Effects of tillage and cropping systems on the structural stability and soil organic matter in semi-arid areas of Morocco

Soil degradation is becoming the major problem of Moroccan soils in semiarid areas. This deterioration is due to poor soil management through recurring tillage practices that cause a decline in soil organic matter and degradation of their structural state. This study aims to characterize the impact of tillage, residue management and cropping systems on the aggregate stability and the accumulation of organic matter in a Calcixeroll soil. Three tillage treatments were compared: conventional off-set disking, no-tillage system with two levels of residue: NT100 = full surface residue cover and NT50 = half surface residue cover, along with three rotations: continuous wheat, fallow?wheat and fallow?wheat?barley. The results showed that compared with conventional tillage, no-tillage allows an improvement of aggregation and organic matter content of the sampled horizons (0-5, 5-10 and 10-15 cm). The total coverage of plots by 100% of mulch residues (NT100) has helped to increase the level of organic matter in all soil fractions (aggregates andlt;0.5 mm andandgt; 8 mm). It was found also that the continuous wheat rotation has improved the structural aspects of the soil and allowed the accumulation of organic matter compared with rotations with fallow. In conclusion, soil quality (stability and organic matter) was improved in no-tillage condition, especially with a maximum contribution of surface residue (NT100).