Pl. Mafongoya et al., MINERALIZATION OF NITROGEN FROM DECOMPOSING LEAVES OF MULTIPURPOSE TREES AS AFFECTED BY THEIR CHEMICAL-COMPOSITION, Biology and fertility of soils, 27(2), 1998, pp. 143-148
Nitrogen release patterns from seven leguminous trees were determined
from 8-week laboratory incubations. The quantities of extractable NH4-N and NO3- released to the soil to which the leaves had been applied
was determined at weekly intervals and was related to the initial N, p
olyphenol, and lignin concentration of the leaves. Cumulative N minera
lized was not correlated to initial N, soluble polyphenol and insolubl
e tannin concentrations, but was correlated to lignin and neutral dete
rgent fibre N (NDF-N) concentrations. The ratios of NDF-N:N (r=0.68 at
P<0.05), soluble polyphenol:N (r=0.70 at P<0.05) and (lignin+polyphen
ol):N (r=0.75 at P<0.05) were negatively corre lated with N release. T
otal polyphenol content was not a useful predictor of N release, but t
he reactivity of the polyphenols as measured by their protein-binding
capacity can be a useful predictor. In addition to measur ing the conc
entration of polyphenols, their reactivity with proteins must be measu
red, in order to assess their role in regulating N release. The (ligni
n+polyphenol):N ratio could be used to screen leguminous tree leaves f
or their potential to release N in short-term experiments. This would
allow for rapid screening of a large number of trees without detailed
and expensive field experimentation.