In a long term trial at the University of Giessen three organic crop rotation systems with and without livestock and four soil tillage treatments (deep plough, 2 x two layer plough and cultivator/rotary harrow) are investigated since 1998. Compared to the other two rotations the stockless rotation without annual green manure showed lower cash crop yields, a negative N-balance and rising weed coverage. The highest cash crop yields were mostly achieved with deep ploughing. Two layer tillage caused N and C accumulation in the upper soil layer (0-15 cm). The weed coverage was highest in these treatments. Especially exclusive tillage with cultivator/rotary harrow resulted in a distinct increase of thistles and high coverage with annual weeds
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