TIFGREEN BERMUDAGRASS RESPONSE TO LATE-SEASON APPLICATION OF NITROGENAND POTASSIUM

Late-season application of N to bermudagrass (Cynodon dactylon x trans vaalensis Burtt-Davey) putting greens are often made in an attempt to extend turfgrass growth and color. Research was conducted to evaluate the physiological and morphological responses of bermudagrass to late- season application of N and K. Application of 0, 4.9 and 9.8 g N m-2 i n factorial combination with 0, 4.1, or 8.2 g K m-2 were made in Octob er of 1989, 1990, and 1991. Following fertilizer application, measurem ents of fall and spring turfgrass color, to nonstructural carbohvdrate (TNC) concentrations, and leaf tissue concentrations of N, P, and K w ere made. No changes in turfgrass color or TNC levels were observed fo r any level of K fertilization Application of 4.9 or 9.8 g N m-2, alon e or in combination with K improved fall turfgrass color through Octob er for each trial, and gave significantly higher spring turfgrass colo r ratings. Rhizome TNC levels declined linearly in December 1989 as N levels increased from 0 to 9.8 g m-2. There was a quadratic response i n TNC levels across N fertility levels in March 1990. No significant d ifferences in TNC levels were measured for any N level for 1990 and 19 91 in December or March, although N at 9.8 g m-2 tended to give lower rhizome TNC levels as compared with 0 or 4.9 g m-2 of N. Nitrogen appl ications provided a linear increase in N, P, and K concentrations in t he leaves. Late-season application of N improved fall and spring bermu dagrass color, and generally had little effect on rhizome TNC levels w hen measured in December or March.