Herbicides are not allowed in organic farming system which turns the control of weeds plants quite difficult during the cultivation of vegetables. Amongst the weeds, purple nutsedge is specially hard to control due to is aggressiveness. Solarization represents an alternative to soil desinfestation, which consists in covering the soil with a transparent plastic piece and it is capable to show good results regarding purple nutsedge control. An experiment was performed at Embrapa Agrobiologia, aiming to verify the influence of soil preparation and revolving on the efficiency to purple nutsedge control as well as the afterward effect over carrot cultivation. The experiment was set up as a randomized block design with three replications in a factorial 2 x 3 and one additional control: 1) solarized soil prepared (with a grader) and (manual hoe) revolved 30 days after the solarization treatment; 2) solarized soil, prepared and revolved 60 days after the solarization treatment; 3) solarized soil, prepared but not revolved; 4) solarized soil which was only revolved 30 days after the solarization treatment; 5) solarized soil which was only revolved 60 days after the solarization treatment; 6) soil submitted only to solarization; and 7) not solarized soil, not prepared and not revolved (control). Solarization started on January 29, 2002 and lasted 100 days. Solarization reduced 86% of purple nutsedge infestation during carrot cultivation. At the 10 cm depth, soil temperature was higher in the solarization treatments, but at 5 cm depth, solarization was more efficient when associated to soil that has been prepared. The use of hoe to revolve soil did not show any effect. Solarization increased microbial biomass values and soil Ca, Mg and P concentrations. Carrot growth parameters were highly influenced by solarization, resulting in yield increase.
weeds control; plastic cover; Daucus carota; organic horticulture
