Fall nitrogen application has long been promoted within the turfgrass industry to improve stand density. Researchers conducted a field study on four well-managed horse farm pastures in the Central Bluegrass region of Kentucky from September 2006 through March 2007 and repeated again during the same timeframe in 2007 and 2008. The objective of this study was to determine if fall nitrogen application improves forage stand density the following spring in horse pastures.
Nitrogen treatments included a series of fall nitrogen applications in late September and/or early November at rates of 30 or 60 pounds of nitrogen per acre. Two methods were used to objectively measure forage cover, which included fall and spring cover of desirable forage species: Kentucky bluegrass (
Poa pratensis), orchardgrass (
Dactylis glomerata), tall fescue (
Lolium arundinaceum), and white clover (
Trifolium repens). Weed species were measured, but not included in this analysis.
Both methods, visual percent cover and point-quadrat, were positively correlated. As a result, only visual percent cover data were used in the analysis due to ease of measurement and time efficiency.
Nitrogen treatments applied in fall 2006 showed a significant effect across all farms for March 2007. Fall split-application in September and November at 30 and 60 pounds of nitrogen per acre (each month) provided significantly more forage cover than a single application of 30 pounds of nitrogen per acre in September or November and the control. Single applications of 60 pounds of nitrogen per acre in September or November resulted in significantly more forage cover than the control. In treatments made the fall of 2007 and analyzed in the spring of 2008, there was no significant treatment effect.
In conclusion, these results suggest that forage stand density of cool season horse pastures in Kentucky can be improved with 30 pounds of nitrogen per acre applied in late September and again in November. Single nitrogen applications of 60 pounds of nitrogen per acre can provide similar benefits when applied in either late September or early November. Further research is necessary to validate these results within the region and in different growing seasons.
For further reading: Walker, K.S.; Bigelow, C.A.; Smith, D.R.; Van Scoyoc, G.E.; and Reicher, Z.J. 2007. Aboveground responses of cool-season lawn species to nitrogen rates and application timings. Crop Science 47: 1225-1236.
Collins, M. 1991. Nitrogen effects on yield and forage quality of perennial ryegrass and tall fescue.
Agronomy Journal 83:588-595.
Landschoot, P.J., and Waddington, D.V. 1987. Response of turfgrass to various nitrogen sources.
Soil Science Society of America Journal 51:225-230.
Ledeboeer, F.B., and Skogley, C.R. 1973. Effect of various nitrogen sources, timing and rates on quality and growth rate of cool-season turfgrasses.
Agronomy Journal 65:243-146.
Ray Smith, PhD, is an associate professor and forage extension specialist at the University of Kentucky. Other staff involved in the study were graduate student Laura Schwer, BS; faculty member Tom Keene, BS; former graduate students Jessie Morrison, MS, and Chengjun Huo, PhD; and staff members Joy Lourie, MS, Gene Olsen, MS, and Gabe Roberts.
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