Abstract:
An incubation pot experiment was conducted at the Sokoine University of Agriculture, Morogoro,
Tanzania to study the effects of times of contact and rates of Minjingu phosphate rock (MPR) applied to a
Kanhaplic Haplustult on the release of P from the MPR. The soil was mixed with MPR at rat'es
equivalent to 0.0, 25.0, 37.5, 50.0 and 75.0 mg PI kg soil. The incubation periods were 30, 60, 90, and
120 days. The moisture content of the soil in the pots was maintained at about field capacity during the
incubation periods using distilled water. Release of P from the MPR increased with increase in MPR
rates and incubation periods. The interaction between incubation periods and MPR rates explained
about 86.8% of the variation in P release from the MPR. MPR rates accountedfor 76.6% of the release
of P, while incubation periods accounted for 10.3% of the dissolution. The soil pH and extractable Ca
were found to increase slightly with increase in MPR rates but decreased with increase in incubation
periods. The exchangeable acidity and exchangeable Al decreased with increase in MPR rates, and
slightly increased with incubation periods.
