486 
MAPSYMBOL 
DESCRIPTION OF PHYSIOGRAPHY 
SOIL CLASSIFICATION 
A 
Deep poorly drained heavy soils on level 
plain with recent alluvial deposits. 
flat flood 
1. 
2. 
3. 
Utric Fluvisols 
Utric Gley sols 
Pellic vertisols 
C 
Deep excessively drained sands, sands to sandy lo 
ams over sandy clayson level to gently undulating 
coastal plain. 
1. 
2. 
3. 
4. 
Albic Arenosols 
Cambie 'Arenosols 
Othic Luvisols 
Eutrigle sols 
soil properties considered in describing 
the profiles. In this survey the level of 
mapping the area was limited only to main 
land type. 
2.5 Map compillation and Field work 
During field work, location of pits and 
observation on mapping Unit, boundaries 
were marked on 1:100,000 topographical map. 
Field surveying traverses were made along 
the farm boundary and across the farm area. 
Nearly, all profile pits were dug to depths 
of 150cm in order to check the ground water 
table and the soil parent material. Each 
horizon in a profile was examined for the 
study of soil development. The major pa 
rameters commonly looked for in the profile 
are depth of individual horizon, colour 
(dry and moist), texture, structure, consi 
stency porosity, parent material, presence/ 
absence of roots and fauna, presence of 
carbonates, concretions and cracks. pH, 
Conductivity, texture were measured separa 
tely in the laboratory together with other 
chemical analyses. Colour notations were 
referred to the Munsel Coloiir Chart (Soil 
Test inc. USA, 1971 Edition). Profile 
pits were described using (Guidelines for Soil 
Profile Pescription - FA0) and soil samples 
were sent to the Laboratory for some physi 
cal and chemical analyses. The final soil 
map was produced at a scale of 1:10,000 
as proposed by the client to facilitate 
farm planning and land use purposes. 
Due to field obstacles earlier observed 
during the reconnaisance field trip, soil 
observations at the far southern parts of 
the project area on the alluvial plain, 
were not made. Soils in these parts were 
extrapolated from aerial photo-interpre 
tation and the physiographical map. Nor 
mally the alluvial plain area, consists 
of poorly drained heavy clay soils subje 
cted to frequent flooding by river over 
flow’s of the Ruvu River, whereas the Coa 
stal Plain soils range from deep excessi 
vely drained sands to sandy clay loams. 
3. SOIL CLASSIFICATION AND MAPPING 
3.1 Soil Laboratory data and results 
1. pH and Ec were determined by using 
the 1:5 soil to water ratio method. 
2. Particle size analysis was carried 
out using the hydrometer. 
3» Available phosphorus was determined 
by using the Dickman and Bray 1 method. 
4. Exchangeable cations Na, K, Ca, Mg, 
were determined by leaching the soils in 
Ammonium Acetate extracting solution IN. 
5. Organic carbon % was determined by 
using the Walkley and Black method. 
6. Available Nitrogen % was determined 
using the Alkaline permanganate method. 
7. C.E.C. was not determined but was 
approvimated by adding the total of bases. 
3.2. Results 
1. From soil analytical data the soils 
in the area are non-saline. However the 
subsoils have an increased amount of solu 
ble salts. In general the pH of the soils 
indicate that the soils are acidic. It 
will be necessary to raise the pH to about 
7.0 as the pH common to most plants is 6-8. 
SCALE 1:500,000. 
MI 
QUATERNARY. 
Coastal plain deposits reworked clays 
silts, sands and rare grovels 
QUANTERNARY 
Alluvial deposits (clays, silts, sands and 
rare gravels.) 
NEOGENS (MIOCENE PLIOCENE) 
Undifterentated sedimentary deposits interbecfded .sandy 
c * :y , and clayey sands ¿ravel scattered thoughoul in a 
clay matrix 
Cretaceous 
thin 
san d stones 
sandy limestones and shales 
Figure 3 Geology* of the farm area