EFFECTS OF IRRIGATION FREQUENCY, SALINITY OF IRRIGATION WATER, AND SOIL TYPE ON GROWTH AND RESPONSE OF BERMUDAGRASS

An important irrigation management decision when using saline wastewaters is the proper selection of the irrigation frequency. The objective of this research was to determine the impact irrigation frequency had on the growth of common bermudagrass (Cynodon dactylon (L.) Pers.) when irrigating with saline waters of three different concentrations on three different soil types. Bermudagrass was grown for an 18-month period as an extension to a previous 2-year salinity study. Bermudagrass was grown in large columns packed with three different soil types (sandy loam, silt loam, and clay). Saline water was synthesized and applied at three different salinity levels (electrical conductivities of 1.5, 3.0, and 6.0 dS m-1). Irrigations were applied at a rate beyond measured evapotranspiration to establish a leaching fraction of 0.15 on all columns. Irrigations were applied at either one, two, or four times per week. Soil salinity was measured in soil cores taken before and after the experiment. Dry matter of weekly grass clippings was measured and recorded throughout the 18-month period. Also measured throughout the experiment were leaf xylem water potentials, soil matric potentials, diffusive resistance, and soil oxygen diffusion rates. Results indicated that irrigation frequency had a significant impact on the growth response of bermudagrass. In both the sandy loam and silt loam soils, dry matter yield increased as the irrigation frequency increased at all irrigation salinity levels. In the sandy loam soil EC(i) and irrigation frequency accounted for 88% of the variability in yield (p = .01). However, in the clay soil, yield decreased as the irrigation frequency increased at all irrigation salinity levels, with EC(i) and irrigation frequency accounting for 83% of the variability (p = .01). It was suggested that the negative response to increased irrigation frequencies on the clay soil was related to poor soil aeration, since a significant multiple correlation existed between EC(i) and oxygen diffusion rate on dry matter yields (p = .001).