Abstract:
This study was conducted in some selected soils of Morogoro (Magadu) and Mbeya
(Uyole) regions of Tanzania to classify and characterize their properties. Two
representative pedons (SUARAT-P1 and UYOLE-P1) were dug and described using FAO
guidelines clarifying morphological features, physico-chemical properties and genesis.
The representative pedons were geo-referenced using Global Positioning System (GPS)
receiver. A total of nine (9) genetic soil horizons were identified from both sites and
samples from each horizon collected for physical and chemical analyses. Soils from both
sites were very deep and topsoil moist colors ranged from hue of 7.5YR to 10YR with
chroma of less than 3 in SUARAT-P1 and UYOLE-P1 pedons. Soil structure ranged from
strong fine crumbs in topsoils to medium coarse sub-angular blocks in subsoils of
SUARAT-P1 while UYOLE-P1 had weak fine sub-angular blocks in topsoils and subsoils.
The SUARAT-P1 had sandy clay (SC) texture in topsoil and clay texture in subsoil while
UYOLE-P1 was sandy loam (SL) in topsoil and sand clay loam (SCL) in subsoil. Soil
reaction were slightly acid to very strongly acid in SUARAT-P1 (pH 6.54 - 4.46) whereas
UYOLE-P1 were slightly acid to neutral in the subsoil horizons (pH 6.35 – 7.32). Organic
carbon ranged from very low to low (0.12- 0.95%) in SUARAT-P1 from 0-23 cm and
medium (1.5%) from surface to 25 cm depth in UYOLE-P1. Nitrogen levels were very
low to low (0.05 - 0.12%) in both sites, whereas available P ranged from low (0.30 mg kg -
1
) to medium (8.55 mg kg -1 ) in both pedons. The figures for soil OC and N will be used as baseline to forecast SOC and N sequestration potential in selected study sites. CEC of
SUARAT-P1 was medium ranging from 12.4 to 23.2 cmol(c) kg -1 , whereas UYOLE-P1
was medium to high (15 – 34 cmol(c) kg -1 ). The figures for soil OC and N will be set as
baseline for SOC and N sequestration studies in the next chapters. In SUARAT-P1, topsoil
BS was high (> 50%) and low (< 50%) in the subsoil while UYOLE-P1 registered high
BS throughout its profile depth. As diagnostic horizons for soil classification, the
SUARAT-P1 had an ochric epipedon overlying a kandic horizon and classified according
to USDA Soil Taxonomy as Typic Kandiustults, while UYOLE-P1 had an ochric
epipedon over a cambic horizon and was named as Andic Dystrudepts corresponding
respectively to Haplic Lixisols and Eutric Andic Cambisols in the WRB for Soil
Resources. The results have indicated that, studied soils are less fertile with possible
reconstitution through land and crop management practices which include but not limited
to no-tilling or conservation tillage, manuring and proper fertilizer application; residue
retention, possible fallowing, liming for potential buffering of soil pH especially at
SUARAT-P1 and crop rotation and intercropping with leguminous crops.
