Table 2. Characteristics of the Agro-Ecological zones 
Zone 16 
Zone 8 
Zone 14 
Zone 4 
Zone 3 
climate (KC3PPEN classi 
fication) 
BSwh 
(dry hot steppe climate) 
Cwa (some Cwb) 
(warm temperate with hot 
(warm) summers) 
Cwa and Cwb 
(warm temperate with 
hot / warm summers) 
Cwb 
(warm temperate with 
warm summers) 
Cwb 
(warm temperate with 
warm summers) 
Dominant altitude (m.a.s.l.) 
Less than 1000 
1100 - 1700 
1600 - 2000 
800 - 1600 
1600 - 2800 
Mean annual rainfall (mm) 
550 - 600 
600 - 900 
900 - 950 
1100 - 1300 
1200 - 1600 
physiographic charac 
teristics 
Flat to slightly undu 
lating pediplains with 
some alluvium and sub 
parallel drainage pat 
tern; rocky hills 
Highland pediplains 
with inselbergs and 
some periodically swampy 
depressions; rocky 
mountains and hills 
Undulating highland pla 
teaus with numerous pe 
rennially swampy drain 
age lines (bottomlands) 
and depressions 
Rolling to hilly with 
deep valleys in the 
south; undulating to 
rolling upland plateau 
in the north 
Hills, mountains and 
undulating highland 
plateaus 
Dominant vegetation / 
land use 
Open Acacia-thornbush / 
grazing; annual crops 
on alluvium 
Miombo, Commiphora, 
Combretum / annual crops 
(maize, tobacco), 
grazing 
Wooded grassland with 
miombo, Parinari and 
Uapaka species / graz 
ing, some cultivation 
(maize), pine affores 
tation 
Miombo woodland, grass 
land / grazing, culti 
vation (tea, maize), 
wattle plantations 
Grassland, forest rem 
nants / grazing, culti 
vation (maize, wheat, 
potatoes, tea, pyre- 
thrum), wattle planta- 
tations 
Dominant soils 
Well-drained dark to 
yellow-brown loams, 
dark cracking clays, 
red loams; mos soils 
saline 
Well-drained moderately 
leached red clays and 
loams, yellow sands and 
loams, some dark crack 
ing clay 
Well-drained, highly 
leached yellow clay 
(partly with dark top 
soil), poorly drained 
clays in bottomlands 
and depressions 
Well-drained moderately 
and highly leached red 
clay (often with humic 
topsoil) 
Well-drained highly 
leached red clay 
(often with humic top 
soil), locally soils 
derived from volcanic 
ash 
hills: rock and very 
shallow soils 
hills: rock and very 
shallow soils 
Hills: rock and very 
shallow soils 
Hills and ridges: 
rock and very shallow 
soils 
Hills and ridges: 
rock and very shallow 
soils (partly with co 
vering of volcanic ash) 
many inselbergs and some scattered periodically 
flooded depressions. Another great part of the zone 
consists of rocky hills and mountains. A large por 
tion of the pediplains is cultivated, mainly with 
maize. The hills are covered by miombo woodland. 
The main soils are moderately leached red clay 
and loam, yellow to yellow brown sand and loam and 
some scattered patches of dark cracking clay. The 
footslopes around the inselbergs are often strongly 
affected by gully erosion. Some other areas are se 
verely degraded by sheet erosion. 
In this zone the information obtained from the 
satellite imagery and those from the aerial photo 
graphs completed each other ideally. The spectral 
reflectance characteristics of the soil surface 
were again the dominant mapping support. Therefore 
most boundaries were mapped from the satellite ima 
gery. As in Zone 16, the IHS image allowed a much 
better colour differentiation than the FCC (compare 
Figure 2). 
The synoptic view of large areas with the help of 
the satellite imagery was especially useful to de 
lineate extensive complex mapping units with asso 
ciations of several soils. These units have very 
gradual boundaries which could only be delineated 
on the basis of a change in the general colour pat 
tern. 
The aerial photographs were mainly utilized to 
map erosion gullies which are not visible on any of 
the two types of satellite imagery. Some relief-de 
pendent soil boundaries (e.g. river terraces) were 
also delineated on the aerial photographs as were 
small depressions and narrow floodplains. Due to 
the smaller scale these little features could hard 
ly or not at all be identified on the satellite 
imagery. Some of the soil boundaries which could be 
identified on the photos were too detailed for the 
scale of the survey. 
General mapping problems were caused by some 
burnt areas which appear on the satellite imagery 
very similar to areas of dark cracking clay. Dif 
ferentiation within the red soils posed another 
difficulty. Despite very important differences 
(e.g. soil depth, texture, degree of leaching, sto 
niness etc.) all red soils have the same or very 
similar reflectance characteristics. Thus they all 
give the same colour on the satellite images res 
pectively the same graytone on the aerial photo 
graphs . 
6.3 Zone 14 
With an annual rainfall of about 950 mm, Zone 14 
has an intermediate position between the low rain 
fall zones 16 and 8 and the high rainfall zones 4 
and 3. The greatest port of Zone 14 consists of an 
undulating highland plateau with straight, narrow, 
perennially swampy drainage lines ("bottomlands"). 
Typical features of this zone are several larger 
and smaller swamps and periodically swampy depres 
sions ("mbugas") often fringed by numerous alluvial 
fans. 
Most of the area is covered by grassland and 
wooded grassland. Some extensive areas are affor 
ested with pine species. 
The dominant soil of the zone is a deep highly 
leached yellow clay, in some higher areas with a 
humic topisoil. The depressions and alluvial fans 
are characterized by a variety of imperfectly and 
poorly drained soils. In the southwest of the zone 
some extensive areas with red and yellow sands oc 
cur. 
In Zone 14 the aerial photographs were the main 
mapping support. Most soil boundaries are relief- 
dependent and could excellently be mapped from the 
photos and even directly from the contour lines of 
the toposheets. 
The satellite imagery was useful to delineate the 
agro-ecological land units, but within these units 
neither of the two types of imagery showed much 
soil-related differentiation. In contrast to Zones 
16 and 8 not the soil colour but the vegetation / 
land use determines the reflectance characteristics 
of the area. Therefore most boundaries visible on 
the satellite imagery are related to land-use chan 
ges which showed very limited correlation with soil 
differences. Merely major bottomlands could easily 
be identified from the satellite imagery. 
6.4 Zone 4 and Zone 3 
With annual rainfalls of about 1200 mm (Zone 4) 
and about 1400 mm (Zone 3) both zones belong to the 
high rainfall area of the Iringa Region. Dense, 
fairly uniform vegetation covers of miombo wood 
land, grassland and forest remnants are typical for 
these two zones. The area shows considerable relief 
differences with elevations up to about 1800 metres 
in Zone 4 and 2900 metres in Zone 3.