Km. Glasener et Ca. Palm, AMMONIA VOLATILIZATION FROM TROPICAL LEGUME MULCHES AND GREEN MANURESON UNLIMED AND LIMED SOILS, Plant and soil, 177(1), 1995, pp. 33-41
In the humid tropics, legumes are harvested and surface applied as mul
ch or incorporated as green manure. Studies of N dynamics and budgets
from these systems report unaccounted losses of N. Ammonia volatilizat
ion may account for a significant percentage of these unexplained N de
ficits. The main objectives of this study were to: 1) determine the ra
te and amount of ammonia volatilization from organic amendments, both
incorporated (green manure) and unincorporated (mulch), 2) compare amm
onia volatilization of organic amendments on both acid (unlimed) and l
imed soils, and 3) correlate quality, i.e. polyphenolic and lignin con
centration and carbon-to-nitrogen ratio, of the organic amendments wit
h ammonia volatilization and net N mineralization. In an incubation ex
periment, ammonia volatilization losses and net N mineralization were
measured from fresh leaflets of 10 legumes over a three-week period. A
mmonia volatilization losses for the 10 species ranged from 3.4 to 11.
8% of the total N applied in the organic amendment. Lignin content was
negatively correlated to ammonia volatilization. Ammonia volatilized
from mulches but not green manures, on both unlimed and limed soils, s
uggesting that ammonia volatilization is a surface phenomenon and not
affected by soil pH. Net N mineralization was affected by species and
soil pH, but was unaffected by placement (green manure or mulch). For
the farmer in low-input agriculture where N tends to be limiting, vola
tilization losses of N from legume mulch systems could be on the same
order of magnitude as crop removal.