Sawah Hypothesis for Green Revolution in West Africa.
Toshiyuki Wakatsuki, Faculty of Agriculture, Kinki Univ, 2-3-22 Tomio, Nara, 631-8505, Japan, Moro M. Buri, Soil Research Insititute, Kwadaso, Kumasi, Ghana, and Oluwarotimi O. Fashola, International Institute of Tropical Agriculture, Ibadan, Nigeria.
The green revolution has yet occurred in West Africa (WA) and Sub Sahara Africa. During 1970-2003, although rice production increased from 2.4 to 7.7 million tons, yield has been stagnated at 1.3-1.7 t/ha. Numerous availabe lowland high yielding varieties (HYV) under Sawah system with good management could yield up to 6 tons per ha. But these potentials are never achieved on farmers' field because of poor water control and bad soil management systems. This acceralated soil, forest and land degradation in WA. This is why a renewed call for a concerted effort needs to be made for a better water and soil management systems referred to in this repoprt as Sawah System and right policy on rice development. Although lowland soils fertility and hydrological conditions are not ideal for Sawah development, since the agro-ecological conditions are quite similar to those of north-eastern Thailand, where is one of the rice center in the country, the potential area of Sawah based rice farming is enormous in WA. Ten to twenty million ha of sawah can produce additional food for more than 300 million people in future. The sawah based rice farming can overcome such soil fertility problems through the enhancement of the geological fertilization process, conserving water resources, and the high performance multi-functionality of the sawah type wetlands. The term sawah, Malayo-Indonesian origin, refers to leveled and bunded rice fields with inlet and outlet connecting irrigation and drainage. The English term, Paddy or Paddi, also originates from the Malayo-Indonesian term, Padi, which means rice plant. In order to avoid confusion between upland paddy fields and man-made irrigated rice growing environment, lowland paddy fields, the authors propose to use the term “sawah” in West Africa. Irrigation and drainage without farmers' sawah farming technologies has proved inefficient or even damaging because of accelerated erosion and waste of water resources. Thus, the development of irrigation has been slow. In the absence of water control, fertilizers cannot be used efficiently. Consequently, the HYVs perform poorly and soil fertility cannot be sustained. Hence, the green revolution cannot take place. This is a Sawah hypothesis for green revolution in West Africa. Like the lacking of TSUNAMI concept, which made the tsunami disaster seriously exaggerate on December 26, 2004, the lacking the concept and appropriate technical term “Sawah” made serious confusion in the research and development of rice cultivation in WA. Contrary to Asian farmers' fields, Sub Sahara African farmers' fields, and therefore farming technologies, are not ready to accept irrigation, fertilizer and high yielding varieties. Although we had been discussed on research and development on irrigation, fertilizers and HYV last thirty years, we never discussed that the prerequisite are lacking in majority of Sub Saharan African farmers' fields. The concept and technologies of Sawah is such an example. Simply speaking, the basic infrastructures for green revolutions are lacking. Apart from natural environmental reasons, the background for this cause can be found in the historical tragedies last five centuries. The soils formed in uplands and the nutrients released during rock weathering and soil formation processes in uplands are accumulated in lowlands (geological fertilization). Watershed agroforestry through the integration of upland forestry, upland farming and lowland Sawah systems in a watershed is a typical model of watershed ecological engineering. The optimum land use pattern and landscape management practices optimize the geological fertilization through the control of optimum hydrology. This is an eco-environmental basis for long-term intensive sustainability of Sawah based rice farming in Asia. Asian monsoon area showed the highest delivery of sediments by soil erosion where have the major distribution of sawah based rice farming. For upland farming, such soil erosion destroys farming productivity, however for lowland sawah based rice farming such eroded sediments become the parent materials of lowland sawah soils. The soil erosion is compensated by new soil formation in sustainable ecosystems of a watershed. The sawah systems can be managed as multi-functional constructed wetlands. Submerged water can control weeds. Under submerged condition, because of reduction of ferric iron to ferrous iron, phosphorous availability is increased and acid pH is neutralized, hence micronutrients availability is also increased. These replenishment mechanisms encourage not only the growth of rice plant but also encourage the growth of various algae and other anaerobic microbes that increase the nitrogen fixation. The quantitative evaluation of nitrogen fixation, 20 – 200 kg/ha/year, in sawah systems including the role of algae will be important future research topics. The above macro- and micro-scale mechanisms explain why the sustainable productivity of 1 ha of lowland sawah is equivalent to more than 10ha of upland fields. The development of 1 ha of sawah opens the field for the afforestation in the degraded uplands. Thus if we can develop sawah systems 20million ha in West Africa in the next 50-100 years, we can expand an afforestation area by 200million ha in West Africa. The forest also conserves soils and water and improves soil fertility, which in turn promotes sustainable rice production of lowland sawah systems.