Spring Dead Spot and Burmudagrass Quality As Influenced by Nitrogen Source and Potassium
- P. H. Dernoeden ,
- J. N. Crahay and
- D. B. Davis
Little is known about the influence of cultural practices on spring dead spot, SDS, (Leptosphaeria korrae J.C. Walker & A.M. Smith) of ‘Tufcote’ and other bermudagrass [Cynodon dactylon (L.) Pers.) cultivars. The primary objective of this study was to assess NaNO3, (NH4)2SO4, NH4C1, CO(NH2)2, KCI, and the N sources plus KC1 in growth-chamber and field studies for their influence on SDS. In the growth chamber, Tufcote inoculated with L. korrae and fertilized with (NH4)2SO4 or KC1 exhibited a 24% increase in survivability when compared with unfertilized, inoculated plants. Field studies were initiated at Denton and Silver Spring, MD, in 1986. At Denton, improved SDS recovery was observed mid-June 1987, and enhanced spring green-up occurred in May 1988 where (NH4)2SO4, (NH4)2SO4 + KC1, and NH4Cl + KC1 were applied. Tufcote was established in 1986 at Silver Spring, but significant levels of SDS did not appear until 1988. In 1988, none of the treatments improved spring green-up, but all N treatments helped to speed turf recovery from SDS. NH4Cl + KCl enhanced spring green-up by >75% at Silver Spring in 1989 and 1990, and reduced SDS by >41% from late May to late June 1989 when compared with CO(NH2)2-treated or unfertilized plots. Other NH4-N treatments were equivalent to NH4C1 + KCI in improving spring green-up and reducing SDS in 1989 and 1990. A negative correlation between soil pH and spring green-up occurred at Denton (1988) and Silver Spring (1990), whereas percent of plot area injured by SDS was positively correlated with soil pH at Silver Spring in 1989. Data indicate that acidification of soil by NH4-N reduced the severity of SDS over time.
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