Evaluation of the Parameters of Soil Phosphorus Availability Factors in Predicting Yield Response and Phosphorus Uptake1
- R. C. Dalal and
- E. G. Hallsworth2
The importance of quantity, intensity, capacity, and rate factors of soil P availability to account quantitatively for the variation in P uptake and wheat grain yield in pot and field experiments was studied. Among the parameters of the quanitity factor (L, E, Ec, E1.0, Q0 value, NH4F-P, NaOH-P, H2SO4-P, organic P, Olsen P, Colwell P, carbonate P, and anion-exchange resin, AER-P), L value was found to be highly correlated with P uptake at 35 and 150 days after planting (maturity) when all the soils were considered. However, the carbonate P (soil P extracted for 16 hours with 0.25M NaOH-0.1M Na2CO3 at a soil/solution ratio of 1:100) was found to be the best parameter of the quantity factor when the soils containing high amounts of hematite/goethite (> 20%) were excluded. The parameters of the intensity factor (0.01M CaCl2 soluble P, aH2PO4i and phosphate potential) were significantly correlated with P uptake at early growth (35 days) whereas the parameter of the capacity factor (maximum buffering capacity, Mb) was bezter correlated with P uptake at the later stage (150 days). The rate factor, as measured by AER was better correlated with P uptake at 35 days than with P uptake at 150 days after planting. The quantity factor as measured by the carbonate P accounted for 75 and 93% of the variation in P uptake and grain yield, respectively. The capacity factor, Mb when combined with the quantity factor accounted for more of the variation in P uptake (150 days) from 75 to 86%. The intensity and the rate factors had a smaller effect.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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