Mwakisimba, John2025-09-242025-09-241999https://www.suaire.sua.ac.tz/handle/123456789/7028DissertationPhosphorus is mostly supplied in the form of water soluble fertilisers which are very expensive. Thus resource poor farmers can not afford it. The price of Minjingu phosphate rock (MPR) is relatively lower and may substitute water soluble P fertilisers if found to be agronomically comparable to the traditional P sources. A study was conducted to investigate the extent of M'PR dissolution and extractability of P after dissolution of MPR and to determine soil factors controlling the dissolution of MPR and subsequent levels of extractable P in eleven Tanzanian soils. Also the adsorption characteristics of the experimental soils were determined. P adsorption maxima of the experimental soils ranged from 375.4 to 4110.2 mg P/kg and were directly influenced by A12O3. The amounts of P adsorbed at 0.2 pg P/ml ranged from 22 to 710 pg P/g. The soil with the highest P adsorption maximum had the highest P adsorbed at 0.2 pg P/ml. On the other hand, soils with substantial amount of P in equilibrium solution at zero added P had low P requirement. Some of the soils with high P adsorption maxima had low P requirement. The extent of MPR dissolution in the eleven soils tested ranged from 34 - 97 % of the applied P after 70 day (d) of incubation. High percentage (83%) of the variation in MPR dissolution was accounted for by three soil properties namely percent Ca saturation, OC and P retention capacity. Bray 1 P in the experimental soils ranged from 7.3 to 71.0 % of the dissolved P after 56 days of incubation, with an average of 29.6 % suggesting a high degree of fixation. Bray 1 P was also significantly related to exchangeable Al, Al saturation, soil pH, soil pH buffering capacity and OC. However none of these soil properties accounted for > 50 % of the variation in Bray 1 P. This implies that none of the independent variables tested adequately predicted the dependent variable. Results from this study indicate that MPR has high solubility in acid soils of pH < 5.8 and should thus be evaluated for direct application under field conditions.enPhosphorusSoilsSoil propertiesThesis