Nitrogen is the mineral nutrient required in greatest amounts by tall fescue and the one least likely to be supplied by ambient conditions (see Chapter 6 and Chapter 7). Since established tall fescue turfs require more N than P and K, and more K than P, fertilizers with N/P2O5/K2O ratios of 5:1:2, 4:1:2, 4:1:3, and 3:1:2 are commonly recommended (URI Greenshare, 2000; Goatley et al., 2004; Relf, 1997; Street and White, 2000). Although the N requirement may vary among cultivars, tall fescue requires a medium level of N fertility when compared with other turfgrass species. Depending on intensity of culture, it requires from 2 to 5 g N/m2 (0.4 to 1 lb N/1,000 ft2) per growing month (Beard, 1973). In Mississippi, the application of 10 g N/m2 (2 lb N/1,000 ft.2) in March and September resulted in higher shoot density and chlorophyll content in a tall fescue turf maintained at a 6.4-cm (2.5-in) mowing height than the application of 5 g N/m2 (1 lb N/1,000 ft2) in March and September (Kranz and Philley, 1989). Changes in the rate of extension of tall fescue leaves can occur with very little, if any change in nonstructural carbohydrate concentrations within the leaf intercalary meristem. In Missouri, the application of 336 kg N/ha (300 lb N/acre) resulted in a 140% higher leaf elongation rate than in plants receiving 22 kg N/ha (19.5 lb N/acre) (Volenec and Nelson, 1984). Total nonstructural carbohydrates of leaf meristems averaged 44 and 39% of the dry weight for low-N and high-N plants, respectively. Concentrations of soluble proteins were lower in meristems of low-N plants than in those of high-N plants. The N requirement of tall fescue turfs can be met by granular or foliar applications of highly water-soluble or extended-release N sources (Table 26-2).


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Table 26-2. Common sources of N in turfgrass fertilizers.




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