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Abstract
Soils in a large part of Niger's agricultural area are sandy and very low in nitrogen (N),
phosphorus (P) and organic matter. This low soil fertility combined with low and erratic
rainfall constitutes a severe constraint on food cropping in the area. Although agronomists
have advised chemical fertilization as a means of improving soil fertility, little fertilizer has
been used in this area of the world.
The economic management of soil fertility in the agricultural area of Niger is analyzed
using a dynamic model of farmer decision-making under uncertainty. The model is based on
agronomic principles of plant growth and accounts for the carry over of P, an immobile
nutrient.
At current input prices, a soil P content of at least 14 ppm is found to be desirable. This
target is above the natural soil fertility level of about 3 ppm. It can be maintained with a
moderate annual application (12 kg P20 5 ha- 1) of simple superphosphate. Results also
suggests that returns to N fertilization are too low and variable to warrant the use of this
input.