Tine assemblies (100a, 100b, 104) are secured by a single bolt (126) extending diametrically through each tine (120) located in a cavity (112) of a tine plate (110). An outer tine assembly (104) is connected to a sleeve (116) rotatably mounted on independently rotatable shafts (102) to which inner tine assemblies (100a, 100b) are connected. A tine cover (50) removably closes an opening (40) in the top plate (28) and in which weights (70) are removably received over the tine assemblies (100a, 100b, 104). Transport wheels (134) are moveable by pivoting a stop plate (140) to position an upper pivot axis (150a) of an abutment bar (150) ahead of or behind the stop axis (142) and lower pivot axis (150b). A stop (146) positioned on the stop plate (140) without the use of tools adjusts the depth of the tine assemblies (100a, 100b, 104).