Evaporation of soil water based on the quantity and uniformity of crop waste distribution in soil superficies

Plant residues influence the energy balance and water vapor flux on the soil surface. The aim of this research was to quantify the effect of the amounts and distribution of crop mulching on evaporation of soil water. The study was carried out at the Instituto Agronomico do Parana, located in Londrina City, State of Parana, Brazil. In experiment 1,  soil water evaporation was determined according to the quantity of soybean and wheat residues applied (0, 2, 4 and 6 t ha-1); while in experiment 2,  soil water evaporation was determined based on the distribution of 4 t ha-1 residue of soybean and wheat, which was applied in 33, 66 and 100% as soil cover. Eight weighing lysimeters were used with two replications, and denominated cycles for each experiment period. The results showed that compared to bare soil, reduced evaporation at the end of the evaluations were 17% for  2 t ha-1, 28% with 4 t ha-1 and 25% for 6 t ha-1 of residues of soybeans, in the first cycle during winter. During spring cycle, evaporation reductions in cycle 1 were 10, 12 and 23% for 2, 4, and 6 t ha-1, respectively. Soil water evaporation decreased, compared to the bare soil, as soon as soybean residues rate increased. This showed the largest reduction (29 to 33%) when the residues were distributed uniformly over the lysimeters. Key words: Lysimeter, water balance, soil moisture.