Phosphate Fractions in Calcareous Soils as Altered by Time and Amounts of Added Phosphate1
- M. L. Hooker,
- G. A. Peterson,
- D. H. Sander and
- L. A. Daigger2
Tie-up of water-soluble P is very rapid in calcareous soils. To determine the residual effect of high rates of applied P several experiments were established on soils ranging from 0.1 to 16.5% calcium carbonate equivalents (CCE). At each location an experiment was established with four rates of P (25, 50, 100, and 500 kg/ha). The soils were sampled annually for periods of up to 5 years. These soil samples were fractionated to determine the concentration of P in the various inorganic P fractions, using the techniques of Syers et al. (1972), as affected by rate of P application and time after application.
Over time there was a decrease in the more soluble, plant-available fractions indicating a shift of P from extractable to nonextractable forms. Also the various P fractions were correlated with two of the more commonly used soil methods, Bray and Kurtz no. 1 and the Olsen NaHCO3. As the CCE of the soils increased the correlation of the Bray and Kurtz no. 1 method with the fractions considered most available to plants decreased while the correlation of the Olsen method remained high.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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