| Summary: | 博士 === 國立臺灣大學 === 農業化學系 === 84 === This research aims at understanding kinetic changes of soil
available phosphorus after fertilization and to establish
kinetic model for fertilizer P availability index (Fl). Effects
of temperature, moisture, types of fertilizer and environment
on fertilizer P availability index were also evaluated. An
improved corrective fertilizer recommendations based on kinetic
model is proposed. Fifty soils from major cultivated areas
throughout Taiwan were treated with five rates of P and
incubated for 0 to 180 days and tested for Bray1 P or Olsen-P.
At all incubation intervals, for all soils, the extractable P
was linearly correlated with applied P. All correlation
coefficients were greater than 0.98. The slope of these linear
regressions is defined as Fertilizer P Availability Index.
Changes of Fertilizer P Availability Index with time were best
fitted to Elovich kinetic model as: Fertilizer P Availability
Index (Fl) = a + b * ln ( t ), where t is incubation time (day)
and a, b are model parameters. To improve the accuracy of
estimation P requirements, the kinetic model of P availability
index was tested. Ten soils were first treated with five rates
of P fertilizer, at 90 days after incubation, each soil
received same amount of P (90μg P/g soil) and Bray1 P or Olsen-
P were measured at 180 days after incubation. Predicted
available P values from the kinetic model were highly
correlated with actual amounts measured (r= 0.98). These
results indicate that the proposed kinetic model combined with
the linear relation between applied P and extractable P makes
possible a greatly improved recommendation for fertilizer
phosphorus.
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