RA 00110.pdf - OAR@ICRISAT
RA 00110.pdf - OAR@ICRISAT
RA 00110.pdf - OAR@ICRISAT
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Table 1. Percentage of cultivated area sown to major crops, as sole crop or in a crop mixture, in three agroclimatic zones of<br />
Burkina Faso, I C R I S A T survey results, 1981.<br />
Zone<br />
Sahel<br />
Sudan<br />
savanna<br />
Northern Guinea<br />
savanna<br />
Crop<br />
Sole<br />
Mixture<br />
Sole<br />
Mixture<br />
Sole<br />
Mixture<br />
Millet<br />
White sorghum<br />
Red sorghum<br />
Maize<br />
Groundnut<br />
Earthpea<br />
Cowpea<br />
Cotton<br />
Other<br />
92<br />
4<br />
-<br />
1<br />
1<br />
-<br />
0<br />
-<br />
1<br />
0<br />
-<br />
-<br />
1<br />
1<br />
-<br />
42<br />
-<br />
1<br />
27<br />
53<br />
4<br />
2<br />
9<br />
2<br />
0<br />
1<br />
2<br />
-1<br />
-<br />
1<br />
-<br />
-<br />
-<br />
60<br />
0<br />
0<br />
13<br />
31<br />
15<br />
4<br />
4<br />
-<br />
0<br />
30<br />
2<br />
0<br />
2<br />
2<br />
12<br />
5<br />
2<br />
20<br />
1<br />
0<br />
1. - = Less than 0.5%.<br />
and 15% in the northern Guinea savanna zones.<br />
Millet is replaced principally by sorghum, which<br />
rises from about 5% in the Sahel to 60% in the Sudan<br />
savanna (the transition zone between millet and<br />
sorghum), and to 45% in the northern Guinean<br />
savanna, where sorghum is a competitive crop with<br />
cotton on similar soil types.<br />
Approximately 60% of the millet area is sown as<br />
an intercrop, most frequently with cowpea as the<br />
secondary component. Cowpea density generally<br />
varies from 1000-5000 plants ha -1 , and millet from<br />
10 000-30 000 plants ha -1 . The intercropping frequency<br />
increases in more arid zones, but with a<br />
decline in the densities of both components. Intercropping<br />
is more important among limited-resource<br />
farmers who are not equipped with animal traction<br />
equipment (as in approximately 85% of the farm<br />
units in Burkina Faso).<br />
Research conducted by the ICRISAT Agronomy<br />
Program in Burkina Faso, has found that although a<br />
cowpea intercrop generally has little effect on millet<br />
grain yields, increased millet density can severely<br />
reduce cowpea grain yields (Stoop 1984a). Whether<br />
there are important differences among millet cultivars<br />
competing with cowpea has not been examined,<br />
but such research on sorghum cultivars has found<br />
highly significant differences among cultivars (Stoop<br />
1984a). If similar differences exist for millet, then<br />
compatibility with a cowpea intercrop would be an<br />
important selection criteria in millet improvement<br />
programs, especially those targeted at limited-resource<br />
farmers in the Sahel and Sudan savanna.<br />
Land Use Patterns<br />
The highly diverse cropping patterns of W A S A T<br />
farmers reflect not only their objective of producing<br />
a varied diet, but also their strategy to exploit soil<br />
microvariability and to reduce risk. Farmers lack the<br />
means to modify land quality by intensive use of<br />
purchased inputs, deep plowing, or irrigation. However,<br />
they match land types to crop requirements to<br />
maximize aggregate productivity and to lower the<br />
risk of year-to-year production variability. Millet is<br />
important in satisfying both these objectives.<br />
Soil microvariability is principally related to distance<br />
from habitation points and toposequence<br />
position. Studies in Burkina Faso (Prudencio 1983)<br />
and elsewhere in West Africa (Norman et al. 1981)<br />
have found that, because of high transport costs,<br />
manure and other organic wastes are concentrated<br />
around habitation points, and their use declines<br />
rapidly with distance from dwellings. Farmers exploit<br />
this fertility gradient by planting crops which they<br />
consider to be the most responsive to enhanced soil<br />
fertility within an intensively cultivated inner management<br />
ring, while planting less responsive crops<br />
on fields at greater distances. Maize and red sorghum<br />
are the crops most frequently concentrated within<br />
the inner management ring, while millet is most<br />
commonly sown on those distant fields which are<br />
least frequently manured (Prudencio 1983).<br />
Exceptions to these general land-use patterns are<br />
imposed by soil quality differences linked to toposequence<br />
position. Fields located on upper slopes tend<br />
235