Abstract
The contribution of the sawah system (bunding, leveling, and puddled fields to irrigate rice cultivation) was studied alongside the traditional slash-and-burn, rain-fed lowland rice farming system in the inland valley bottom of the Ashanti region, a semi-deciduous forest zone in Ghana. Different organic and inorganic fertilizers were tested under the different systems. The results revealed that the sawah system resulted in a greater number of productive tillers, higher straw production, and higher grain yield compared to the farmers’ rain-fed lowland practice.
Among the fertilizer treatments, the poultry manure, relatively rich in both N (nitrogen) and P (phosphorous), and the use of the inorganic fertilizers N 90, P2O5 60, and K2O 60 kg ha-1 at the recommended rate for rice exerted similar effects on grain yield under both systems This means the soils were relatively deficient in available N and P. The sawah system had a remarkable effect on N uptake by rice grain and straw in the inland valley bottom. Agronomic uptake N efficiencies and agronomic N efficiencies of fertilized N in both mineral and organic forms were considerably higher under the sawah system in the valley bottom. The present rain-fed lowland condition of local farms in the inland valley bottoms of the Ashanti region of Ghana showed very poor efficiency in the use of fertilized N in both the mineral and organic forms. Our study results indicate that use of the sawah system is a prerequisite for the efficient use of fertilizer to increase rice yield in the inland valley bottom.
