No data exist on lime and trace element requirements for tall fescue seed production. Generally nutrients are most available at pHs of 5.8 to 7.0. Agricultural limestone should be applied and mixed in the top 15 cm of soil if the pH falls below 5.6. Over-liming can lead to deficiencies in trace elements such as Mn and Zn. At four sites with soil B of 0.2 to 0.3 mg/g and with flag leaf B concentrations of 9 to 14 mg/g, seed yield showed no response to a B fertilizer containing 1.4 kg B/ha (Mellbye and Gingrich, 2000; Mellbye et al., 2001).
There is little published information on levels of P, K, and S required for seed production. A soil available P of at least 15 mg/g (Olsen P extraction) is generally thought to be adequate, but this needs to be validated.
Nitrogen is the most important nutrient for tall fescue seed crops. First-year seed crops require a total of 180 to 200 kg N/ha, while second-year and multi-year crops need 230 to 250 kg N/ha. Because autumn and early winter tiller development and survival are important in tall fescue, higher amounts of autumn N are required than for perennial ryegrass (Lolium perenne L.). In Oregon turf tall fescue, no yield advantage was observed from using more than 150 kg N/ha in the spring in three trials (Fig. 23-2), each with a different cultivar (Young et al., 2000, 2001).
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Fig. 23-2. Spring N response in Oregon. Mean of five sites with three different turf tall fescue cultivars, when 30 kg N/ha had been applied in autumn (derived from Young et al., 2000, 2001).
Nitrogen recommendations for Oregon take into account N supplied from soil, typically 55 to 110 kg N/ha annually, depending on soil type and stand age (Hart et al., 2005). Soil N supply usually is highest after tillage, about 110 kg N/ha for the first 2 yr of a stand, decreasing to about 55 kg N/ha in subsequent years. Poorly drained soils with more than 5% organic matter supply more N than well-drained soils with lower organic matter content.
Twenty-five to 45 kg N/ha usually are applied at seeding in either spring- or fall-sown crops. In Oregon on-farm trials, fall N increased seed yield by an average of 190 kg/ha when compared with no fall N application. Fall N applied at rates greater than 45 kg/ha did not increase seed yield in field tests as long as adequate N had been applied in the spring. In Oregon, optimum tall fescue seed yields can be produced with spring applications of 100 to 155 kg N/ha. Although not essential for optimum seed yield, a split N application is recommended for uniformity, ease of management, and to accommodate crop uptake. Applications begin in late winter, as soils dry to field capacity and growth begins, and are completed by early spring.
No studies appear to have compared the N requirements of turfgrass with those of forage tall fescue for seed production. General N recommendations for forage tall fescue in New Zealand have been based on 200 to 230 kg N/ha for seed crops that are grazed in fall and winter:
Autumn: 100 kg N/ha split into two applications
Late Winter: 30 kg N/ha applied when soil temperatures reach 5°C
Spring: 70 to 120 kg N/ha in two or three applications
This approach is based on the expectation that high autumn N will encourage autumn and early winter tillering. Excessive spring N applications will result in new tillers that will be vegetative, owing to a lack of the cold induction which is needed for the initiation of reproductive tillers.
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