Mr Md Noor E Alam Siddique1, A/Prof Lisa Lobry de Bruyn1, A/Prof Chris N. Guppy1, Dr Yui Osanai1
1School of Environmental and Rural Science, University of New England, Armidale, Australia
The assessment of temporal and spatial variation in soil organic matter (SOM) and soil reaction trend can identify the potential threats to soil fertility and long-term sustainability of farming system. This study quantified the spatiotemporal variations in SOM and soil pH of paddy soils between 1990 and 2010 in the northern Bangladesh. Soil legacy data sets collected from these two time periods were categorised according to prevailing soil series, physiographic position and major soil types. SOM status in all soil types was generally low (10-17 g/kg). SOM content has increased marginally, but remains low, which is hypothesised to be related to increasing cropping intensity and fertilisation over this same period. Inundation land type and local differences in smallholder management is hypothesised to have influenced SOM variability, however land management has yet to be investigated. Soil reaction trend between 1990 and 2010 measurements in agricultural soils has decreased by 0.5 units with a 50% increase in soils falling below a pH of 5.5 over the 20 year survey period. Soil acidification is potentially a combination of inefficient and excess use of ammonium based fertilisers with highly variable application rate, low input from crop residues, and underlying light texture topsoils and high rainfall. We speculate that whilst acidification may continue to fall with more intensive land use, SOM has reached a stable, but very low, equilibrium and is unlikely to fall further. Therefore, future research priorities addressing C and N dynamics, optimising the use of fertilisers (particularly N), better crop residue management and lime based amelioration of acidic soils will improve the sustainability of rice-based farming system in the northern Bangladesh.
Md Noor E Alam Siddique is a Senior Scientific Officer from the Soil Resource Development Institute, Ministry of Agriculture, Bangladesh. He is currently in second year of PhD at University of New England, Australia. He has background on Agronomy and Soil Science. He works on soil fertility management, soil characterization and soil survey.