Lawns and gardens are more difficult to establish on clay soils than on loamy soils. However, competent gardeners, landscapers and farmers are invariably successful when working with clay soils. The keys are:

1) Organic Matter- Applying large amounts of organic matter and mixing it in the top   8-12 in.(15–30) cm of soil is the key to managing clay soils. It would be difficult for you to apply too much organic matter. At least 5 cm of material should be applied and incorporated to markedly improve a clay soil.

Well-rotted animal manure, sawdust (do not use cedar), composted garden and kitchen refuse, peat moss, dried sea weed and spent mushroom compost are common organic amendments available to most gardeners. Medium to coarse sand combined with organic soil amendments can help open up some of the compacting elements of clay soil, but a substantial amount of sand must be used for this to be affective. Lava Sand is made from ground scoria, a red lava. Because of lava’s porous nature, this sand is a great additive for clay soils

2) Drainage -  Surface puddles after a heavy rain do not necessarily mean your clay soil has poor drainage, but a consistently wet soil into the late spring means that you have a high water table that is restricting water movement on your property. A properly graded soil surface that will enable surface water from heavy rains to run off the lawn will improve the drainage situation.

3) Prevent heavy use of lawn during wet weather - When wet clay soils compact easily and to avoid long term damage or costly renovation reduce the amount of traffic or playing on lawns.

4) Proper fertilization - If sawdust, peat, or seaweed are used, extra nitrogen must be applied to prevent poor growth due to a nitrogen deficiency. Apply at a rate of 0.7 kg 34-0-0 or 0.5 kg 46-0-0 per cubic meter of organic material (1.5 lb 34-0-0 or 1.0 lb. 46-0-0 per cubic yard). Apply lime at a rate of 20 kg per 50 m2 (50 pounds per 500 square feet) and thoroughly incorporate with the organic material.

5) Low Irrigation Rates - Most garden sprinklers apply water well in excess of the amount that clay soils can absorb. This results in surface ponding, soil structure breakdown, reduced air porosity of the soil which will hinder the growth of most seedlings. Add water to a clay soil at less than 0.5 cm/hour to allow absorption. Sprinklers heads or irrigation kits such as  Drip Irrigation for Dummies Kit can be purchased through most garden shops that are specially designed for low rates of application.

6) Proper Moisture Content - Clay soils must have the proper moisture content before worked; if the soil is too dry, roto-tilling will be an impossible task due to the concrete like hardness of the soil. If the soil is too wet, the sticky, plastic nature of clay will make working very difficult.

Gentle irrigation of dried-out clay (12 hours at ½ in (0.25) cm per hour followed by a 2 day rest) or surface drainage of water-soaked clay followed by a period of dry weather would provide the optimum moisture required for tillage.