and ecological environment. Long bush fallow periods were
effective in restoring soil fertility for the prevailing level of crop
yields and intensity of cropping. Pressure on land has resulted in
drastic reduction of the fallow periods and in some countries they
have disappeared completely. Intensive land cultivation with low
use of inputs due to the farmers’ inability to purchase what is
necessary has set in. This leads to nutrient ‘‘mining of the soils’’
which is manifested in degraded soils and reduced crop yields.