Rwanda small marais development study : investigations into the agronomy of two small marais -- Nyarutovu and Ilibunga

Small marais, as opposed to their larger counterparts in the flood plains, are found scattered throughout the country with a high concentration in the Central or High Plateau region of Rwanda. The marais have long been considered a last resort for expanding cultivated acreage in landlocked Rwanda, which is facing problems of overpopulation and land shortage and fragmentation. Most marais are now cropped, and access to plots is controlled at the communal level, since land is under state ownership. Few development schemes in the past have been concerned with soil characterization and existing cropping systems in small marais. Most have dealt with hydrologic aspects such as drainage and irrigation, although with relative success. There is thus a need to gain some insight into the nature and importance of soil constraints in smail marais and their effects on the efficiency of existing cropping systems. This paper reports on research conducted in Rwanda from July 3 through November 15, 1987, in order to characterize the fertility of the soils of two small marais and to relate fertility and soil water parameters to the performance of the traditional cropping system, sweet potatoes (Ipoomoea batatas) on raised beds. Secondary objectives were to evaluate fertilizer response and assess growth of alternative crops on marais soils. The main body of the report comprises three sections: the first contains background information on the two marais studied, the second describes in detail the crop-soil-water system study and the third outlines the fertilizer trials. (Author abstract)