COMPARATIVE ANALYSIS OF SOIL ORGANIC CARBON IN THE SOILS OF DOWA DISTRICT

Abstract

A comparative study on soil organic carbon (SOC) and power of hydrogen (pH) levels was conducted in soils of Dowa district in 2017 with an aim of determining their changes over a period of three decades. Soil samples were collected from pits by excavation into plastic bags while observing and documenting land nuse activities from 27 previously sampled points under the baseline study conducted in 1987 by MoAFS. The soil samples were analyzed for SOC and pH values at the University of Malawi – Chancellor College Research and Chemistry Laboratories using Walkley-Black Wet Combustion method for SOC and pH meter for soil pH. The 2017 and 1987 data were compared using paired sample t-test. The results indicated significant changes between the baseline SOC status and the 2017 SOC levels (P <0.001; α = 0.05) and pH (P <0.02; α = 0.05). SOC and pH have decreased by 37% and 6% respectively. The study also revealed that frequencies of land use activities such as agriculture and settlements, have increased while woodlands/forests and grasslands have decreased. Spatial distribution revealed a decreasing trend of the SOC and pH from west, central to north western parts of Dowa for 2017 datasets but higher in the eastern and southern parts of the district. Factors such as changes in land use coupled with differences in soil type have attributed to the observed pattern. Basing on the findings, it is recommended that land use practices associated with decrease in SOC and pH such as agriculture and settlements should integrate soil carbon improvement strategies to ameliorate soil nutrient status in the district to meet the growing demands for food and environmental sustainability goals.