Effect of Drying Methods on Losses of Carbon, Nitrogen and Dry Matter from Alfalfa¹

Methods of drying forage samples were examined for their influence on the total C, N, and dry matter (DM) content of ‘Ranger’ alfalfa ( Medicago sativa L.). Forage samples were freeze‐dried; air‐dried in perforated paper bags and on trays; dried in perforated paper bags in mechanical convection ovens at 60, 80, and 100 C; and oven‐dried at 100 C for 90 minutes followed by drying at 60 C, or by air‐drying. All treatments were terminated after 48 hours. Losses in C and N were measured by changes in C:K and N:K ratios. The DM losses were measured by changes in K concentration. Carbon and DM were lost more readily than N by either respiratory or thermochemical processes. These losses resulted in an apparent concentration of N in all forage dried between ambient and 100 C. All treatments, when compared to freeze‐drying, resulted in losses of C and DM. The greatest loss of DM, 5.4% occurred in samples dried at 100 C. Oven‐drying at 100 C for 90 minutes followed by air‐drying caused IDM losses of only 0.2%. Significant differences in actual N content between the various drying methods were not generally observed.