Survey of the floristic composition and the structure of spontaneous vegetation present at green corn cultivated in organic no-tillage system

The control of spontaneous plants is one of the biggest challenges faced by organic no-tillage system (NTS). Thus, the use of cultural practices that help on it becomes relevant. The objective of this research was to evaluate the population density, the level of infestation and fresh and dry weight of spontaneous plants community of the green corn cultivated in organic NTS. The trial was conducted in a randomized block design, with six replications and five treatments, consisting of three soil coverings in the organic NTS and organic and conventional systems using intensive soil tillage without covering. For soil covered treatments was used millet as grass specie and sunn hemp as leguminous specie as well as the intercropping between both species. The green corn (AG 1051 hybrid) was sowed at 1.0 m. between rows and 0.20 m. between plants. Infestation, density and fresh weight and dry weight evaluations of spontaneous plants were performed on the V5 (five developed leaves) stage of corn. The use of single millet straw and intercropped straw provided a reduction of the infestation percentage and absolute spontaneous plants density. Both organic and conventional intensive soil tillage systems without covering showed higher relative density for the specie Galinsoga quadriradiata. The highest relative densities in organic NTS were attributed to Amaranthus spp., C. rotundus and Oxalis spp.. The percentage of infestation by spontaneous plants did not reach the level of economic damage in any of the treatments studied since the average productivity of ears without straw had been within the Brazilian average (9,000 to 15,000 Kg ha-1).