INJURY OF LEATHERLEAF FERN AND TOMATO FROM VOLATILIZED AMMONIA AFTER FERTILIZER APPLICATION

A commercially blended 7-2-11 fertilizer containing 27 g . kg(-1) solu ble ammoniacal nitrogen (NH4-N) was evaluated for ammonia (NH3) volati lization and injury to leatherleaf fern (Rumohra adiantiformis) and an indicator plant, tomato (Lycopersicon esculentum). Closed system labo ratory incubation studies on pH-buffered sand medium indicated a very highly significant response (p less than or equal to 0.001) of NH3 vol atilization to sand pH. The greatest risk from NH3 emissions at pH 8.6 and 32 degrees C appeared to be in the 5 to 70 hour period after fert ilizer application. Gypsum (CaSO4) did not affect NH3 volatilization. Ammonium nitrate (NH4NO3) was identified as the main source of NH3 vol atilization from this fertilizer formulation, while on an equal mass b asis, ammonium sulphate [(NH4)(2)SO4] was more important. Both tomato and immature leatherleaf fern fronds were highly sensitive to volatili zed NH3 from the fertilizer. A critical phytotoxic NH3(aq) concentrati on in sand solution of 0.14 mM was estimated for immature fern fronds. Mature fern fronds were significantly more tolerant of NH3 emissions, which may explain their observed resistance to NH3 injury in the fiel d. Assessment of selected soil and irrigation water pH's from a leathe rleaf fern growing area in Florida indicated a strong likelihood that volatilized NH3 injury to foliage can occur under field conditions.