Analysis of weed community changes and their determining factors in no-tillage systems

No-tillage systems imply a series of agricultural practices acting together with significant consequences on weed flora adaptations. Absence of tillage produces fundamental habitat changes commonly causing shifts in composition and abundance of weeds. Type of tillage alters light, temperature and moisture conditions sufficiently to modify emergence and establishment of many weeds species. No-tillage systems leads to different herbicide use and reductions in their performance and may result in shifts in species composition. The impact of no-tillage systems on weed communities varies greatly among regions and weed species. While the focus of this review is on the principal agricultural practices and weeds common in the Humid Pampa (Argentina), much especific research is lacking in the country, thus, this paper also draws information from relevant research elsewhere. In most papers reviewed, annual broadleaf weeds are more abundant in no-tillage systems, the exception being wind-disseminated species. Grassy weeds show greater populations in no-till while perennials are not associated to any tillage system. Better knowledge of no-tillage influence on weed flora will contribute to more reliable weed control and adequate environmental management in the region.

Key words: tillage systems, no-till systems, weeds, herbicide performance.