Soil Microbial Biomass Carbon, Nitrogen and Sulphur as Affected By Different Land Uses in Seronga, Okavango Delta, Botswana.
Loading...
Date
2013-10
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Aim: The Okavango Delta at Seronga is fragmented into different land uses ranging from
grasslands to woodland (Ximenia and mopane), often punctuated with cropped and fallow
fields. The influence of land uses on surface (A1 horizon) soil physico-characteristics,
nitrogen, sulphur, carbon, microbial population and biomass were studied to understand
soil variability in order to devise conservation strategies for the area.
Methodology: Total soil nitrogen (N) was analysed using a Leco N analyser, total carbon
and sulphur by CS800 Carbon–Sulphur analyser. NH4
+-N, NO3
- and NO2
- were extracted
with KCl and determined using the indophenol blue method and by Griess-Ilosvay
colorimetric method respectively. Microbial populations were determined by plate count
method. Biomass carbon and flush of nitrogen were determined by fumigation and reinoculation
technique.
Results: All the soils had a high sand content (> 85%). Total soil N was generally very
low, 0.017% in grasslands closest to the channel, 0.013% in cropped fields, 0.007% in
fallow and lowest in woodlands (0.002%). Grasslands showed higher NH4
+-N indicating
low nitrification potential. Even if mopane woodlands had low total N, they had higher
NH4
+-N (0.067 ppm) and low NO2
- compared to other land uses, this could be attributed to
their inherent nitrification inhibition ability. No NO3
--N was detected in these soils,
probably due to the low nitrification ability and high leaching capacity of sandy soils. Microbial biomass C and population were highest in the grasslands and cultivated soils,
while the woodlands had lower levels.
Conclusion: Seronga soils have very low N, with the least in the woodlands furthest from
floodplains. Grasslands closest to the channel basin had significantly higher total N, C
and microbial biomass C but low S as opposed to the woodlands further from the
channel. Cultivated areas had increased N and C levels and microbial biomass C
compared to the woodland probably due to incorporation of crop residues and animal
manure. The paucity of nitrifiers and undetectable NO3
--N indicate a low nitrification
potential and a high leaching ability of the soils. Fallowing of fields resulted in a decline in
nutrient status.
Description
Keywords
Mopane soils, Ximenia woodlands, grassland, soil nitrogen, microbial biomass
Citation
Mubyana-John T, Masamba W R L. Soil Microbial Biomass Carbon, Nitrogen and Sulphur as Affected By Different Land Uses in Seronga, Okavango Delta, Botswana. British Journal of Environment and Climate Change. 2013 Oct-Dec; 3(4): 628-639.