It is often suggested but so far not substantiated that soils with a higher fungal/bacterial (F/B) ratio retain nitrogen better. If this were true, it would be wise for farmers who want to reduce the environmental impact to increase this F/B ratio. We did field studies on experimental plots and on commercial farms and found that lower fertilizer rates led to higher fungal biomass in grassland soils. In incubation studies with intact soil columns we showed that soil with a higher fungal biomass had lower leaching and denitrification rates because of lower mineralization and nitrification rates while maintaining production levels.