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FATE AND EFFECTS OF PHOSPHORUS ADDITIONS IN SOILS UNDER N2-FIXING RED ALDER
Citation:
Compton, J E. AND D. W. Cole. FATE AND EFFECTS OF PHOSPHORUS ADDITIONS IN SOILS UNDER N2-FIXING RED ALDER. BIOGEOCHEMISTRY. Kluwer Academic Publishers, Hingham, MA, 53:225-247, (2001).
Description:
Soil phosphorus (P) dynamics are controlled by the interaction of geochemical, biochemical and biological processes, and changing species composition or management may alter the relative importance of these processes. We examined the role of these processes in two plantations of the N2 -fixing tree red alder (Alnus rubra) by76 comparing soil P fractions in control and P-fertilized soils (400 kg P ha-1). History of the plantations varied such that sites were previously occupied by alder or non-fixing Douglas-fir (Pseudotsuga menziesii). Without fertilization, the soil with a longer period of alder influence had more organic P (P ) and less sorbed inorganic P (Na OH-extractable Pi and HCP3-extractable Pi ). Fertilization increased total P, and 88% of the fertilizer was accounted for in the surface mineral soil. Sorbed P1 accounted for 55-60% of P retained in the soil, independent of site history. However fertilization increased CHCl3 -P and HCO3-P1 only in the soil with short-term alder influence. While P was 35-70% of soil P in unfertilized plots, added P was not converted into P . Site history or P addition did not influence phosphatase activity. Fertilization increased the decomposition of the organic horizon (p<0.06), suggesting that late-stage decomposition may be P-limited in these N-rich soils. On the time-scale of a few years, sorption and desorption of inorganic P appears to be the most important mechanism controlling the distribution of added P. Organic P accumulation is expected to occur over a longer time frame, linked to the production and turnover of organic matter.