content in the soil (depth from 0 to 25 cm) of the three crops systems over the 3 years of the experiment. Considerable variations in content in soil were observed in 2004. In 2005, following straw incorporation, a trend showing a higher content in the organic system without straw started to emerge. This trend continued in 2006 with a significantly higher content in the organic system without straw compared to the other soil-bound systems.