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The AEZ land inventory was prepared by overlaying the climatic and soil inventories. The two maps were superimposed to provide a key map which contains all the inherent data on climate, thermal regime, length-of-growing-period zones, soil associations, slope, phase and texture.
This map is the information base of the whole study. The information it contains then had to be processed by computer. A 10 x 10 km grid was placed on the land inventory, dividing the developing world up into some 650000 squares (an illustration of the result appears on the back cover). Researchers then counted, for each country, the number of squares that fell within the same climate, thermal regime, length of growing period and soil association.
This information was entered into the computer, and the composition rules for the soil associations were applied. For example, an association with a dominant soil, one associated soil and one inclusion is considered to be composed of 60 percent (by area) of the dominant soil, 30 percent of the associated soil and 10 percent of the included soil. In the most complicated case, where there is a dominant soil, three associated soils and four inclusions, each occupies 24, 20 and 4 percent of the area respectively.
This information enables the computer to calculate the areas of each soil unit in each soil association, by slope, texture and phase, as they occur in each climate and thermal regime and in each length-of-growing-period zone in each country.
The final stage of the computer program lists the total area of each soil unit, broken down by texture, slope and phase, in each climate, thermal regime and in each length-of-growing-period zone for each country (see diagram below). This is the data base for the AEZ study; it is used to provide the final estimates of the area of land suited for growing the 11 major crops in each country.
This data base can also be used to compute the total area of potentially cultivable land in each country. This is done by asking the computer to add the extents of land in each country that are suitable for growing one of the major crops. The results are shown on pages 32/33; of 99 countries studied, more than 20 are already cultivating as much land as is theoretically suitable for cultivation.
STEP 3
E: Final computer print- out
COUNTRY A |
MAJOR CLIMATE B |
and thermal |
regime |
n |
soil unit, slope, texture,
phase |
total extent (thousand ha) |
extent by LGP |
||
120-149 |
150-179 |
180-209 |
||
X a 2 |
144 |
22 |
54 |
68 |
X a 3 |
7 |
- |
3 |
4 |
X b 1 |
72 |
13 |
31 |
28 |
X b 2 |
144 |
22 |
54 |
68 |
Xh a 1 |
537 |
66 |
267 |
270 |
Xh a 1 |
lithic 67 |
7 |
35 |
25 |
Xh a 2 |
738 |
98 |
333 |
307 |
Xh a 2 |
lithic 66 |
7 |
35 |
24 |
Xh a 3 |
21 |
- |
10 |
11 |
Xh b 1 |
97 |
12 |
34 |
51 |
Xh b 1 |
lithic 67 |
7 |
35 |
25 |
The land inventory (C) is prepared by superimposing the climatic inventory (Al on the soil inventory (B). A 10 x 10 km (2-mm-square actual size) grid overlay is then placed over the land inventory (D). The area of each agro-ecological zone (areas with the same soil association, thermal regime and length of growing period) can men be counted. These data are computed, and the area of each soil unit is listed by slope texture, phase, climate, length of growing period and country (E).
A Climatic inventory includes information on three major climates, 14 thermal regimes and 21 growing period zones.
B Soil inventory includes information on soil associations, and associated slope, texture and phase.
C land inventory includes all me information contained in A and B.
D The 10-km grid overlay divides me developing regions into about 650000 squares, each containing detailed information on climate, growing period, soils and associated soil characteristics.
E Computer produces printout of me extent of each soil unit by slope, texture and phase, for each country by major climate, thermal regime and growing period.
