Effects of Nitrogen‐Potassium Levels on the Growth and Chemical Composition of Kentucky Bluegrass1

Abstract

AbstractThe performance of an apomictic strain of Kentucky bluegrass under eight fertility levels was studied during 1966 and 1967 under greenhouse conditions. Fertilizers were applied as nutrient solutions. Treatments included two nitrogen (65 and 130 ppm) and four potassium (0, 100, 200, and 400 ppm) levels in all factorial combinations. Clipping weights, weights of underground plant parts (roots and rhizomes) and tops, vigor scores, tiller counts, blade widths, and rhizome lengths were taken as measures of growth. Amounts of N, P, K, and C in leaf tissue were determined by chemical analysis.All growth measurements, except rhizome lengths under 130 ppm N, were increased by potassium when compared to the 0‐ppm K level. However, levels of K above 100 ppm were often detrimental under 65 ppm N and sometimes had little effect with 130 ppm N.N content of leaf tissue was increased by 130 ppm N while levels of K exceeding 100 ppm appeared to cause a slight, although significant decrease under both N rates. N and K had no significant effect on P content of leaf tissue. Added K increased the amount of K in leaf tissue up to the 200 ppm level. High nitrogen increased the K content significantly, but the increase was less than 0.2%.The balance between N and K appeared to effect growth responses. With 65 ppm N, 100 ppm K had the greatest effect on increasing growth measurements. With 130 ppm N, the balance requirement was less critical but the 200 ppm level gave the greatest growth measurement increases. The 400 ppm K level generally resulted in reduced growth regardless of N levels.