Nitrogen (N) is an important nutrient for plant growth, and the N cycle mediated by microorganisms supplies inorganic-N to plants. The N cycle is one of many microbial functions in soils but serious soil degradation, reported in sub-Saharan Africa, can potentially impact the functions. In this study, I focused on one of the functions, nitrification process, which supplies NO3⁻ but leads to N loss from soils. The purpose of the study was to investigate how changes in land-uses, the main cause of soil degradation, affect the nitrification functions and the microbial community of nitrifiers. The shaken-slurry method was used to investigate the nitrification functions and microbial properties in two land-uses (Natural land, Farmland) at three sites in Zambia. As a result, the farmland showed higher nitrification potential and lower organic-N retention than the natural land. Moreover, the microbial community of ammonia-oxidizing bacteria (AOB) was more susceptible to the land-use change than that of ammonia-oxidizing archaea (AOA). Nitrogen fertilization on farmland can especially transform the AOB community into a nitrification-specific form which has accelerated nitrification and low organic-N nutrient retention. This suggests that microbes responding to the land-use changes and the consequent acceleration in the nitrification might contribute to soil degradation.