Saturday, 15 July 2006

Meeting the Rice Production and Consumption Demand Of West Africa with Improved Soil and Water (Sawah) and Nutrient Management Technologies.

Kwame Osafredu Asubonteng1, Benjamin Adiyiah1, Tsugiyuki Masunaga2, and Toshiyuki Wakatsuki3. (1) Soil Research Institute, Academy Post Office, P.M.B, -, Kwadaso - Kumasi, Ghana, (2) Faculty of Life and Environmental Science, Shimane Univ, 19-25 Shoohokudai, Matsue, 6908504, Japan, (3) Faculty of Agriculture, Kinki Univ, 2-3-22 Tomio, Nara, 631-8505, Japan

Rice production in Ghana and West African sub-region in general has increased frown 1970 to 2000, but it is still far below the consumption needs. Presently, countries in the West African sub-region imports much of their rice needs. It is estimated that 64% (120 million U.S. Dollars) of the Ghana rice needs of 520,000 metric tonnes is imported. The average rice yield obtained by most small-holder rice farmers in West Africa are still very low (0.5-1.5 t ha-1). Fortunately, inland valley swamps, which have specific hydrological conditions and have been cited as having potential or the development of rice-based small holder farming systems occur abundantly in the West African sub-region. However, there are major constraints like water control, weed infestation and low soil fertility which hinder rice production in them. Therefore, an improved soil and water management system known as sawah technology (bunding, leveling and puddle fields for irrigated rice cultivation) which is characterized by nutrient replenishing mechanisms with intrinsic resistance to erosion was studied alongside the traditional slash-and-burn rain-fed lowland rice farming systems at a bench mark site in an inland valley bottom in Ghana. Different organic and inorganic fertilizers were tested under the different systems. The experiment was a split-plot design with local farmers' field practice and sawah system as the main plots and six fertilizer treatments T1-control; T2-N45P30K30; T3-N90P60K60; T4-4t/ha poultry manure; T5-4t/ha cowdung; T6-4t/ha decomposed rice straw as subplots. Productive tillers, straw and grain yield, nitrogen uptake efficiencies and the chemical dynamics of the soils were monitored. The results revealed that the sawah system resulted in greater number of productive tiller, higher straw production and higher grain yield. Paddy yield obtained under sawah system was over 400% (Ave. 1.3 t/ha). Among the fertilizer treatments, the poultry manure, relatively rich in both Nitrogen (N) and Phosphorus (P), and use of the inorganic fertilizer combination N90P60K60 kg/ha, which is the recommended rate for rice, in Ghana, exerted similar effects on grain yield under both production systems. Agronomic N Uptake Efficiencies (ANUE) Agronomic N Efficiencies (ANE) in both mineral and organic fields were considerably higher under the sawah system. The ANES' of the sawah fields were more than double those of the farmers' yield practice. Even in the control plot under the sawah system, where there was no application of fertilizer, the grain yield obtained was 2.5 t/ha which was equal to the grain yield obtained in the plots with local farmers' field practice, where recommended rate of fertilizer for rice (N90P60K60 Kg/ha) was applied. A possible explanation for the success of the sawah technology is that flooding of paddy soil positively changed its chemistry by increasing soil pH, available phosphorus and nitrogen and reduction of weeds which is favourable to rice growth. The study therefore indicates that the adoption of the sawah technology and/or use of organic residues (poultry manure) by our small-holder rice farmers can help West Africa achieve self sufficiency in rice production.

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