Under direct rays of the sun, soil can heat up to well over 100 degrees to depths of 2 to 4 inches.

One of the best ways to conserve moisture in the soil is to use mulch that insulates the surface from evaporative pressures, resulting from the contact between the hot sun, dry air and dirt.

In addition to breaking the direct contact between the moist soil and dry air, the insulating mulch layer reduces soil heat. Under direct rays of the sun, soil can heat up to well over 100 degrees to depths of 2 to 4 inches. This often results in a 'dead zone' because many plant roots don't function well at such high temperatures.

Research has revealed time and again that 80 percent of root activity is in the upper 8 inches of soil. The right mulch helps keep this area cool enough for roots. Decomposing organic mulches contribute nutrients and provide an environment that encourages micro-organisms to flourish.

Here are a few mulch options.

• Leaves (my personal favorite) – There are two leaf drop seasons to supply foliage for mulch. Live oaks drop leaves in the spring and deciduous trees (pecan, red oak, and others) drop leaves in the fall.
  
  
• Wood chips – Chipped branches and twigs are available from most nurseries, as well as at the Brush Recycling Center, 1800 Bitters Rd.
  
  
• Compost – Unlike mulch, compost consists of completely decomposed organic material. Incorporate 2 to 3 inches of compost into the soil to increase drainage and water-holding capability.

Calvin R. Finch is the project director of regional initiatives and special projects for San Antonio Water System.