SOIL SURFACE CHARACTERISTICS AND VARIABILITY IN THE GROWTH OF MILLET IN THE PLATEAU AND VALLEY REGION OF WESTERN NIGER

Short-range (less than 10 m) spatial variability in crop growth in the Sahelian zone of West Africa is a common occurrence. This phenomenon has been attributed to variability in soil chemical and physical prope rties, which are influenced by the effects of wind and water erosion a nd can be associated with micro-topographic features of the landscape. This study was conducted to quantify the association of variability i n the growth of local millet (Pennisetum glaucum (L) R.Br.) with soil surface characteristics that can be easily evaluated. Millet yield and soil characteristics were measured in transects throughout farmers fi elds within a 500 ha experimental watershed located in the plateau and valley geomorphic unit in Western Niger. Best millet growth was assoc iated with micro-topographic high positions within the landscape, whic h comprised 30% of the surface area planted to millet. The worst growt h was associated with eroded soils (10% of the surface area). Micro-to pographic highs were associated with the growth of a tree species, pri marily Guiera senegalensis, Combretum glutinosum or Piliostigma reticu latum, which are the predominant species of the savanna in this ecolog ical zone.