Improving the Charge Properties of Highly Weathered Soils of the Kinshasa’s Hinterland by Using Pink Dolostone from Kimpese and Local Coffee Waste.

The Arenosols of Kinshasa’s hinterland are characterized by a low chemical fertility, an acid reaction and a mineralogical composition limited to quartz, kaolinite and some residual oxides of Al and Ti. The effects of pink dolostone from Kimpese (PDK) and coffee waste (CW) application on the charge properties of the Batéké soils were studied in vitro using a completely randomized experimental design. Different amounts of 6.4 g CW. (kg sol)-1 and 1748 mg PDK. (kg sol)-1, corresponding to 20.0 t.ha-1 of CW and 5.46 t.ha-1of finely grounded PDK were mixed with topsoil (0-25 cm), and incubated and leached for 3, 6, 9, and 12 months. The use of CW and PDK as amendments resulted in a significant (p<0.05) increase in chemical soil fertility indicators (pH, available phosphorus, sum of basic cations, organic carbon and total nitrogen content and base saturation. The study revealed that CW is an excellent organic manure and NPK nutriment provider for crops. Studying the charge properties of the Batéké soils, it was found that the application of CW and PDK to soil, (i) significantly increased the soil pH (pH0.002), (ii) decreased the point of zero charge (pH0), (iii) substantially increased the negative charge components, CECT and CECB, with concomitant decrease of the positive charge component (AEC). Furthermore, a strong exponential correlation was found (R2 = 0.94; y = 0.97 e-0.63x) between the negative charge CECT and the difference (pH0 – pHsol), indicating that the Gouy-Chapman model is likely an alternative option for sustainable management of the Kinshasa’s hinterland soils. The PDK and the CW materials have thus, all requirements to improve significantly the charge properties of the highly weathered Batéké soils. Télécharger l'article