Our precious soil is much more than the mineral or dirt component which is so visible to us and may dirty our hands when we work it.  A good soil is only around 45% mineral material which has eroded from a rock base.  There is also air, water, and organic material (dead and alive) to add to the complex which allows for the growing of plants on land.

Soil water (30% of soil) is possibly the most important constituent of soil because it is so active.  It is present in three forms:  hygroscopic, capillary, and gravitational.  Hygroscopic water is tightly held by soil particles.  In the space between the particles of soil is found the capillary water.

The overwhelming quantity is the gravitational fraction which floods the soil during rainfall and is pulled by gravity to depths beyond the reach of plants in a short time.  Other water near the surface of the soil is pulled back into the atmosphere by evaporation.  Therefore, it is a real battle to maintain sufficient water in the soil to support plant life and in the end the lives of us humans.

Water has certain characteristics which allow for plants to grow and survive.  There is its ability to act as a very good solvent that takes up small amounts of mineral material from that fraction of the soil as well as oxygen and carbon dioxide gases from the soil air.  They are then transferred to plants by the well-known process of osmosis.

Water also has good characteristics for cohesion and adhesion which help it to cling to the mineral soil particles and is a great aid in the transfer of water upward in plants.  It has a good heat coefficient which helps to control the soil temperature.  It is colorless and thus does not impede light.

Most all of the water used by plants is absorbed through the root hairs and then moves upward through the phloem tissue of the stems and branches to the leaves.  There a portion is used in photosynthesis to manufacture simple sugar and beyond to cellulose, protein, etc.  Water is a plant’s primary food.

Another greater portion is expired back into the atmosphere by the process of transpiration.  Seemingly extravagant in their use of it, plants only recirculate a small amount of their transfer medium, water.  (This is a very simplified rendering of the actual processes that take place before our eyes and are not yet fully understood.)