Abstract:
The conversion of soil nitrogen (N) from organic to inorganic forms has been the
subject of several investigations. N mineralization in salt-affected soils is a subject of
much controversy because there are reports of salt induced non-biological
ammonification. This study was therefore carried out to observe trends in N
mineralization in saline soils amended with animal manure.
A factorial combination o f two soil types (normal soil and saline soil) with four
treatments (control, poultry manure, goat manure and cow dung) used in laboratory
incubation. Nitrogen mineralization was determined at 3, 7, 14, 21, 28, 35, 42, 49, 56
and 70 days after the treatments. The experiment was replicated four times and data
were statistically analyzed using SAS package.
The N H / -N content of both soils reached a peak at day 14 followed by gradual
reductions in all treatments. Though, the initial nutrient content of applied manures was
different, no significant differences were found among the treatments in terms of N
mineralization. However, saline soil showed significantly low NH4+ -N content
compared to the normal soil. It was very clear throughout the incubation that no distinct
pattern of treatment behavior could be observed for N 0 3' -N. However, normal soil
maintained a higher N 0 3' -N level throughout the incubation. Therefore, depression of
ammonification and nitrification and the overall decrease in net N mineralization with
increasing pH or salinity were all evidence of the biological nature of N mineralization
in salt-affected soils.