Temporal variation in soil quality and carbon sequestration potential of different cropping systems in Arid and Semi-Arid parts of South Eastern Kenya

The use of incorrect agricultural methods and utilization of land, excessive inorganic chemical applications, misguided cultivation, and nutrient mining have all contributed to a considerable deterioration in soil health globally. To meet the requirements of growing inhabitants, farmers have turned to unsustainable methods including monoculture, excessive use of pesticides and fertilizers, and increased agricultural intensification. A study to determine the seasonal variation of soil quality under different cropping systems and carbon sequestration potential was done during the years 2018 and 2019 in Kauwi and Zombe Wards of South Eastern Kenya. Five cropping systems namely, vegetable, cereal, fruit, and agroforestry were selected, whereas uncultivated land was considered as control. During the typical long (MAM) and short (OND) rainfall seasons, composite soil samples were taken from the cropping systems at random, making the treatment combinations ten. Each farming system had surface soil samples obtained from a depth of 0 to 15 centimetres. Two-way ANOVA was used to analyze the results. The results revealed that the influence of cropping systems on seasonal variation of soil quality parameters varied significantly (p<0.05). Further, the interaction between cropping systems and seasons significantly influenced soil pH and soil organic carbon. The short rain season registered lower soil pH values across all cropping systems. Soil Organic Carbon was found to be highest in vegetable-based cropping systems during short and long rain seasons. Electrical Conductivity was highest during the long rain season across all cropping systems. Soil bulk density was lowest during the short rains and under uncultivated land. NPK varied significantly across the cropping systems in the different rain seasons. Higher carbon stock was found in the Zombe ward as compared to the Kauwi ward. Carbon density values were noticed to be highest under Vegetable-based cropping systems in both study locations. This can be ascribed to the heavy application of organic and artificial fertilizers by farmers to increase yields and profits. Based on the results, Vegetable and agroforestry cropping systems were found to contain the highest amounts of soil carbon, and therefore, with the potential to sequester the highest amount of soil carbon. Both tiers of government should promote vegetable and agroforestry cropping systems to minimize the effects of climate change