In this study the fate of nitrogen from liquid dairy cattle manure and from composted cattle manure was investigated in two field experiments. These were conducted at the Elora Research Station of the Ontario Ministry of Agriculture, Food and Rural Affairs in collaboration with Drs. D.L Burton, E.G. Beauchamp and R.G Kachanoski, and at Winchester Research Station of Kemptville College of Agricultural Technology in collaboration with W.E. Curnoe. The objectives of the experimental programme were to investigate the fate of nitrogen from the mineraland organic-N in cattle manure applied in spring or fall, to evaluate the use of cover crops and straw residues for conserving N from fall-applied manures or fall-ploughed alfalfa hay.