Phytosociology of weeds under different soil management systems in field reform of raw sugarcane. = Fitossociologia de plantas daninhas sob diferentes sistemas de manejo de solo em áreas de reforma de cana crua.

The aim of this study was the phytosociological survey of weeds in areas of reform of raw cane, kept fallow after the use of three soil management systems in two regions of São Paulo. The study was conducted during 2007/08 crop year, in commercial production in the municipalities of Novais and Guaira. The last harvest of sugarcane was done in the first fortnight of July 2007. We used randomized block design, the treatments consisted of three soil tillage systems: conventional tillage, minimum tillage and no tillage. After treatments of tillage plots were maintained in a fallow period of 150 days. We carried out sampling in each plot by doing the identification, counting and collecting all the shoots of the weeds present. The data were interpreted statistically by ANOVA and Tukey’s test, then calculated the phytosociological index. No-tillage gave lower dry matter and fewer weeds than the other soil management systems in two growing regions. The Guaira region had a higher weed infestation that the region of Novais, where the species that stood out, presenting high IVR in all types of management was the Cyperus rotundus L. The importance of this species decreased with the use of more conservation managements. The similarity between tillage and conventional tillage was lower in both regions.