Phosphorus Uptake in Young Pitch Pine (Pinus rigida Mill.)1
Phosphorus sorbed by young pitch pines was related to water-soluble P, P extracted by 0.002 n H2SO4, by HOAc-NaOAc or by NH4F-HCl in the rooting zones of these trees. Average annual P requirements were approximated by the three acid-extracting agents but water-soluble P in the root surface zone was considerably less than the annual uptake. Mean P concentration of the soil solution immediately adjacent to the root surface was estimated to be about 0.5 ppm. There appeared to be an interaction between P and Ca which resulted in reduced P uptake with increasing Ca concentration. Increased sorption of both P and Ca was associated with increased root surface. The results suggest that apatite or apatite-like compounds may have served as a source of P but attempts to verify presence of apatite in the soil were inconclusive.
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