Although the interview data of this study are variable, the chemical soil analyses shown in table 5
and described in detail in Hoffman et al. (2001) indicate that farmers in the Zamfara Reserve combine
crop planting patterns and the application of organic and mineral fertilisers in an effective way to maintain
the fertility of their soils. Intensive application of farmyard manure was found to be the most important
source of nutrients, followed by dung voided by livestock directly on the field. Nutrient transfer from the
rangeland to the cropland through takin gida application or corralled animals is an important factor for
maintaining soil fertility. However, productivity of the rangeland in the reserve is declining due to loss
of pasture for cropland encroachment and a shift in the vegetation composition towards less palatable
plant species. In the medium and long term, this might adversely affect the number and productivity
of livestock kept, and the productivity of the cropland supported by nutrient transfer. In the CSZs in
northern Nigeria, however, a positive correlation was found between human and livestock population
densities, based on an intensive crop - tree - livestock integration. The Zamfara Reserve seems to be
on a transition from an extensive, less integrated to an intensive, more integrated crop-livestock system.
Farmers use their own and pastoral livestock to manure their fields. Poor farmers cannot engage in
manure contracts due to their limited resources. Hence, soil fertility differences between farmers might
increase in the long run, aggravating the existing wealth differences.