We have problems with our 4 raised beds. We have added lots of organic matter, but the soils still cracks every time the weather gets hot. We water deeply but not too often. Our soil test says our pH is 7.5 and our organic matter is 8.5%.
The problem may be timing. Working wet soils can lead to clods and/or the soil cracking you described. Check the soil moisture before digging, tilling and planting. Grab a handful of soil, gently squeeze, then tap the clump. If it breaks into smaller pieces it is ready to work. If it remains in a clump it is too wet. Wait for the soil to dry before digging in. If the soil is like dust it is too dry to work. Water or wait for rain. Working dry soil can also damage its structure. Though your soil test indicates you have sufficient organic matter you may want to try mulching. Apply a layer of herbicide-free grass clippings, shredded leaves, evergreen needles, straw or marsh hay to the soil surface. The mulch will help reduce weeds, conserve moisture, and reduce problems with soil cracking. These organic mulches can be worked into the soil each fall to help maintain soil organic matter.