In the case study of the field research conducted by authors in Ghana, 1991, it was presumed that the very short fallow period due to socio-economic situations of large population and tenant problem would cause fast circulation of shifting lands and this fact means severe decreasing forest and fertile fields. Therefore, sustainable agriculture with flexibility should exist to support their increased population in those difficult regions instead of extending arable lands by burning.
In the tropical region where the farmers manage the fields of small size of area intensively, the multiple cropping system would be useful and effective to insure the safety of yields.
Intercropping or mixed cropping method requires usually much labour to grow plants due to more than two crop species at the same field, nevertheless, so far, these techniques have been adopted among many farmers because of those rational advantages in farm management.
Some of these attractive merits come from the characteristics of the complicated planting patterns with decreasing damage of crops by insects or fungi attack and preventing soil erosion of the fields from heavy rain, strong wind and drought.
One of the newly noticeable intercropping might be the combination of cereals and perennial leguminous plants from the view of low input energy, which could be regarded as the category of agro-forest system.
By certain strip type of planting there is a possibility of realization of mechanical management, if the crop combination is proper and acceptable in an easy way, and this mechanization management will be valid in developed countries, too.
