The objective of this research was to evaluateth e effects of the weeds on water consumption and the microclimate in a field of barley (Hordeum vulgare L.), during a drought period. It were evaluated the soil water contents, relative humidity, temperature, water vapor tension, water vapor saturation deficit, water potential, water content in the air at different times (8:30 to 9:00, 11:30 to 12:00, 14:30 to 15:00 and 17:30 to 17:00) and heights (0.0; 0.10; 0.20; 0.30; 0.40; 0.50; 0.60 and 0.70m). The weeds, at high population densities increased the water content in the air, the water vapor tension, the water potential and the relative humidity and decreased the temperature, the saturation déficit and the air movement in the plots. The highest water contents in the soil were observed in highly infested areas, showing that, in this condition, the weeds increased the amount of water available to the crop. In plots with median and low population densities of weeds the water contents in weedy and weed free plots were similar. In plots with low weed populations higher amounts of water were available to the crop in hand weeded plots.
Hordeum vulgare; weed; water; temperature