Abstract:
Releasing pattern of nitrogen and other nutrients from plant residues is a matter of
highly concerned as it is important in managing nutrients to maximize the crop
productivity of a given soil. Therefore, this study was carried out to examine the
releasing pattern of inorganic nitrogen (NH/-N and N 0 3' -N) in a saline soil
amended with plant residues of three different species. A factorial combination of
two soil types (normal and saline soil) enriched with three types of plant leaves
(Sesbania, Caliandra and Gliricidia) and soil sample without any leaf material with
four replicate were used in the laboratory incubation. Nitrogen mineralization of soil
was determined up to 70 days after treating with plant leaves. Data were statistically
analyzed using SAS package. The amount of N H /-N released was varied
depending on the plant species and no treatment was found to be significant.
Sesbania leaves treated soil showed the highest and rapid release of nitrogen,
followed by Gliricidia and Caliandra. The ammonification process reached to the
maximum at 7, 21 and 28 of incubation respectively in Caliandra, Gliricidia and
Sesbania treated soils. Thereafter the nitrification process dominant and N H /-N
was found converting to N 0 3' -N. However, saline soil showed significantly low
N H /-N and N 0 3' -N contents compared to normal soil. Meanwhile nitrogen
mineralization indicated that leaves of Caliandra which has low nitrogen content
(3.85 %) was unable to provide available nitrogen in short term. Soil pH and EC of
all treatments were highly varied throughout the incubation period. The salinity
caused reductions in nitrogen mineralization and total mineralized nitrogen in the
soil. The quality of nitrogen constituents in plant materials seemed to play a vital
role in the nitrogen mineralization in the saline environment.
