Standing water is a frequent problem in clay soil. This is because clay does not drain easily. Unfortunately, there is no quick fix for overwatered clay soil. The only way to fix waterlogged clay is to change the character of clay slowly over time. This is accomplished by working amendments such as aggregates, sand and organic material into clay soil. By working both organic fertilizers, such as compost, and aggregates, such as sand and gypsum, into your soil, you change the soil's tilth and increase drainage.
Take soil samples in three or more areas of your garden by first digging a teaspoon-full of soil from the surface of your sampling site. Then dig down 3 inches and dig another teaspoon-full. Place both of these samples into a plastic food storage container.
Label the top of this container with a marker to show which location your sample was dug up in. Repeat this process for each sample location.
Take your soil sample to the local extension office of your nearest land grant college's community and continuing education program to have it analyzed. The soil analysis will include suggestions on what are the best amendments to use, and what quantities to use.
Select amendments for your clay soil based on the suggestions listed in the soil analysis. In general, clay soil will require organic amendments such as peat moss and compost, as well as aggregates such as gypsum and sand. The correct amounts to add to soil will be somewhere between 25 to 50 percent weight by volume.
Break up the soil to a depth of 8 inches using a garden spade.
Spread the amendments over the soil to a depth of 2 inches.
Work the amendments into the soil by turning the soil over with a garden rake.
Repeat steps 6 and 7 a second time.
Water well to distribute amendments throughout soil.