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Nitrogen mineralization in subtropical paddy soils in relation to soil properties, organic matter fractions, and fertilizer management

MD Abdul Kader UGent (2012)
abstract
The N requirement for paddy rice cultivated in Bangladesh amounts to approximately 80 kg N ha-1. Lack of knowledge on N mineralization from soil organic matter (SOM) leads farmers to fill up this N requirement exclusively by costly mineral fertilizers, which have typically an efficiency of less than 40%. After decades of searching for a practical tool to estimate the N mineralization capacity of soil, there is still no consistent methodology. This PhD aimed to assess routinely analyzed soil parameters, different physical and chemical fractions of soil organic matter (SOM) and lastly enzyme activities as predictors for the net N mineralization in Bangladeshi paddy soils. Soils were collected from 25 farmers’ fields and two long term field experiments on contrasting soil types, namely on a highly weathered ‘terrace soil’ and on a younger ‘floodplain soil’. Fertilizer management had a significant but contrasting impact on soil N mineralization within both long-term experiments. Bio-availability of N increased in the terrace soil experiment with increasing soil N content, logically in relation to application of fertilizers and organic amendments. On the contrary there was a relatively stronger stabilization of soil N against anaerobic mineralization with higher paddy soil N and C contents in the floodplain experiment and in the set of farmers’ fields. We further investigated SOM quality through physicochemical fractionation of the SOM. In the terrace soils experiment some of the physicochemical SOM fractions were found useful predictors for both aerobic and anaerobic N mineralization. However, none qualified as predictor of anaerobic N mineralization for the floodplain experiment and the set of farmers’ fields. An novel fractionation procedure with sub-critical water extraction yielded a similar limited outcome as for none of the isolated subcritical water extracts the N contents correlated with the anaerobic N mineralization rate. Finally we measured three enzyme activities relevant to N cycling in soil and all were found to be significantly influenced by management. Over all investigated soil parameters in this PhD research L-glutaminase activity was found to be the most useful predictor for the anaerobic N mineralization rate.
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author
promoter
UGent and UGent
organization
alternative title
Stikstofmineralisatie in subtropische paddy bodems in relatie tot bodemeigenschappen, organische stoffracties en bemestingsbeheer
year
type
dissertation (monograph)
subject
pages
IX, 213 pages
publisher
Ghent University. Faculty of Bioscience Engineering
place of publication
Ghent, Belgium
defense location
Gent : Faculteit Bio-ingenieurswetenschappen (A0.030)
defense date
2012-04-13 16:00
ISBN
9789059895133
language
English
UGent publication?
yes
classification
D1
additional info
dissertation consists of copyrighted material
copyright statement
I have transferred the copyright for this publication to the publisher
id
2083199
handle
http://hdl.handle.net/1854/LU-2083199
date created
2012-04-10 17:15:13
date last changed
2012-04-11 08:52:39
@phdthesis{2083199,
  abstract     = {The N requirement for paddy rice cultivated in Bangladesh amounts to approximately 80 kg N ha-1. Lack of knowledge on N mineralization from soil organic matter (SOM) leads farmers to fill up this N requirement exclusively by costly mineral fertilizers, which have typically an efficiency of less than 40\%. After decades of searching for a practical tool to estimate the N mineralization capacity of soil, there is still no consistent methodology. This PhD aimed to assess routinely analyzed soil parameters, different physical and chemical fractions of soil organic matter (SOM) and lastly enzyme activities as predictors for the net N mineralization in Bangladeshi paddy soils. Soils were collected from 25 farmers{\textquoteright} fields and two long term field experiments on contrasting soil types, namely on a highly weathered {\textquoteleft}terrace soil{\textquoteright} and on a younger {\textquoteleft}floodplain soil{\textquoteright}. Fertilizer management had a significant but contrasting impact on soil N mineralization within both long-term experiments. Bio-availability of N increased in the terrace soil experiment with increasing soil N content, logically in relation to application of fertilizers and organic amendments. On the contrary there was a relatively stronger stabilization of soil N against anaerobic mineralization with higher paddy soil N and C contents in the floodplain experiment and in the set of farmers{\textquoteright} fields. We further investigated SOM quality through physicochemical fractionation of the SOM. In the terrace soils experiment some of the physicochemical SOM fractions were found useful predictors for both aerobic and anaerobic N mineralization. However, none qualified as predictor of anaerobic N mineralization for the floodplain experiment and the set of farmers{\textquoteright} fields. An novel fractionation procedure with sub-critical water extraction yielded a similar limited outcome as for none of the isolated subcritical water extracts the N contents correlated with the anaerobic N mineralization rate. Finally we measured three enzyme activities relevant to N cycling in soil and all were found to be significantly influenced by management. Over all investigated soil parameters in this PhD research L-glutaminase activity was found to be the most useful predictor for the anaerobic N mineralization rate.},
  author       = {Kader, MD Abdul},
  isbn         = {9789059895133},
  language     = {eng},
  pages        = {IX, 213},
  publisher    = {Ghent University. Faculty of Bioscience Engineering},
  school       = {Ghent University},
  title        = {Nitrogen mineralization in subtropical paddy soils in relation to soil properties, organic matter fractions, and fertilizer management},
  year         = {2012},
}

Chicago
Kader, MD Abdul. 2012. “Nitrogen Mineralization in Subtropical Paddy Soils in Relation to Soil Properties, Organic Matter Fractions, and Fertilizer Management”. Ghent, Belgium: Ghent University. Faculty of Bioscience Engineering.
APA
Kader, M. A. (2012). Nitrogen mineralization in subtropical paddy soils in relation to soil properties, organic matter fractions, and fertilizer management. Ghent University. Faculty of Bioscience Engineering, Ghent, Belgium.
Vancouver
1.
Kader MA. Nitrogen mineralization in subtropical paddy soils in relation to soil properties, organic matter fractions, and fertilizer management. [Ghent, Belgium]: Ghent University. Faculty of Bioscience Engineering; 2012.
MLA
Kader, MD Abdul. “Nitrogen Mineralization in Subtropical Paddy Soils in Relation to Soil Properties, Organic Matter Fractions, and Fertilizer Management.” 2012 : n. pag. Print.