These results indicated that the rainfall
and the amounts of chemical pesticides and herbicides
used were positively related to cassava yield.
Rainfall was a significant factor for both maize and
cassava production in all areas. However, the Cobb-
Douglas model has some limitations, since the model
does not take into account input interaction effects,
which affect somewhat the significance in yield. This
study assumed all other factors, besides rainmaking
services, were the same. In reality, there are other
factors that affect productivity, such as the quality
of land, types of chemical pesticides and herbicides
or fertilizer used, and farmer practice, but these were
not included in the model