Dense, compacted clay soils prevent appropriate water drainage. Poor drainage results in flooding and poor plant health. Improving the condition of clay soil does not have to be expensive, but it does take time. Cheap fixes for clay soil are not quick, but they will work over time.
Plant a cover crop to protect soil in between plantings of desired crops. Cover crops can be winter crops or summer crops. To improve the structure of clay soil, plant crops that have a long taproot to break up the clay. Bell beans, winter rye, daikon and mustard are examples of winter cover crops. The seeds are inexpensive and cover large areas. Plant the seeds in the fall for growth through the winter. Till the crop into the soil in spring to provide organic material needed for improving the soil's structure.
Or plant alfalfa or green clover as a cheap fix for clay soil. Alfalfa has a taproot that reaches deep into the soil and break up extremely compacted soils. The network of roots from green clover also breaks up clay. Alfalfa and green clover act as green manure. Plant them as a summer crop and till into the soil in the fall.
Till the soil to a depth of 6 inches. Remove all rocks and break up large chunks of soil. Spread a 4-inch layer of coarse sand over the clay soil. Lightly till the sand into the soil. Spread a layer of coarse compost on top. Till the compost into the soil. Add a 4-inch layer of manure to the soil and thoroughly mix it into the top 12 inches of soil. Measure the area to determine how much material to buy by multiplying the width by the length. When fresh manure is used, allow it to compost for four months before incorporating it into soil. Make cheap coarse compost by thoroughly mixing well-rotted manure with composted leaves, straw or wood chips. Buy materials in bulk. Bulk products are cheaper than individual bags. The packaging will indicate how many square feet the material covers.
Add earthworms to improve soil structure. Worms create tunnels and break up clay soil so oxygen and moisture readily move through the soil. The oxygen assists bacteria in breaking down organic materials used to amend clay soil. Worm castings improve soil structure and help it fight off diseases. Incorporating generous amount of rich organic matter into the soil attracts earthworms. Contact the county extension office for a list of places that sell earthworms.