As population pressure on land grows rapidly in Kenya, rural farmers have started to intensify land use, which has led to the emergence of a new maize farming system. The new system is characterized by the adoption of high-yielding maize varieties, the application of chemical fertilizer and manure produced by stall-fed improved dairy cows, and intercropping, especially the combination of maize and legumes. This study aims to explore the determinants of the new maize farming system and its impact on land productivity and household income. We examine not only the impacts of new technologies and production practices but also the impact of the entire new maize farming system by generating an agricultural intensification index based on a principal component analysis. The estimation results show that an increase in sub-location level population density and a decrease in the land-labor ratio of an individual household accelerate farming intensification, and that the adoption of each new technology and production practice has positive and significant impacts on land productivity. These findings are further supported by the significantly positive impacts of the agriculture intensification index on land productivity.