Lawn Water Use
Water is an essential ingredient of all living cells and when combined with CO2 in the presence of sunlight and chlorophyll results in photosynthesis – the food making process of all living, green plants. Figure 9.1 illustrates the photosynthetic process.
Figure 9.1. Photosynthetic process.
Turfgrasses are about 90 percent water by weight. All nutrients taken into lawn grass roots from the soil are in solution (i.e., dissolved in water). Once roots have absorbed nutrients into the plant, they are moved (translocated) to the individual cells of stems, leaves and other grass plant parts where they are involved in numerous plant growth processes. Water vapor eventually diffuses out of the leaf through small pores called stomata. These small pores are spaced close together on upper and lower leaf surfaces. This water-loss through the plant, known as transpiration, helps cool the turfgrass plant and its surrounding microenvironment.
Lawn grasses differ in both physical properties that influence water needs and biochemical processes that determine water use. Thus, lawn grasses have a combination of structural and chemical characteristics that make them more or less efficient users of water, as well as more or less drought tolerant.
Among our commonly used lawn grasses, the fine-leaved fescues and older, common types of Kentucky bluegrass are more tolerant of dry conditions than either perennial ryegrass or most of the newer, improved types of Kentucky bluegrass. However, recent turfgrass breeding efforts have improved tolerance to drought stress in some of the newer varieties of Kentucky bluegrass. For more information on choosing turfgrass varieties see Chapter 4 Turfgrass Selection for a Sustainable Lawn.
The depth and extent of root development influences drought tolerance. A grass plant with a larger, more extensive and deeper root system has an increased volume of soil from which to obtain needed water. This would permit the grass to survive longer under drought conditions. Root development of our common, cool season lawn grasses is generally confined to the top foot of soil.
For more information on turfgrass biology see Chapter 3 Grass Plant Growth and its Relationship to a Sustainable Lawn.
Proceed to Determining Amount of Water to Apply