PedologicalCharacterization and Fertility Assessment of Mbimba Substation Soils Under Coffee Production in Mbozi District, Tanzania

Abstract

Pedological characterization was carried out on the soils of Mbimba Mbozi, Tanzania. A representative soil profile (TaCRI-P1) was identified, excavated and described using FAO (2006) Guidelines. Four disturbed soil samples and three undisturbed core samples were taken from the profile horizons for Physico-chemical laboratory analysis. The pedon developed under udic moisture and thermic temperature regimes were very deep (> 150 cm), well-drained and had dark brown to black topsoil colour over dark brown to dark reddish subsoil colour. Soil texture ranged from clay loam to clay. Soil pH was rated as very strong acid to medium (4.73 - 5.98) for all horizons. Organic carbon was low to medium; N was very low to low; CEC was medium to high and exchangeable bases ranged from low to high. Bulk densities were high (2.24 - 2.44 g/cc) for topsoil and low (0.33 - 0.91) for subsoil. Soil moisture retention properties indicated that surface horizon (0 - 5 cm) retained more water followed by intermediate (45 - 50 cm) horizon and the subsoil (95 - 100 cm) respectively. According to USDA Soil Taxonomy and World Reference Base for Soil Resources, the pedon at Mbimba was classified as Typic Palehumults and as Haplic Alisols, respectively. These taxa reflected properties that may guide on the use and management of soils.  Before lime application, the upper two horizons of the pedon had total nitrogen level ranging between 0.04 - 0.17%, Phosphorus 2.91 - 4.59 mgkg^-1_, Potassium 2.36 - 1%, Calcium 2.36 - 2.35 cmol(+)kg^-1 and Magnesium 0.71 - 1.93 cmol(+)kg^-1 which were low to medium. Thus, application of inorganic (N, P, K - rich), Ca+Mg and organic fertilizers is recommended to increase nutrient availability. Use of CaMg(CO₃)₂ as soil amendment should be taken into consideration to raise soil pH and enhance balanced nutrient availability for coffee growth.