SOIL, PLANT AND ATMOSPHERIC CONDITIONS AS THEY RELATE TO AMMONIA VOLATILIZATION

Gaseous ammonia (NH3) transport is an important pathway in the terrest rial N cycle. In the atmosphere NH3 neutralizes airborne acids and is a major factor determining air quality and acid rain deposition patter ns. Redeposition of atmospheric NH3 plays an important role in the N b alance of natural ecosystems and has been implicated in forest decline , plant species change and eutrophication of surface water. Much of th e N in soil-plant animal systems can be lost to the atmosphere, partic ularly with surface applied livestock waste, or urea and anhydrous amm onia fertilizers. Plants can have a significant impact on NH3 transpor t because they can both absorb and desorb atmospheric NH3. Under condi tions of low soil N or high atmospheric NH3 concentrations, plants abs orb NH3. Under conditions of high soil N or low atmospheric NH3 concen trations, plants volatilize NH3. This article discusses methods for ev aluating NH3 transport in the filed, the rate of NH3 volatilized from fertilizer application, and the effects of plants on net NH3 transport .