Department of Soil and Geological Sciences

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Browsing Department of Soil and Geological Sciences by Author "Amuri, N. A."

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    Pedological characterization of some typical alluvial soils of Kilombero District, Tanzania
    (American Journal of Agriculture and Forestry, 2017-03-02) Kalala, A. M.; Msanya, B. M.; Amuri, N. A.; Semoka, J. M.
    This study was carried out in Kilombero District, Tanzania with the objective of characterizing the soils in terms of their morphology, genesis, physico-chemical properties and classification. Three pedons KISA-P1, MKU-P1 and MBA-P1 were identified within the Kilombero Valley, dug, described and sampled. Disturbed and undisturbed soil samples were taken from designated pedogenic horizons for physical and chemical analysis in the laboratory. Using both field and laboratory data soils were classified using both USDA Soil Taxonomy and World Reference Base for Soil Resources schemes of classification. Results show that the three pedons were developed under Isohyperthemic temperature and Aquic moisture regimes. All pedons were deep (100 - 120 cm). Whereas Pedons KISA-P1 and MBA-P1 had sandy clay loam topsoils overlying sandy clay subsoils, Pedon MKU-P1 had clayey texture throughout its profile depth. All pedons had low chromas of . 3 and redoximorphic features in form of abundant mottles particularly in the subsoils. Topsoils of Pedons KISA-P1 and MBA-P1 had dominantly friable to very friable moist consistence while those of Pedon MKU-P1 had very firm moist consistence. Subsoil moist consistence varied from firm to extremely firm (Pedons KISA-P1 and MKU-P1) and from friable to very firm (Pedon MBA-P1). Structures were dominantly weak to moderate subangular blocky in all studied soils but some horizons were structureless single grained and massive. Soil reaction ranged from extremely acid (topsoil of MBA-P1) to mildly alkaline (subsoil of MKU-P1) with pH values of 4.44 and 6.73 respectively. Topsoil organic carbon and total nitrogen contents in the studied pedons were low (0.66 to 1.4%) and very low to low (0.08 to 0.19%) respectively. CECsoil values were rated as low to medium ranging from 8.4 to 23.8 cmol (+)/kg respectively in Pedon KISA-P1 and Pedon MKU-P1. Percent BS values varied between and within studied pedons and ranged from low < 50% to high > 50%. Studied soils manifested nutrient imbalances in respect of basic cations. On the overall, fertility of the studied soils was rated as low to medium. According to USDA Keys to Soil Taxonomy, Pedons KISA-P1 and MKU-P1 classified as Inceptisols, equivalent to Cambisols in WRB for Soil Resources whereas Pedon MBA-P1 classified as Entisols equivalent to Fluvisols. All three sites were recommended for paddy production.
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    Sulphur and zinc fertilization effects on growth and yield response of rice
    (International Journal of Plant & Soil Science, 2016-06-03) Kalala, A. M; Amuri, N. A.; Semoka, J. M. R.
    Information on critical concentration and optimum rates of fertilizers is very important in the correction of sulphur (S) and zinc (Zn) deficiencies. A study was carried in the screen house experiments to establish optimum rates and critical concentrations of sulphur and zinc in both soil and rice shoots using soils of Kilombero district, Tanzania. Two experiments were conducted, one with varied levels of S and the other with varied levels of Zn. The treatments were absolute control for both experiments, three levels of S namely 0, 20 and 40 mg kg -1 soil and three levels of Zn -1 namely 0, 5 and 10 mg kg soil. Rice (variety SARO-5) was grown in pots arranged in a randomized complete block design with three replications. The results indicated that soil critical concentration of S was 10.0 mg kg -1 and the S critical range in rice shoots was 0.18 to 0.25%. -1 Established critical level of soil Zn was 1.4 mg kg while the Zn shoots critical concentration was 22 -1 mg kg . Grain yield was significantly increased for plants grown in eight and three out of ten soils -1 tested due to an application of S and Zn, respectively. Rates of 20 mg S and 5 mg Zn kg soil were optimum rates for soils with low S and Zn, respectively. The results indicated that 17 and 6 out of 19 studied soils of Kilombero had S and Zn concentration below the critical level, respectively. It was concluded that sulphur deficiency was widely spread and its application and management is crucial, while Zn deficiency was an emerging problem in the paddy soils of Kilombero valley.