What type of soil do you have: heavy clay, humus? Do you have a hard pan several feet below your soil? A hard pan does not necessarily mean a rock layer. It could be a compacted organic soil layer. If so, consider liquid aeration. That is a combination of powerful surfactants to break water tension, allowing the water to penetrate the soil. If you have clay soils, humus in combination with surfactants will provide aggregation, allowing the soil to breath. I recommend Super Aerate, because it has the highest concentration of surfactants that I know of.