Assessment of aggregate stability and soil organic carbon sequestration in Alfisols of Guinea Savanna

Abstract

Soil aggregate stability is a vital indicator for improving soil quality and controlling soil losses. This study aimed to assess the effect of fallow forage legumes and fertilizer application on wet and dry stability aggregate and soil organic carbon on Alfisols of Guinea Savanna, Nigeria. The study was conducted at the Institute for Agricultural Research (IAR) experimental field, Samaru Zaria. Treatment consisted of 3 plots (Centrosema pascuorum (Cp planted), Macrotyloma uniflorum (Mu planted) and control-natural vegetation regrowth). The soil samples collected were dried at room temperature and then separated into six aggregate fractions. Aggregate stability assessment results showed that dry stable aggregate fraction was significantly influenced by fallow management practice where Cp planted fallow recorded the highest amount in soil aggregate sizes of 2000 μm (0.99 g kg-1). Concerning wet stable aggregate, the proportion of 2000 μm sized aggregate fraction had the highest value (0.22 g kg-1) under treatment Cp. However, 0 kg N ha- 1 -1 produced the highest quantity in 2000 μm (0.23 g kg ) sized stable aggregates, and there was no significant difference in Nitrogen and Phosphorus application rates. The wet mean weight diameter (MWD) was significantly affected by forage legume with Mu planted fallow having the highest value (0.40 g kg-1) while the dry MWD aggregates with Cp recorded the best value (1.37 g kg-1). Cp planted fallow sequestered more carbon (0.65 g kg-1) in the 500 µm aggregates fraction. NVR contributed the highest carbon (0.80 g kg-1) under 50 µm sized aggregates. For carbon content in <50 µm sized aggregates, Mu produced the highest carbon (0.72 g kg-1) in the fraction. Conclusively, the type of management practices affects the soil aggregation size fractions, which increased soil organic carbon sequestered.