chemical inputs, to meet the ever increasing need for food,
animal feed, fibre, and fuelwood has already resulted
in accelerated land degradation and loss of soil productivity
(Stoorvogel et al., 1993; Tolba, 1993).
Despite many decades of research on the intensification
of agriculture on rainfed uplands in the humid
and subhumid tropics, efforts to develop alternative,
sustainable and more productive food crop production
systems have thus far had only limited success
(Kang et al., 1991).
Traditional rainfed upland farming in the tropics
is mainly practised in areas dominated by either high
base status Alfisols or acid and low base status
Oxisols and Ultisols. All are fragile soils with moderate
to very low fertility status. Results of many
years of research have shown that the following
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