Tilling or plowing (15–20 cm)

Why till

Grass roots grow through loose, crumbly soil and stop at hard layers. Breaking up the top 15–20 cm (6–8 in) lets roots, air and water down, and gives you a chance to mix in any compost, sand or lime the soil needs.

When the soil is right

Squeeze a handful. If it forms a sticky ball, it is too wet: tilling will smear it into clods that set like bricks. If it is dust, it is too dry. The right moment is when it crumbles in your hand.

How

• Use a rotary tiller (rotavator) on small and medium plots, or have a larger area plowed and harrowed.
• Make one pass, then a second at right angles.
• Add amendments before the second pass: well-rotted compost on poor soil, coarse sand on heavy clay, lime only if a pH test says so.
• Do not overwork it. Too many passes pulverize the structure and the surface crusts after the first rain.

Afterwards

Pick out stones and roots the tiller brings up, then let the soil settle for a week or two before leveling. A freshly tilled bed is fluffy and will sink unevenly if you sow straight away.