Short- and long-term nutritional effects and retention of potassium derived from fertilizer in a sugar maple stand in southern Quebec

Abstract

The short-term (1–3 years) and long-term (23 years) effects of liming combined with potassium (K) fertilization on forest nutrition and K cycling were examined in a sugar maple (Acer saccharum Marsh.) stand in southern Quebec. Sugar maple leaves were sampled annually from 1988 (prefertilization year) to 1991 and in 2011–2012. Ten understory plant species, sugar maple sapwood, and soils were also sampled in 2012 and analyzed for K, calcium (Ca), magnesium (Mg), and rubidium (Rb). The recovery of fertilizer K was determined using the Rb/K reverse tracer method. Fertilization neither increased growth nor maintained higher sugar maple leaf K levels over the long term; however, leaf K to Ca and K to Mg ratios were still higher in fertilized plots than in control plots in 2012. The percentage of leaf K derived from fertilizer peaked 3 years after fertilization (36% ± 5%) and was down to 1989 levels by 2012 (15% ± 6%). Understory vegetation generally showed no differences in leaf K concentration between treatments, but percent K from fertilizers was greater than 25% in several species. There was no significant effect of fertilization on soil K, Ca, and Mg availability by 2012. Our results suggest that significant amounts of fertilizer K are still present on the site after 23 years but that base cation levels in leaves and upper soil horizons have returned to near prefertilization levels except for a slight enrichment in K. Although small, the effects of fertilization with liming on soil fertility and plant nutrient status in a maple stand can be long lasting.