1994 Volume 3 Issue 1 Pages 3-17
Fertile soils and ample water cycling sustain human life on the earth. The distribution of fertile soils, and hence the distribution of population, are related to the amount and quality of geological fertilization processes. The geological fertilizations are 1) transport and sedimentation of eroded soils by river water, 2) volcanic activities to supply fresh easily weatherable volcanic ashes. 3) formation and transport of aeolian dust, and 4) dynamic balance between soil erosion and soil formation. Major soils in tropical Asia are generally active and fertile. In addition to favorable soil distribution, Sawah based rice agriculture using lowland Inceptisols is common. In the sawah agriculture the 1st. geological fertilization process is strengthened artificially. Major soils of tropical Africa are non productive Oxisols. Aridisols and Psamments which occupy 65% of total area. Major soils for agricultural production are Alfisols and Ultisols, which are suffering either water shortage or nutrients depletion. If we consider the such soil characters. the effective population density of Africa become 150 persons/km2, which is a similar level of that of tropical Asia. The effective population density of tropical America was 50 persons/km2. Past twenty years agricultural productivities were doubled in tropical Asia, whereas. although the population density doubled, the agricultural productivities have been stagnated in tropical Africa. Soil degradations and desertifications are accelerating. Why has the green revolution not yet realized in Africa despite the successful experience in tropical Asia. The author hypothesizes that the key issue is general underdevelopment of lowland agriculture in tropical Africa. The “environment creative technology”, such as sawah farming is lacking in sub-Sahara Africa. Therefore irrigation was not efficient and thus development was slow, which made it difficult to use fertilizer efficiently, and accordingly high yielding varieties were useless. The sawah based farming is an intensive and sustainable system. Sustainable roductivity of 1 ha of sawah may be equivalent to more than 10 ha of upland field. If we can expand the sawah based farming in tropical Africa we will be able to alleviate present crises of environment and agriculture in tropical Africa. Therefore the cooperation between tropical Asia and tropical Africa will be important not only for sustainable development of agriculture but also for creating our new global societies.
