A Comparative Assessment of Soil Fertility on Flood Recession (Molapo) and Dryland Farms: The Case of Xhobe Settlement in the Okavango Delta World Heritage Site

Abstract

Soil fertility assessment is a crucial step in determining the productivity of farms in a specifi c locality. In this paper total nitrogen, phosphorus, soil organic matter and pH are compared in two arable farming systems namely flood recession and dryland farms. The objective of the research is to assess nutrient dynamics in soils of the two farming systems. Farms were randomly selected and stratifi ed sampling technique was used to collect soil samples on flood recession and dryland farms. The collected soils were analysed for the afore mentioned parameters. The results indicate that nutrient pools increase with upturn in moisture and more alkaline soil conditions. Nitrogen and soil organic matter contents are higher in soils from the fl ood recession farms while phosphorus was not detected at all. Soils in the flood recession farms are more basic over dryland ones with the former having an average pH of more than 7 and the latter less than 7. A pH value below 7 indicates the soil is acidic, while values above 7 are alkaline or basic. There is higher organic matter accumulation in fl ood recession farms, which is associated with high decomposition rate that lead to the release of nitrogen into the soil. Therefore, with respect to soil organic matter and nitrogen contents, fl ood recession farms are more fertile than dryland farms, whereas with regard to phosphorus there is a limited supply in both farming practices. In conclusion, an external input of phosphorus or organic fertilizer is needed to improve the productivity of farms in Xhobe settlement and the rest of farms located in the Okavango Delta Ramsar site so that farmers can have increased yield and meet their household food security needs.