Impaired water quality in the Chesapeake Bay and other surface waters due to excess phosphorus (P) is receiving scrutiny from state and federal environmental regulatory agencies. Although agricultural operations are considered the largest single source of P loading of the Chesapeake Bay (USEPA, 2010), fertilizer practices in urban and suburban areas are receiving more attention as a source of P contamination (Milesi et al., 2005; Schueler, 2010; Soldat and Petrovic, 2008). In response to environmental concerns and P restrictions, many fertilizer companies have reduced or eliminated P in synthetic turfgrass maintenance fertilizers; however, P is still present in organic and starter fertilizers.
Starter fertilizers typically contain higher amounts of P than maintenance fertilizers, and they are applied to the soil surface at the time of seeding to hasten the establishment of turfgrasses and improve root development. The use of starter fertilizers containing P is frequently recommended for turfgrass establishment by university extension publications and by public and private soil test laboratories and consulting agencies. Often, recommendations for applying P-containing starter fertilizers at the time of establishment are made regardless of the nutrient status of soil (Hardebeck et al., 2005). However, data from cropping systems and turfgrass research suggest that, at certain sites with high P according to soil test results, high-P starter fertilizers may not provide significant improvements in the crop yield or rate of turf establishment compared with N fertilizer with low amounts of P, fertilizer with no P, and, occasionally, fertilizer with no N and no P (Reicher et al., 2000; Roth et al., 2006; Vetsch and Randall, 2000).
Improved establishment of cool-season turfgrasses following incorporation of high rates of P fertilizer into soils containing low amounts of P has been well-documented. Christians et al. (1981) reported an increase in groundcover of kentucky bluegrass (Poa pratensis L.) resulting from 540 kg·ha−1 P applied to soil containing low P. Turner and Waddington (1983) found that the application of P in the range of 160 to 400 kg·ha−1 is beneficial for promoting rapid turfgrass establishment (groundcover, yield, and quality) in silt loam soil with low P.
Although the aforementioned studies showed improved establishment of cool-season grasses following P applications in soils containing low P levels, responses to P fertilizer in intermediate-P and high-P soils (>50 mg·kg−1 Mehlich-3 P) are not as clear. Carroll et al. (2005) conducted greenhouse studies to determine the growth response of tall fescue seedlings to the addition of P in eight soils with high P according to soil test results (52 to 277 mg·kg−1 Mehlich-3 P) under different temperatures. Under warm temperatures, the growth of tall fescue increased linearly with increasing P rates, but no response to P additions occurred in soils with ≥163 mg·kg−1 Mehlich-3 P. The response of tall fescue to P additions under cool temperatures showed increased seedling growth after P fertilizer applications to soils with ≥163 mg·kg−1 Mehlich-3 P.
In a separate greenhouse study, Carroll et al. (2005) examined growth responses to P additions in soils ranging from 52 to 97 mg·kg−1 Mehlich-3 P under warm temperatures and found positive responses in all soils except for one with 97 mg·kg−1. The authors concluded that under warm temperatures and adequate moisture, the addition of P at seeding will have little impact on tall fescue seedling growth in soils with >97 mg·kg−1 Mehlich-3 P, but that seedling growth may increase with P additions in soils with >97 mg·kg−1 Mehlich-3 P under adverse growing conditions.
Hamel and Heckman (2006) conducted extensive greenhouse studies and two field experiments using soils from New Jersey to determine critical levels of P according to soil test results for the rapid establishment of kentucky bluegrass, perennial ryegrass (Lolium perenne L.), and tall fescue. The authors reported that critical P levels vary among species, with kentucky bluegrass having higher P requirements than tall fescue and perennial ryegrass. Critical soil test P values estimated from tall fescue and perennial ryegrass based on relative clipping yields were 170 mg·kg−1 for Mehlich-1, 233 mg·kg−1 for Bray-1, and 280 mg·kg−1 for Mehlich-3.
Two field seedling establishment experiments were conducted by Hamel and Heckman (2006) using the same soils as those in one of their greenhouse experiments. Findings from one experiment site showed a positive linear turf density response to the P rate for kentucky bluegrass, but not for perennial ryegrass. A significant treatment response and linear response for tall fescue density were found for only one of five rating dates. Results from the other site showed that kentucky bluegrass and perennial ryegrass were not responsive to P additions, but that tall fescue responded to increased P rates with increased turf density on two of six rating dates. The authors stated that these results represent an example of how the use of critical levels identified in greenhouse studies may have incorrectly predicted the need for P fertilization in the field.
A field study conducted by Reicher et al. (2000) investigated the influence of surface applications of N and P at typical starter fertilizer rates on kentucky bluegrass established on different seeding dates during late summer/fall and late winter/spring. The authors reported significant effects of the seeding date on establishment, but no effects were caused by the fertilizer treatments. Reicher et al. (2000) attributed the lack of response to fertilizer treatments to high fertility levels of the silt loam soil.
Hardebeck et al. (2005) conducted a 2-year field study to determine the effects of varying P and potassium (K) rates on the establishment of tall fescue. Tall fescue was seeded on three dates at two locations with different soil P and K levels. At the low P and K fertility location, the application of 98 kg·ha−1 P increased spring turf cover by 21% at plots that received no P during the September seeding date treatment. However, no yield or groundcover differences due to P were observed at the high-P site. The authors concluded that incorporating P at seeding should continue to be a recommended practice because it improves establishment in soils with medium to low P levels.
Previously cited reports demonstrated variability in the responses of cool-season grasses to P additions when established in soils with medium to high P levels according to a soil test. Some of the differences among studies may be due to grass species and cultivar, soil type, how the study was conducted (greenhouse vs. field), soil temperatures, and possibly other factors. Because public concern regarding P losses and water contamination has called into question standard fertilizer practices, including routine application of P in starter fertilizers, additional research is warranted to determine the influence of P on the establishment of cool-season turfgrasses.
The primary objectives of this study were to determine if P in starter fertilizer applied at the time of establishment influences groundcover and foliar growth of newly established tall fescue in silt loam soil with a range of P during late summer and fall and to determine changes in foliar tissue N and P and the P results of a soil test in response to P fertilizer applied at rates typical of starter fertilizer applications to turf. Tall fescue was of particular interest in this study because of its increasing popularity as turfgrass, and because its nutritional requirements have not been extensively studied in the northern area of the Chesapeake Bay watershed.
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