Kosia, Efraim Nyalinga Michael2025-12-042025-12-042003https://www.suaire.sua.ac.tz/handle/20.500.14820/7157Masters' ThesesA study was conducted in the laboratory to assess changes in soil phosphorus fractions in relation to phosphorus sources and to evaluate the influence of those fractions on residual phosphorus availability and uptake of selected nutrients. Residual P was compared to fresh P application at rates of 60 mg P kg'1 and 180 mg P kg'1 to determine their influence on dry matter yield (DMY) and the uptake of P, Ca, K, and Mg. Three soils with high P fixing capacity, Sasanda (Umbric Andosol), moderate fixing capacity, Suluti (Rhombic Acrisol) and low fixing capacity, Nkundi (chromic Acrisol) from the Southern highlands of Tanzania were used. A portion of soil (1.0 g) was sequentially extracted with deionized water, 0.5 M sodium bicarbonate (NaHCOj), 0.1 M sodium hydroxide (NaOH), 1.0 M hydrochloric acid and a combination of concentrated sulphuric acid and hydrogen peroxide (H2SO4 + H2O2). Both organic and inorganic P were determined in NaHCCh and NaOH extracts. The results indicated that, the release and distribution of various P fractions were dependent on the P source and soil characteristics. In Sasanda and Suluti soils, TSP gave significantly higher effects than MPR on H2O-P, 0.5 M NaHCOj-P and 0.1 M NaOH-P but opposite results were obtained for HC1-P and H2SO4 + H2O2-P fractions. The trends of most P fractions in Nkundi soil were opposite of those in Sasanda and Suluti soils except for NaOH-Po and H2SO4 + H2O2-P which were similar. The FeO-Pi was highest in Nkundi and lowest in Sasanda. The results also showed that high rates of fresh applications of TSP significantly increased DMY while low rates led to only slight increases in DMY over their respective residual sources. Dry matter yield increased significantly (< 0.05) at high application rates in Sasanda, while there was only slight increase over low residual application rates of MPR. MPR caused slight increases in DMY and Ca uptake over TSP, and Ca uptake increased with P application rates. Calcium concentration in the plant was at sufficiency level. Potassium concentration in plant was at deficiency level in all soils, and its uptake decreased with an increase in Ca concentration in plants. Phosphorus caused a slight increase in Mg concentration in plants probably due to depressed K uptake. From this study it was concluded that P fractions were influenced by both P sources and soil properties. Minjingu PR had higher residual effect on DMY and uptake of P and Ca than TSP. Phosphorus influenced Ca and Mg nutrition while K decreased with an increased Ca uptake from the soils. The data suggest that maintenance application of P is required in the soils that had residual P. In addition. other nutrients should be calibrated along with P sources to avoid inbalance ol nutrients. Further research is required to assess the relationship between P fractions and soluble P forms.enSoil phosphorus fractionsPhosphorus sourcesResidual phosphorus availabilityThesis