Riparian zones are an important part of the natural ecosystem relative to the assimilation and transformation of nutrients before they move from the terrestrial landscape to ditches, streams, and lakes. In the USA, riparian buffers have become one of the most widely used conservation practices frequently functioning in concert with whole farm nutrient management plans. They are especially useful for protecting water resources from nonpoint source nitrogen pollutions. This usefulness is generally associated with their substantial denitrification capacities. Studies on the variation in levels of denitrification as well as completeness of denitrification will be discussed for heavily loaded buffers contiguous to animal waste application areas as well as moderately fertilized cropping systems. The influence of landscape position and soil characteristics will also be discussed.