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Mulching is widely used to control erosion, weed and soil evaporation in water-limited environments. In Southern Italy durum wheat straw could be used as mulch, left on the soil after harvest in June, to increase soil water storage for the horticultural crops sown in August-September.

An experiment was carried out at Foggia during 1998 summer, with the following aim: to verify mulch effect on soil water evaporation and comparing soil evaporation rate in bare (B) and mulched (M) conditions using weighing lysimeters. Three irrigations of 5, 10 and 20 mm were applied either on two lysimeters or in the surrounding one hectare field. 0.5 kg m(-2) of durum wheat straw was applied in the "M" thesis, simulating the disposal residues after harvest; in the "B" thesis only a few stubble (about 0.1 kg m(-2)) was left.

The results indicate the highest evaporation rate of "B" treatment in the first hour after the irrigations or rainfall. Evaporation values of 0.53 mm were found in the "B" treatment with respect to 0.1 mm of the "M" one. In the following hours the evaporation rate became similar and after 18 hours the cumulated soil evaporation were 2.4 and 1.9 mm for "B" and "M" treatments, respectively. The water evaporated in "B" treatment was 73% of the water input, and 60% in the mulched one. In conclusion, a positive effect of straw mulch on soil water conservation was observed in particular for storing water in the upper soil layers.