Yield of Kentucky Bluegrass (Poa pratensis) as a Function of Its Percentage of Nitrogen, Phosphorus, and Potassium¹

Abstract

Kentucky bluegrass clippings were obtained from experimental plots containing a control plus treatments conforming to a 5 × 5 × 5 central composite design with N, P, and K fertilizer variables over a period of 2 years. A sample of each clipping from each plot each year was saved for chemical analysis. The samples were then ground, mixed, subsampled, and analyzed for their percentage of N, P, and K. A regression analysis was computed, and a prediction equation with bluegrass yield as a quadratic function of its average percent N, percent P, and percent K was determined. The resulting prediction equation had an R2 of 0.7419 and was used to estimate “critical percentages” for N, P, and K in Kentucky bluegrass. The technique developed would be expected to be applicable to other crop and soil conditions.

GROWTH OF ANDROPOGON SCOPARIUS (LITTLE BLUESTEM)IN PHOSPHORUS DEFICIENT SOILS

“…The critical P concentration of o. 14% for Andropogon is considerably below the critical concentration of 0.25 % P iorPoapratensis determined by Walker and Pesek (1967). It is also below critical P concentrations for several other crop species which range from 0.25% for corn to 0.35% for soybeans and alfalfa (Melsted, Motto and Peck, 1969).…”

Parameters of nitrogen use efficiency of Kentucky bluegrass cultivars at different N levels under deficit irrigation

“…Following this traditional definition, NUE in turfgrass is essentially the inverse of nitrogen concentration in the clippings. One of the limitations in using this definition is the failure to recognize NUE changes over time as a perennial because most research measured nitrogen concentration only once over the period of investigation (Bertauski et al, 1997; Bushoven & Hull, 2001; Jiang & Hull, 1998; Walker & Pesek, 1967; Zemenchik & Albrecht, 2002). Vitousek (1982) pointed out the differences between annuals and perennials on N use by plants and defined the NUE for perennials as the amounts of organic matter lost from plants or permanently stored within plants per unit of nitrogen lost or permanently stored.…”