Weeds in Milpa: Richness,Perception,and Their Traditional Uses and Knowledge

Abstract

Weeds growing in Mesoamerican traditional maizefields, or milpas, represent a reserve of genetic resources and knowledge. To explore tendencies on the influence of natural and cultural attributes on milpa weeds and their knowledge, we studied species richness, perception, and use of adventitious plants in milpas across an agroclimatic and cultural gradient in Altiplano, Rioverde, and Huasteca milpas in the state of San Luis Potosi, México. The study involved semi-structured interviews and recording weed presence in milpas. Farmers from Huasteca, who often used herbicides and fertilizers in milpas, had a negative perception of weeds and their milpas registered a lower species richness. By contrast, farmers from Altiplano, who mostly managed milpas without industrial inputs, perceived weeds in an ambivalent manner (neither positive nor negative) and their milpas registered the highest species richness. Thus, an association between weed richness and management practices was identified. Farmers collectively recognized 67% of the species present in milpas, and from the total number of species registered, interviewees mentioned specific medicinal uses of nine species that have not been scientifically studied although those species have other scientifically known uses. Forage was the most common use of weeds in milpas from Altiplano and Rioverde, food in Rioverde, and agronomic as soil fertilizer in Huasteca. Milpa farmers collectively still preserve knowledge about weeds that showed differences depending on the uses and region. Promoting milpa agroecosystem ethnobiological knowledge is important to maintain sustainable practices and biodiversity.

In Mexico, many farmers still grow corn using an age-old method called milpa, where corn is planted alongside other crops and where weeds are allowed to grow to be harvested for different uses. This research explored how the environment and farming practices affect the types of weeds that grow in milpas, how farmers view them, and how they use them. Farmers that commonly use herbicides and fertilizers, tended to see weeds as a problem, and fewer weed species were found in their fields, while farmers using fewer or no industrial chemicals had a more neutral attitude toward weeds and their fields had the highest number of weed species. Milpa farmers across a natural gradient and from diverse ethnic groups identified about two-thirds of all the weed species growing in their fields. Different regions have different practices and views on weeds, but overall, milpa farmers continue to pass down valuable knowledge about the plants around them. This study shows that traditional farming systems like milpas are not just about growing crops, they are also important for preserving biodiversity and traditional knowledge.