Runoff Sediment Quality as a Result of Different Wetting Rate in Soil with Different Land Use.

Detachment and transport during the rain depends of soil surface conditions, especially the initial water content, affected by the velocity needed to reach the rupture-water content of the aggregates. To understand the role of different wetting rate in interrill erosion, was evaluated the total amount and the quality of sediment produced in a soil with different initial wetting rate. Selected sites with corn/soybean crops sequences under No tillage, Conventional (intensive tillage) and Grassland (as a Control), were exposed to artificial rainfall produced with a nozzle-type rain simulator for 60 minutes. The soil was wetted previously with and without the effect of kinetic energy, to simulate the situation of slow and fast wetting rate of the soil surface. A plastic grid was used in soil surface in order to avoid the effect of drop impact. During the first 20 minutes of rain simulation, the runoff and the sediment were collected every minute. After 20 minutes, water and sediment were measured every 5 minutes until the end of the experiment. The collected sediment was sieved in a battery of sieves of 0.5 mm, 0.25 mm, 0.05 mm and smaller of 0.05 mm, oven dried at 60 ºC and weighed.