Nutrient Cycling in a Red Pine Plantation Thirty-Nine Years after Potassium Fertilization
- James P. Shepard and
- Myron J. Mitchell
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 ∼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.
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