AMMONIA EXCHANGE FROM CORN FOLIAGE DURING REPRODUCTIVE GROWTH

Developing solutions to atmospheric environmental problems requires a better understanding of chemical processes occurring in each component of the ecosystem. Volatile NH3 loss from plant foliage complicates th e assessment of NH3 emissions from agricultural activities, The object ive of this study was to use N-15 methodology to identify time of occu rrence, magnitude, and direction of NH3 exchange between corn (Zea may s L.) fertilized with enriched N-15 and the atmosphere during reproduc tive growth, Ammonia was collected by drawing air over leaves, ear sho ots, and whole plants and trapping the NH3 on oxalic acid-impregnated filter disks, Filter disks were analyzed by ANCA-MS procedures for tot al N and atom % N-15, A, exchange of NH3 between corn plants and the a tmosphere was found to occur during all sampling periods, This suggest s that the release and capture of free NH3 is an active component of t he metabolic processes taking place in corn plants during reproductive growth, For corn under nonlimiting N fertility, the direction, rate, and magnitude of NH3 exchange from leaves does not appear to be a func tion of ambient atmospheric NH3 concentrations. Determining the true l oss or gain in N between corn plants and the atmosphere during reprodu ctive growth is very difficult as a result of this continuous exchange of NH3, The amount of net N lost from a corn crop will be less than t he amount indicated by measurements of isotopic loss, because both int erchange between plants and deposition on soil and plants may take pla ce within the field.