He is interested in atmospheric deposition, acid rain, soil acidification and liming, nutrient (especially nitrogen) cycling in the biosphere, and sustainable agriculture. His recent research on nitrogen cycling has focused on nitrogen deposition from the atmosphere and included around 15 years of fruitful collaboration with colleagues at the China Agricultural University, quantifying and providing solutions for China's serious air pollution. Keith joined Rothamsted Research in 1974 with skills in chemistry and mathematics, specifically soil chemistry and surface chemistry, including potassium and phosphorus availability in soils. During his career, he acquired skills in nitrogen cycling, especially losses through leaching and denitrification, and microbiological mediation of those processes, carbon cycling and climate change. Keith is currently a member of the Newton-funded UK-China Virtual Joint Centre for Improved Nitrogen Agronomy (CINAg) and the Long-Term Experiments National Capability team. He also spends a significant amount of time engaging in knowledge exchange with farmers. He recently wrote and taught a soil biology course for NIAB's ARTIS training programme, and he is a council member of the International Fertiliser Society and a member of the policy and strategic development committee of Linking Environment And Farming (LEAF).