The effects of surface mulches from corn and wheat crop residues on the direct soil water evaporation stages were analyzed for two soils of different textural classes. The treatments consisted of three rates of crop residues, 0, 50 and 100% of the dry matter and three water evaporative demands. The bare soil water evaporation presented distinct behavior for the three tested water evaporative demands. For the water evaporative demand of nearly 3 mm d-1, the treatment with bare soil stayed in the first stage of evaporation rate, at least for the period of 21 days of the experiment. The concept U established by Ritchie (1972) to define the end of the first water evaporation stage, was not observed for the water evaporative demands of 5.2 and 3.0 mm d-1. For these demands, the soil stayed in the first evaporation stage during the data collection period of 21 days. For the residual rate of 100% of dry matter and for the corn and wheat cultivations, the evaporative demand had a modest influence in reducing the soil water evaporation, which on average varied 28% of the evaporation occurred in the treatment with bare soil, having significant difference among the residual rates, but did not occur differences between the two soil classes, for the water depth evaporated in 21 days.
evaporation; residues; evaporative demands; evaporation stage
