Summertime thirst includes your lawn (05-29-2006)

We know it is important for us to drink plenty of fluids particularly during the heat of summer activities to prevent dehydration. Our lawns are no exception, and as the days become warmer our lawn’s demand for water will be even more critical. As long as adequate water is available to our warm season lawns they are happy with 90-degree temperature days.

Understanding the functions of water to a lawn will help determine when your lawn needs water. A healthy lawn is a tremendous air conditioning system as it transpires water to moderate temperature changes of plant cell protoplasm, maintain cell turgidity and opening of stomata. Water is essential for the uptake and serves as the transport medium for nutrients into the plant. Water serves as the solvent or catalyst for metabolic processes and is required for photosynthesis. Water is also necessary for seed germination and the survival of beneficial bacteria and fungi that help decompose mowed leaf clippings. Therefore, when all of these functions are going on at the same time the lawn will demand and require the highest level of water.

It is often asked, how much water does a lawn need each day or week? As a general rule the answer is somewhere between one to three tenths of an inch per day, or one to one and a half inches per week when the turf is actively growing. Of course, these amounts vary depending on a host of environmental and physical conditions such as temperature, wind, clouds, traffic, soil type, turf species, etc.

How and when we water is also important to its utilization and the health of the turf. When supplemental irrigation water is needed it should be applied in thorough less frequent applications to deeply moisten the soil to a depth of three to four inches to encourage a stronger deep-rooted turf. A light sprinkle each day only encourages shallow rooting and greater evaporation loss. Watering should be done early enough in the day to allow the turf leaves to dry before nightfall to reduce fungal disease proliferation.

Excess water can often be as detrimental as too little water. Compacted soils with poor internal soil drainage will reduce soil oxygen resulting in lower root mass and depth. With a much smaller, stressed root system the turf plant can’t take in the water and nutrients needed for optimum growth and appearance.

Published May 29, 2006

Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. wwells@ext.msstate.edu