NUTRIENT CYCLING IN A RED PINE PLANTATION 39 YEARS AFTER POTASSIUM FERTILIZATION

Red pine (Pinus resinosa Ait.) plantations planted in the late 1920s and early 1930s at the Pack Forest near Warrensburg, NY, showed severe nutrient deficiency symptoms after a few years. Numerous investigations revealed the soil to be extremely K deficient, due to a century of agricultural use. The present study was undertaken to describe long-term effects of K fertilization and to more completely characterize nutrient cycling in K-fertilized plantations and thus describe mechanisms responsible for the longevity of the K-fertilization response. In 1948, three 0.04-ha plots were established; two were fertilized with either 59 or 118 kg ha-1 K (designated LO and HI, respectively) and the third left untreated (CTL). Fertilization increased radial increment for Approximately 10 yr and resulted in increased basal area and tree height. In 1987 (39 yr after fertilization), soil exchangeable K in the upper 15 cm of the mineral soil remained greater in fertilized plots. Aboveground biomass in 1987 was 129, 164, and 190 Mg ha-1, respectively in CTL, LO, and HI. In LO and HI, the N, P, Ca, Mg, and Na contents were 20 to 50% greater than in CTL. There was twice as much K in the aboveground vegetation of LO and HI than CTL, due primarily to increased foliar biomass. This was reflected in the greater litterfall as well as throughfall and stemflow fluxes of K in LO and HI relative to CTL. Fertility of the plots was maintained by the efficient cycling of nutrients, especially K, in the ecosystem.