1. Introduction
Conservation tillage has been defined as a tillage and
planting system that retains at least 30% of cover crop
residues on the soil surface after planting operation is
completed. Erosion is reduced by at least 50% in these
soils as compared to bare soils (McCarthy et al., 1999).
Retaining crop residues on the soil surface provides a
source of plant nutrients, improves organic matter level
in the soil, and increases soil water content by reducing
evaporation and increasing infiltration rate (Chastin
et al., 1995). Conservation tillage systems not only
reduce erosion and improve the soil environment for
crop growth, but also conserve energy and decrease the
labor cost of farming (Triplett and Van Doren, 1977).