APPENDIX IX

CROP SUITABILITY OF WATER COLLECTING SITES

Short-term dryland crops I

This group includes some short duration crops (wheat, barley, rye, dryland rice, foxtail millet, chickpea, rape, and forage legumes which are somewhat tolerant to excess moisture. For LGPs less than 30 days it is assumed there is on the average insufficient water to bring these crops to maturation and yield, especially since the contribution from rainfall is also almost non-existent. At LGPs longer than 120 days these crops will grow irrespective additional water. It has been assumed that the Fluvisols are too wet in LGPs over 300 days. Most of these crops are marginal to not suitable in humid areas. Agro-climatic constraints alone will render these long LGPs already marginal to not suitable.

Suitability class | Percentage of water-collecting sites suitable per LGP class
0 | 1- 29 | 30-59 | 60-89 | 90-119 | 120-149 | 150-179 | 180-209 | 210-239 | 240-269 | 270-299 | 300-329 | 330-364 | 365- | 365+
VS |  |  |  |  |  | 33 | 33 | 33 | 33 | 33 | 33 |  |  |  |
S |  |  |  |  | 33 |  |  |  |  |  |  |  |  |  |
MS |  |  |  | 33 |  | 33 | 33 | 33 | 33 | 33 | 33 |  |  |  |
mS |  |  | 33 |  | 33 |  |  |  |  |  |  |  |  |  |
NS | 100 | 100 | 67 | 67 | 34 | 34 | 34 | 34 | 34 | 34 | 34 | 100 | 100 | 100 | 100

Short-term dryland crops II

The crops in this group (sorghum, pearl millet, cowpea) have either a shorter duration than Group I (pearl millet and cowpea) or tolerance to both drought as well as to excess water (sorghum). Therefore for some parts of the Fluvisols in 1-29 days growing periods some modest yield may be expected (though not in all years). At the wet end of the LGPs these crops are treated similarly to Group I.

Suitability class | Percentage of water-collecting sites suitable per LGP class
0 | 1- 29 | 30-59 | 60-89 | 90-119 | 120-149 | 150-179 | 180-209 | 210-239 | 240-269 | 270-299 | 300-329 | 330-364 | 365- | 365+
VS |  |  |  |  | 33 | 33 | 33 | 33 | 33 | 33 | 33 |  |  |  |
S |  |  |  | 33 |  |  |  |  |  |  |  |  |  |  |
MS |  |  | 33 |  | 33 | 33 | 33 | 33 | 33 | 33 | 33 |  |  |  |
mS |  | 33 |  | 33 |  |  |  |  |  |  |  |  |  |  |
NS | 100 | 67 | 67 | 34 | 34 | 34 | 34 | 34 | 34 | 34 | 34 | 100 | 100 | 100 | 100

Short-term dryland crops III

The crops in Group III include maize, phaseolus bean, soybean, and sunflower. They are more sensitive to excess water (especially water-logging) than Group I and II crops. Therefore, they are not considered to be suitable in areas where LGP exceeds 270 days. Their water requirements are similar or somewhat higher than Group I crops.

Suitability class | Percentage of water-collecting sites suitable per LGP class
0 | 1- 29 | 30-59 | 60-89 | 90-119 | 120-149 | 150-179 | 180-209 | 210-239 | 240-269 | 270-299 | 300-329 | 330-364 | 365- | 365+
VS |  |  |  |  |  | 33 | 33 | 33 | 33 |  |  |  |  |  |
S |  |  |  |  | 33 |  |  |  |  |  |  |  |  |  |
MS |  |  |  | 33 |  | 33 | 33 | 33 | 33 | 33 |  |  |  |  |
mS |  |  | 33 |  | 33 |  |  |  |  |  |  |  |  |  |
NS | 100 | 100 | 67 | 67 | 34 | 34 | 34 | 34 | 34 | 67 | 100 | 100 | 100 | 100 | 100

Short-term dryland crops IV

Root crops (white potato, sweet potato, sugarbeet) are all sensitive to high groundwater levels and water-logging. Cotton and groundnut are also very sensitive to excess moisture. These crops can only be grown on the rarely flooded parts of the Fluvisols, provided they are well drained. Apart from groundnut the growth cycles of the crops in this group are slightly longer than the crops in Group I-III. This makes crops in Group IV slightly more vulnerable.

Suitability class | Percentage of water-collecting sites suitable per LGP class
0 | 1- 29 | 30-59 | 60-89 | 90-119 | 120-149 | 150-179 | 180-209 | 210-239 | 240-269 | 270-299 | 300-329 | 330-364 | 365- | 365+
VS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
S |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
MS |  |  |  |  |  | 33 | 33 | 33 | 33 |  |  |  |  |  |
mS |  |  |  |  | 33 | 33 | 33 | 33 | 33 | 33 |  |  |  |  |
NS | 100 | 100 | 100 | 100 | 67 | 34 | 34 | 34 | 34 | 67 | 100 | 100 | 100 | 100 | 100

Wetland rice

Wetland Rice is difficult to grow under rainfed conditions. In particular the water management is problematic. Yields obtained from purely rainfed paddy is generally low. 2-3 t/ha is already good. Flood water supply comes in the semiarid areas in an erratic fashion; too little too late or too much too soon. In the sub-humid and humid areas the flood hazard makes management difficult (submerging and flood damage by flowing water). LGPs less than 150 days have been considered insufficient to obtain yield. Very long LGPs are assumed to be associated with high flood risks (submerging, flowing water, high water levels during maturing and harvest).

Suitability class | Percentage of water-collecting sites suitable per LGP class
0 | 1- 29 | 30-59 | 60-89 | 90-119 | 120-149 | 150-179 | 180-209 | 210-239 | 240-269 | 270-299 | 300-329 | 330-364 | 365- | 365+
VS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
S |  |  |  |  |  |  |  | 33 | 33 | 33 |  |  |  |  |
MS |  |  |  |  |  |  | 33 |  |  |  | 33 | 33 | 33 |  |
mS |  |  |  |  |  | 33 |  |  |  |  |  |  |  | 33 |
NS | 100 | 100 | 100 | 100 | 100 | 67 | 67 | 67 | 67 | 67 | 67 | 67 | 67 | 67 | 100

Cassava

Cassava is preferably not grown on Fluvisols because of its sensitivity for excessive wetness in the soil. On the higher parts of Fluvisols short duration cassava can be found (e.g., LGP of 180-270 days in Ghana). Since cassava is not really benefiting from extra moisture, the best LGPs are those where also rainfed cassava would do reasonably well. Towards the wetter end of the LGPs (more than 240-270 days) cassava is not anymore to be considered on Fluvisols.

Suitability class | Percentage of water-collecting sites suitable per LGP class
0 | 1- 29 | 30-59 | 60-89 | 90-119 | 120-149 | 150-179 | 180-209 | 210-239 | 240-269 | 270-299 | 300-329 | 330-364 | 365- | 365+
VS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
S |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
MS |  |  |  |  |  |  |  | 33 | 33 |  |  |  |  |  |
mS |  |  |  |  |  |  | 33 |  |  | 33 |  |  |  |  |
NS | 100 | 100 | 100 | 100 | 100 | 100 | 67 | 67 | 67 | 67 | 100 | 100 | 100 | 100 | 100

Sugarcane

Sugarcane is fairly tolerant to flooding and water-logging (e.g., see FAO, 1988). The water from rainfall and whatever comes from the Fluvisols must meet full crop water requirements for 8 to 9 months. It is assumed that the contribution through additional water from Fluvisols sufficiently extends the growing period starting from LGP 180- 210 days onwards. At harvest presence of excess moisture is less favorable for both yield and management of the crop. There need be a predictable period during which the Fluvisol environment provides at least 2 months of dryer conditions.

Suitability class | Percentage of water-collecting sites suitable per LGP class
0 | 1- 29 | 30-59 | 60-89 | 90-119 | 120-149 | 150-179 | 180-209 | 210-239 | 240-269 | 270-299 | 300-329 | 330-364 | 365- | 365+
VS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
S |  |  |  |  |  |  |  |  |  | 33 | 33 |  |  |  |
MS |  |  |  |  |  |  |  |  | 33 |  |  | 33 |  |  |
mS |  |  |  |  |  |  |  | 33 |  |  |  |  |  |  |
NS | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 67 | 67 | 67 | 67 | 67 | 100 | 100 | 100

Banana/plantain, oil palm

Banana/plantain and oil palm prefer humid conditions. Banana is somewhat tolerant to water-logging, oil palm somewhat less. High groundwater tables are not tolerated. Both perennials require at least eight months during which full water requirements are met. Fluvisols occurring in LGPs of more than 300 days are assumed to be associated with longer periods with high groundwater levels and are therefore unsuited for oil palm and banana/plantain.

Suitability class | Percentage of water-collecting sites suitable per LGP class
0 | 1- 29 | 30-59 | 60-89 | 90-119 | 120-149 | 150-179 | 180-209 | 210-239 | 240-269 | 270-299 | 300-329 | 330-364 | 365- | 365+
VS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
S |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
MS |  |  |  |  |  |  |  | 33 | 33 | 33 |  |  |  |  |
mS |  |  |  |  |  |  | 33 |  |  |  | 33 |  |  |  |
NS | 100 | 100 | 100 | 100 | 100 | 100 | 67 | 67 | 67 | 67 | 67 | 100 | 100 | 100 | 100

Olives

Olives tolerate neither high groundwater tables nor water-logging and flooding or inundation. Therefore, olives are not considered for cultivation on Fluvisols.

Suitability class | Percentage of water-collecting sites suitable per LGP class
0 | 1- 29 | 30-59 | 60-89 | 90-119 | 120-149 | 150-179 | 180-209 | 210-239 | 240-269 | 270-299 | 300-329 | 330-364 | 365- | 365+
VS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
S |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
MS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
mS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
NS | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100

Pastures

Natural pastures are well adapted to wet conditions. Normally the species mix is fine-tuned to the environmental conditions. Artificial (sown) pastures might grow unevenly on Fluvisols depending on both local differences of soil fertility and water supply. The total period of water availability on Fluvisols can be considered an adequate measure of the productivity regarding pastures (of course, periods of water-logging, flooding and inundation are to be subtracted).

Suitability class | Percentage of water-collecting sites suitable per LGP class
0 | 1- 29 | 30-59 | 60-89 | 90-119 | 120-149 | 150-179 | 180-209 | 210-239 | 240-269 | 270-299 | 300-329 | 330-364 | 365- | 365+
VS |  |  |  |  |  | 33 | 33 | 33 | 67 | 67 | 67 | 33 |  |  |
S |  |  |  | 33 | 33 |  | 33 | 33 | 33 | 33 | 33 |  | 33 |  |
MS |  |  | 33 |  | 33 | 33 |  | 34 |  |  |  | 33 |  | 33 |
mS |  | 33 |  | 33 |  |  | 34 |  |  |  |  |  | 33 | 33 | 33
NS | 100 | 67 | 67 | 34 | 34 | 34 |  |  |  |  |  | 34 | 34 | 34 | 67