It seems that no matter the problem we face in our gardens, the answer — or at least a part of the answer — frequently includes compost. This is certainly true in xeriscape gardening, the process of using minimal moisture effectively. Soil conditioning is one of the seven principles of xeriscaping. Soil that retains moisture while still allowing moisture to move through it is the goal. While there are many amendments that can be added to particular kinds of soil — clay or coarse — to help them conduct and retain moisture properly, the first and best step (because it also adds valuable microorganisms to the soil) is composting.
Gayle Weinstein’s excellent text Xericscape Handbook: A How-To Guide to Natural, Resource-Wise Gardening does a good job of explaining how water moves (and stays) in soil. Water, filtering from top to bottom, fills the spaces around each soil particle. Gravity pulls the water through the soil, but capillary action holds some of the water near the surface. When gravity draws some of the water away from plant roots through the soil and the capillary water is lost, either through evaporation or plant uptake, what’s left is called hygroscopic water, the water absorbed by the soil particles and slowly given up as capillary water between the soil particle spaces vanishes. (more…)