akinsanya, olawale - The Federal University of Agriculture, Abeokuta

and fertility management consideration only, but because of reduced labour for weed control.
Conservation @age, which includes minimum tillage or no tillage with incorporation or residue
mulch/cover cropping is an aspect of soil management that can guarantee sustainable crop production
in the tropics (Lal, 1997a; 1997b). Previously cultivated lands may not necessarily be degraded if
sustainable crop production practices were adopted.
2.3. CEREAL PRODUCTION IN THE TROPICS
Maize (Zea mays, L.) thrives well in the tropics but its production can be boosted further by provision of
nutrients and appropriate soil management practices in a given environment. According to David and
Adam (1985), maize is one of the world most important cereal crops. Maize is usually grown on wellstructured
soils of intermediate texture (sandy loams to loams). Maize can be cultivated by conventional
tillage, minimum tillage or zero tillage. Farmers are intensively using land for continuous cultivation with
none or few input. So in the tropics, particularly Africa, it is important to evaluate the changes in soil
properties as a result of continuous cultivation of the land.
Rice (Oryza'sativa) is very important as a staple food and an economic crop in many countries. It is both
indigenous and exotic crop in Africa. Rice production is concentrated in Asia where more than 90% of
the world supply is concentrated (FAO, 1981). Farmers cultivate rice in Africa mostly by depending on
the natural rise and fall of streams and shallows swamps to flood the crop, and in the upland on rainfall
to provide with ad~quate moisture.