Improving the quality of sandy soils of the Batéké plateau (D.R. Congo) by using local geological materials and industrial organic waste products

Abstract

In tropical Africa, a productive and sustainable agricultural system is one of the fundamental priorities to the well-being and food safety of the population, and it constitutes a cornerstone of development. The fast growing African population and the continued soil fertility degradation require special management practices for sustaining agricultural productivity over a long period of time. This is of particular importance to the province of Kinshasa (DR Congo), where the sandy soils covering the major part ofits hinterlands are very marginal and severely constraining the food supply to the capital. Furthermore, the farmers and local population have only limited capital at their disposal and therefore cannot afford regular applications of conventional chemically processed fertilizers. The use oflocal geological resources (agrominerals, rock fertilizers or petrofertilizers) and organic industrial wastes in the crop production systems can be an alternative solution to enhance soil productivity.This study has been conducted within the frame of research for appropriate methods of sustainable management of the sandy soils of Kinshasa's hinterland, in order to ensure and guarantee the food security. It consists of scientific research of the use of greens tone of Gangila, pink dolomite of Kimpese, rock phosphate of Kanzi and coffee waste to improve the quality of the sandy soils on the Bateke plateau, being the eastern part of Kinshasa's hinterland. The study comprises 7 different chapters. The first two chapters are devoted to the physical environment of the Bateke plateau and to a literature review on the use of agrominerals and industrial coffee wastes in agriculture, as well as to the theoretical concepts used to describe surface charges of highly weathered, tropical soils. The 5 last chapters deal, respectively, with the agropedological status of the soils, the impact assessment of Acacia auricullformis forest on the chemical fertility of soils, the characterization of the amendments, the reactions of these amendments with the soils, and their effects on plant growth and mineral nutrition.The determination of the agropedological status of the soils showed that the Bateke sandy soils, classified as Rubie Ferralic Arenosols (Dystric) in WRB (FAO, 2006), and as Isohyperthermic Ustoxique Quartzipsamments according to USDA Soil Taxonomy (Soil Survey Staff, 2006), have a clayey mineralogy limited to kaolinite and residual oxides of Al and Ti. These soils are dominated by variable charge colloids; they present an acid reaction with Al and Mn toxicities, and have low organic matter and mineral nutrient contents.