Distribution and cycling of macronutrients in a Pinusresinosa plantation fertilized with nitrogen and potassium

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Abstract
Fertilization with 100 kg K ha-1 as KCl and 100 kg N ha-1 as NH4NO3 resulted in an 11% increase in aboveground biomass and a 32% increase in aboveground production 4 years following fertilization of a 33-year-old red pine (Pinus resinosa Ait.) plantation in central Wisconsin [USA]. The greatest absolute increase in dry matter occurred in the foliage, followed by the sapwood and the live branches. Fertilization increased all macronutrients (N, P, K, Ca, Mg) in the aboveground tissues. The increase was greatest for N, followed by Ca, K, Mg, and P. The net gains in macronutrients in the live branches and the sapwood were due not only to increases in dry matter production but also to increases in nutrient concentrations. However, the increases in macronutrients in the foliage were related to an increase in foliage mass rather than to changes in foliar concentrations. Whereas 26 kg K ha-1 (26% of applied K) was recovered in the biomass and forest floor 4 years after fertilization, 107 kg N ha-1 (107% of applied N) was recovered in these pools. The greater recovery of N than the amount applied was attributed to additive errors associated with preparation of nutrient budgets. Fertilization increased leaching losses of all macronutrients especially .**GRAPHIC**. and Ca2+, at the bottom of the rooting zone. However, leaching losses returned to levels measured in the control stand within 5 (K+, .**GRAPHIC**. to 14 months .**GRAPHIC**. Ca2+) following fertilization.