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Ammonia Exchange at the Land Surface 1
Author(s) -
Lemon Edgar,
Van Houtte Raymond
Publication year - 1980
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1980.00021962007200060005x
Subject(s) - biosphere , sink (geography) , atmospheric sciences , ammonia , atmosphere (unit) , environmental science , nitrogen , vegetation (pathology) , chemistry , absorption (acoustics) , trifolium repens , agronomy , nitrate , environmental chemistry , ecology , meteorology , biology , geology , materials science , physics , geography , medicine , cartography , organic chemistry , pathology , composite material
Studies of NH 3 exchange between plant leaves and air have mostly been made in controlled chambers where the concentrations were far above the ambient atmospheric levels usually found in nature. Under such conditions leaves act as an infinite sink for NH 3 . More recent controlled chamber studies, however, have shown NH 3 evolving from leaves when concentrations were nearer to those of the atmosphere. In this study we measured both NH 3 absorption and evolution by vegetation under field conditions using micrometeorological techniques where vertical profiles of wind and NH 3 are measured. Both evolution and absorption strongly suggest that plants have a compensation point for NH 3 . Data are presented for fields of quackgrass ( Agropyron repens L.), soybeans ( Glycine max L. Merr.) and alfalfa ( Medicago sativa L.). Computer simulation confirmed that vegetation exchange is concentration dependent. We speculate that plants (and soil) keep atmospheric NH 3 in check, at low concentrations, with winds moving it from N rich to N poor ecosystems. Dispersed sources of NH 3 from crop lands are probably increasing due to more fixed N in farming. Thus the added NH 3 due to man's activity probably increases the net global biosphere uptake of both N and C.