Long-term changes in soil organic matter under conventional tillage and no-tillage systems in semiarid Morocco

A no-tillage (NT) system was developed in semiarid Morocco to improve the soil fertility and stabilize yield through conservation of water. Results in two long-term trials (4 and 11 years) were able to show the effects of a no-tillage system in increasing total soil organic matter and total nitrogen. Over time, the quality of the NT soil surface was improved compared with that under conventional tillage (CT) with disc harrows. This effect was the result of an increase in soil organic carbon (SOC) and a slight decline in pH. However, over time, nitrogen decreased in both tillage practices, especially in the 0-25 mm layer (from 0.59 to 0.57 t ha(-1) and from 0.44 to 0.42 t ha(-1) under NT and CT, respectively). After 4 years of NT an extra 5.62 t ha(-1) of SOC was sequestered in the 0-25 mm layer, and after 11 years the SOC increased further to 7.21 t ha(-1).