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This article in SSSAJ

  1. Vol. 44 No. 6, p. 1200-1204
    Received: Apr 14, 1980
    Accepted: June 30, 1980

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Measurement of Fertilizer Phosphorus Residues and Its Utilization1

  1. E. D. Spratt2,
  2. F. G. Warder3,
  3. L. D. Bailey2 and
  4. D. W. L. Read3



A values and sodium bicarbonate (NaHCO3) extraction soil tests were used to determine phosphorus (P) levels over 8 years on four soils which had been treated with 0, 100, 200, and 400 kg P/ha. The tests correlated highly with each other and indicated the decline of residual fertilizer-P over years as the soils were cropped. Reliable predictions for the duration of the beneficial effects of large amounts of fertilizer-P could be made for the two Manitoba soils where cropping was continuous (wheat-flax) but not for the Saskatchewan soils where fallow was included (wheat-fallow). By using the linear equation of NaHCO3 soil tests vs. time (years), it was predicted that 100, 200, and 400 kg P/ha would last about 6, 9, and 13 years, respectively, before further fertilizer-P inputs were needed to maintain wheat production. Longer durations were predicted for 200 and 400 kg P/ha when curvilinear relationships were used, averaging 11 and 22 years, respectively, giving better economic feasibility. These soil testing techniques may be used on calcareous soils to minimize current fertilizer-P inputs for wheat where residual fertilizer-P has accumulated.

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