Effect of Irrigation Interval on St. Augustinegrass Rooting1

Abstract

AbstractIrrigation is an integral part of a turfgrass management program. Turfgrass rooting characteristics within the soil profile determine how much soil moisture is available to support turfgrass growth. Determination of optimum irrigation intervals and the effects on turfgrass rooting will help provide better utilization of irrigation water resources. Rooting response to irrigation intervals was studied on ‘Floratam’ St. Augustinegrass [Stenotaphrum secundatum(Walt.) Kuntze] during the 1980 and 1981 growing seasons. Root mass and length on a dry‐weight basis were determined in 15‐cm profile increments to a depth of 75 cm from field plot samples at beginning and end of the study period. Treatments received the same irrigation volume but irrigation interval was every 2, 3, 4, or 6 days.Root mass and length density were unaffected by irrigation treatments during 1980. Total root mass density decreased 42% and root length density decreased 37% within the profile on a land‐area basis from beginning to end of the study period. Over 40% of the root mass occurred below 30 cm in the profile.Root mass density increased during 1981 from initial to final sampling for all profile depths except 60 to 75 cm but there was no treatment effect. In contrast to 1980, only 9% of the roots were distributed below 30 cm in the soil profile. Root length density increased for the 30‐ to 45‐cm and 45‐ to 60‐cm depths but was unchanged for the other depths. Total root mass density on a land‐area basis increased for all treatments but total root length density did not. This indicates that with the irrigation volume applied, St. Augustinegrass increased root size but not root length, regardless of irrigation interval. This would afford an advantage in survivability but not in drought avoidance.