Soil and Irrigation Water Quality Evaluation : Case of Katumba Irrigation Scheme in Malawi

Crop production under irrigated agriculture faces numerous challenges including premature drying and poor yield due to poor soil and water quality. Crops such as maize and beans have been failing to yield optimally while leafy vegetables have been experiencing premature drying up at Katumba Irrigation Scheme in Malawi. A study was conducted to identify possible causes and solutions to the crop production challenges. In-situ and laboratory measurement of soil and water chemical and physical properties were employed to quantify salt concentrations of the soils and irrigation water to ascertain if the crop production problems were attributable to mineral salt deficiencies or excesses. The study has shown that irrigation water salinity levels were above recommended ones while soil calcium, magnesium and potassium contents and cation exchange capacity were low. The soils had high exchangeable sodium percentages implying presence of sodium hazard. Mineral supplement and organic matter applications through compost or farmyard manure has been recommended to help supplement the deficient nutrients and improve drainage and cation exchange capacity of the soil. Provision of subsurface drainage through construction of open ditches has also been recommended to enhance drainage thereby increasing leaching of salts and minimizing build-up of salinity and exchangeable sodium. The study has also recommended the need to explore growing salt tolerant crops and changing the irrigation method to drip irrigation