The effects on conventional and alternative cropping systems on weed development in continuous crop of maize

A study was conducted in 1996 and 1997, aimed at evaluating the effects that four different cropping systems (conventional, CS; strip cultivation, SCS; organic, OS; and reduced, RS) have on weed development in continuous crops of maize. CS exhibited effective weed control by limiting plant and species numbers to well under the agronomic threshold of tolerance. RS exhibited less satisfactory results when depending on post-emergence weed control only, as did SCS when depending on pre-emergent weed control only. The selectivity of weed control techniques applied in OS (flaming and finger harrowing) seems to be connected with the developmental stage of weeds as well as with the soil moisture content and therefore is not able to ensure adequate weed control. As an overall observation, it does not seem legitimate to consider the analyses from one portion of the cropping technique, no matter how important, separately from its agronomic context. It is probably more important to evaluate whether the choices made in this sector are consistent with those adopted for the entire cultivation of the crop. From this perspective, the greatest problems seem to arise in RS because weed control is carried out later and is not always effective against well-developed adventitious flora.