Soil Science Collection

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Browsing Soil Science Collection by Author "Budotela, George Masanja Raphael"

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    Evaluation of minjingu phosphate rock as a source of phosphorus for grapevine production in Dodoma district Tanzania
    (Sokoine University of Agriculture, 1995) Budotela, George Masanja Raphael
    Experiments were conducted to assess the P status of selected soils of Dodoma district, Tanzania and the response of grapevine to P application. The experimental sites were Msalato A, Msalato-Manispaa and Veyula Makutupora. The studies included (i) the initial fertility characterization of the incubation study and (iii) experimental soils (ii) an a field trial which compared MPR and TSP as sources of P. Results from the characterization study showed that fertility status decreased with increasing distance from the tree trunk congruent to the location of the fertilizer band. In the incubation experiment, solubility of MPR was found to increase steadily with time until equilibrium was reached at about 45 days. At this time 52% of the applied MPR, equivalent to 260 mg P/kg had dissolved. Soil samples incubated with TSP at this time released 64% of soluble P. Calcium and Phosphorus sinks were demonstrated as important parameters which influenced P dissolution in the test soils. In the field trial, both TSP and MPR application increased grape yield significantly over the control with TSP giving higher yield than MPR. The relative agronomic effectiveness (RAE) value for MPR averaged 67%, suggesting that TSP had a higher fertilizer value. The study further demonstrated that P rates above 168 kg P/ha decreased grape yields at Veyula-Makutupora site while at Msalato A and Msalato-Manispaa sites yields continued to increase. From these findings, it was concluded that: in addition to N, P application was needed in order to optimize grape yield in Dodoma district and a tentative rate of 168 kg P/ha is recommended. Minjingu PR was found to be a promising substitute for TSP but assessment of residual effects should be made before a definite recommendation can be made. Further research should be conducted to increase P use efficiency.