Peach trees struggle when grown in soils that have poor drainage such as those with a heavy clay component. With significant soil amendment at planting time, top-dressing each year thereafter, along with careful irrigation practices, you can grow peaches in soil with a considerable natural clay content. Choose a high-ground location where water drains away from the soil and not where it pools, to aid in maintaining a well-drained soil.
Calculate the amount of organic soil amendments needed by measuring the square footage of your planting area. You will need to use roughly 20 cubic feet of organic matter to cover 100 square feet of planting area. For only light clay soils, you can scale back on the amount of organic matter accordingly, but more organic matter will not hurt but only help the tree.
Amend your clay soil with the proper amount in roughly equal proportions of sharp sand or coarse builder's sand to aid drainage, and well-aged manure, peat and good-quality compost to create loam and build soil fertility. Dig in or mechanically till in the soil amendments to a depth of at least 3 feet.
Top-dress the area under the peach tree each year with several pounds of good-quality compost and well-aged manure, scratching the amendments into the soil surface with a rake and watering in well. Annual compost application can play the role of mulch or you can add an inch or so of shredded bark or coca bean hulls over the compost and manure to further protect and feed the soil.
Water your peach tree deeply once a week to every 12 days during the growing season as needed to keep the soil evenly moist but not soaking wet and never completely dry when reaching 2 to 3 inches down into the soil.