The effect of organic matter composition on kinetic of gross nitrogen mineralization of peat soils.
H. Purwanto Benito, Watanabe Akira*, Abe Tomonori*, Kakuda Ken-ichi1 Ando
Ho
(*：名大農学部)
There has been a vast increase of land conversion in peat soils for agricultural
use. Investigation of N mineralization rate on peat soils is important
for increasing crop production. Land conversion
may affect the quantity and quality of soil organic matter with subsequent
effect on N ineralization of peat soils. However, soil organic matter composition
that
influences the kinetic parameters of N mineralization has not been fully
understood. Applications of I3C NMR and XPS techniques in analysis of organic
C and N compositions
of peat soils were expected to explain the variation in the kinetic parameters
of N mineralization.
Objective: To investigate the effect of soil organic matter composition under different land use on the kinetic parameters of gross N mineralization of peat soils. Materials and Methods: l ).Peat soils were collected from cultivated and non cultivated areas in Indonesia, Malaysia and Japan. 2). An incubation experiment was conducted under 20??C, 25??C and 30??C for 1,2,4,6,8 and 12 weeks with an addition of 100 mg kg'1 of99.6 atom % of (l5 NFU) 2SO4. The kinetic of N mineralization was expressed by first-order equation. 3). Soil organic C and N compositions were analyzed by ' 3 C NMR and XPS techniques, respectively.
Results: 1. The kinetics parameter of gross N mineralization showed higher
Ea and lower k in the non-cultivated soils than those of the cultivated
soils. 2.
Gross rate of N mineralization negatively correlated with the alkyl
C / O-alkyl C ratio of soil organic matter, whereas Ea value positively
correlated
with
that ratio. 3. None of the concentrations of primary amine N, peptide
N, and aromatic
N that were estimated by XPS showed significant correlation with the
rate of N mineralization. These results indicated that the alkyl C
/
O-alkyl
C ratio
could be used to estimate kinetic parameters of gross N mineralization
in peat soils, which is probably related to the degree of decomposition
of carbohydrates.