Fertilizer Effects on Annual Grass in Wet Sedge-Grass Vegetation Site, Susitna Basin, Alaska, U.S.A.

Abstract

Fertilizer trials on a disturbed, wet sedge-grass vegetation site in south-central Alaska indicated that N, P, and K were all deficient. Fertilizer and seed (common annual ryegrass, Lolium temulentum) were broadcast in l-m²-square plots in a randomized complete block design with three replicates. Treatment levels were equivalent to 0, 100, and 200 kg N ha^–1; 0, 75, and 150 kg P ha^–1; and 0, 60, 120 kg K ha^–1. Greatest responses for aboveground biomass and height occurred when all three nutrients were applied. Greatest cover occurred when both N and P were applied with or without K amendments. Positive responses for biomass and height required both N and P while cover responses required only N, P, or low K. Potassium application without N tended to suppress plant responses although these results were not statistically significant. Interactions among nutrients were significant in many cases. Nonsignificant responses occurred when only a single nutrient was applied. This indicates that N, P, and K were all deficient on this site. Disparate responses of the measured parameters indicate that different measures of plant growth may be more sensitive to some nutrient deficiencies than to others.