lessen land degradation and production costs, but changes in tillage might require changes in weed management. This study evaluated weed dynamics and rainfed maize yield under five weed management treatments (pre-emergence herbicide, post-emergence herbicide, pre-emergence + postemergence herbicide, manual weed control, and no control) and three tillage methods (conventional, minimum and zero tillage) in three agro-ecologically distinct regions of the state of Oaxaca, Mexico, in 2016 and 2017. In the temperate Mixteca region, weeds reduced maize grain yields by as much as 92% and the long-growing season required post-emergence weed control, which gave significantly higher yields. In the hot, humid Papaloapan region, weeds reduced maize yields up to 63% and preemergence weed control resulted in significantly higher yields than treatments with post-emergence control only. In the semi-arid Valles Centrales region, weeds reduced maize yields by as much as 65%, but weed management was not always effective in increasing maize yield or net profitability. The most effective weed management treatments tended to be similar for the three tillage systems at each site, although weed pressure and the potential yield reduction by weeds tended to be higher under zero tillage than minimum or conventional tillage. No single best option for weed management was found across sites or tillage systems. More research, in which non-chemical methods should not be overlooked, is thus needed to determine the most effective weed management methods for the diverse maize production systems across Mexico.

Review of agronomic research on the milpa, the traditional polyculture system of Mesoamerica

“…The use of green manures during this period, instead of letting wild vegetation take over the land, could increase nitrogen and carbon fixation and also reduce weed incidence (Ruiz-Vega and Loaeza-Ramıŕez, 2003;Uribe-Valle and Petit-Aldana, 2007). Fonteyne et al (2022a) evaluated improved fallows in state of Oaxaca, Mexico, where, instead of letting the land fallow, snap bean (Phaseolus dumosus or Phaseolus coccineus) was grown, which increased the yield of the next maize crop and also produced a bean harvest. Alternatively, green manures can be sown as relay crops (before the harvest of the main crop) or in rotation during the winter, if moisture is available.…”

“…In a study in Chiapas, the incidence of pests in maize was double in maize with weeds, although yield was not affected due to the greater presence of predatory insects (Magallanes et al, 2003). In general, with low maize yields, weed control does not necessarily affect maize yield or is simply not economically profitable (Fonteyne et al, 2022a). The negative or beneficial effects of weeds depend on the production system, so weed control must be studied under different conditions.…”

“…The literature cites workloads of 27 to 401 days per hectare per crop cycle for milpa systems, depending on the management intensity and the length of time a field has been under cultivation (Table 1). The higher values mentioned in the literature are the result of attempts to control weeds with high intensity manual control; as previously mentioned, the workload and cost are not justified by the small yield increase (Cuanalo and Uicab-Couoh, 2005;Fonteyne et al, 2022a;Fonteyne et al, 2022b). In the Mixteca Alta, Oaxaca, manual sowing may require more than 50 hours of work Milpa in Yaxcaba on the Yucatan Pensinsula, Mexico.…”