Effect of a Sawah-Based Farming System on Rice Cultivation in the Inland Valley Bottom of the Ashanti Region, Ghana.

Abstract

The contribution of the sawah system (bunding, leveling, and puddled fields to irrigated 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, P205 60, and K2O 60 kg ha-I 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. Key words: agronomic efficiency / Ghana & West Africa / inland valley bottom / inorganic fertilizers 1 rain-fed lowland condition / organic manures / phosphorous deficiency / sawah system The agricultural productivity index in Ghana and other countries in West Africa fluctuates mainly because the country's agriculture is rain-fed and subsistence farmers relying on the rain are the main backbone of farming in the country. The majority of farmers still practice the traditional shifting cultivation method of farming. Under this system, farmers clear the native vegetation by the slash-and-bum method and then grow crops. The efficiency of shifting cultivation depends mostly on the duration of the fallow period and the nature and density of the fallow vegetation. Rapid increases in human population and the associated increases in demand for farmland and wood products have overburdened this traditional cultivation method. Long fallow periods, which in the past lasted 10 to 25 years, have been shortened drastically (to one or two years) or disappeared in areas like the valley bottom sites in Ashanti where rice is cultivated yearly. This has resulted in increasing degradation of farmland increasing infestation of problem weeds, and declining yields and production of food crops