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Is there a link between reduction of Fe and Mn and anaerobic N mineralization in floodplain paddy soils in Bangladesh?

Author
Organization
Project
VLIR-ICP-PhD scholarship Masuda Akter
Abstract
The N mineralization in wetland paddy soils is influenced by a multitude of physicochemical factors. Previous experimental work revealed no relationship at all between anaerobic soil N mineralization and mineralogy or soil organic matter composition in Bangladeshi young floodplain paddy soils. We therefore hypothesized that the anaerobic biological activity in these soils instead depends on availability of alternative electron acceptors. We hypothesized reducible Fe3+ and Mn4+ content to determine anaerobic SOM mineralization and thereby NH4+ release in soils from Northern Bangladesh. We compared NH4 and soil solution parameters in incubated soil collected from field experimental plots and farmers’ fields. We assessed the influence of Fe and Mn application on anaerobic N mineralization in lab incubation experiments. Finally, we investigated the contribution of abiotic release of fixed NH4+ on mineral N production relative to biotic anaerobic N mineralization. Soils were collected, firstly from five fertilizer application treatments (Control, N, NP, NPK and N+FYM) from a long-term field experiment with double rice cropping at the Bangladesh Agricultural University (BAU) and secondly from four farmers’ paddy fields. All soils were either treated with Fe2O3 (T2), Mn/Al mixed oxides (T3) or were left untreated (T1) and were anaerobically incubated. pH, Fe, Mn and dissolved OC in soil solution were followed by use of rhizon moisture samplers and produced CH4 and CO2 were measured at a regular interval. The KCl-extractable NH4+, microbial biomass carbon (MBC) and pH-KCl at the end of the experiment were also determined. Generally, over all five fertilizer treatments there were no considerable differences in soil solution Fe and Mn concentrations between T1 and T2 treatments. The KCl extractable NH4+ content increased by 12 to 37 mg kg-1 after 8 weeks, but the differences among the Fe or Mn treated and untreated soils were insignificant. For the four studied farmers’ fields The NH4+ release patterns were asymptotic with no differences among the treatments (T1, T2 and T3). The total NH4+ released ranged from 25 to 54 mg kg-1 during 10 weeks of anaerobic incubation. The results indicated that the availability of Mn4+ and Fe3+ did not have any effect on anaerobic N mineralization. Rather, application of amorphous Mn-oxides merely retarded Fe dissolution and CH4 production. Finally, non-exchangeable (i.e. fixed) NH4+-N and MBC of anaerobically incubated untreated farmers’ fields soils were measured. The amount of non-exchangeable NH4+-N differed significantly among the four soils and increased significantly after 2 and 4 weeks of flooding. In all soils, the MBC already reached a maximum after 2 weeks of flooding (0.6 to 2.3% of total SOC), in close correspondence to the fast rise in exchangeable NH4+ after flooding. We conclude that the exchangeable NH4 in these farmers’ fields paddy soils is mainly derived from anaerobic N mineralization and not from the release of fixed-NH4+.
Keywords
electron acceptors, Paddy soil

Citation

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Chicago
Sleutel, Steven, Masuda Akter, Mohammed Abdul Kader, Shamim Ara Begum, and Stefaan De Neve. 2014. “Is There a Link Between Reduction of Fe and Mn and Anaerobic N Mineralization in Floodplain Paddy Soils in Bangladesh?” In Paddy Soils International Workshop, Abstracts, 17–17.
APA
Sleutel, Steven, Akter, M., Kader, M. A., Begum, S. A., & De Neve, S. (2014). Is there a link between reduction of Fe and Mn and anaerobic N mineralization in floodplain paddy soils in Bangladesh? Paddy Soils international workshop, Abstracts (pp. 17–17). Presented at the Paddy Soils international workshop: Biogeochemistry of submerged agro-ecosystems : properties, processes, cycles and functions.
Vancouver
1.
Sleutel S, Akter M, Kader MA, Begum SA, De Neve S. Is there a link between reduction of Fe and Mn and anaerobic N mineralization in floodplain paddy soils in Bangladesh? Paddy Soils international workshop, Abstracts. 2014. p. 17–17.
MLA
Sleutel, Steven, Masuda Akter, Mohammed Abdul Kader, et al. “Is There a Link Between Reduction of Fe and Mn and Anaerobic N Mineralization in Floodplain Paddy Soils in Bangladesh?” Paddy Soils International Workshop, Abstracts. 2014. 17–17. Print.
@inproceedings{5822004,
  abstract     = {The N mineralization in wetland paddy soils is influenced by a multitude of physicochemical factors. Previous experimental work revealed no relationship at all between anaerobic soil N mineralization and mineralogy or soil organic matter composition in Bangladeshi young floodplain paddy soils. We therefore hypothesized that the anaerobic biological activity in these soils instead depends on availability of alternative electron acceptors. We hypothesized reducible Fe3+ and Mn4+ content to determine anaerobic SOM mineralization and thereby NH4+ release in soils from Northern Bangladesh. We compared NH4 and soil solution parameters in incubated soil collected from field experimental plots and farmers{\textquoteright} fields. We assessed the influence of Fe and Mn application on anaerobic N mineralization in lab incubation experiments. Finally, we investigated the contribution of abiotic release of fixed NH4+ on mineral N production relative to biotic anaerobic N mineralization.
Soils were collected, firstly from five fertilizer application treatments (Control, N, NP, NPK and N+FYM) from a long-term field experiment with double rice cropping at the Bangladesh Agricultural University (BAU) and secondly from four farmers{\textquoteright} paddy fields. All soils were either treated with Fe2O3 (T2), Mn/Al mixed oxides (T3) or were left untreated (T1) and were anaerobically incubated. pH, Fe, Mn and dissolved OC in soil solution were followed by use of rhizon moisture samplers and produced CH4 and CO2 were measured at a regular interval. The KCl-extractable NH4+, microbial biomass carbon (MBC) and pH-KCl at the end of the experiment were also determined.
Generally, over all five fertilizer treatments there were no considerable differences in soil solution Fe and Mn concentrations between T1 and T2 treatments. The KCl extractable NH4+ content increased by 12 to 37 mg kg-1 after 8 weeks, but the differences among the Fe or Mn treated and untreated soils were insignificant. For the four studied farmers{\textquoteright} fields The NH4+ release patterns were asymptotic with no differences among the treatments (T1, T2 and T3). The total NH4+ released ranged from 25 to 54 mg kg-1 during 10 weeks of anaerobic incubation. The results indicated that the availability of Mn4+ and Fe3+ did not have any effect on anaerobic N mineralization. Rather, application of amorphous Mn-oxides merely retarded Fe dissolution and CH4 production.
Finally, non-exchangeable (i.e. fixed) NH4+-N and MBC of anaerobically incubated untreated farmers{\textquoteright} fields soils were measured. The amount of non-exchangeable NH4+-N differed significantly among the four soils and increased significantly after 2 and 4 weeks of flooding. In all soils, the MBC already reached a maximum after 2 weeks of flooding (0.6 to 2.3\% of total SOC), in close correspondence to the fast rise in exchangeable NH4+ after flooding. We conclude that the exchangeable NH4 in these farmers{\textquoteright} fields paddy soils is mainly derived from anaerobic N mineralization and not from the release of fixed-NH4+.},
  author       = {Sleutel, Steven and Akter, Masuda and Kader, Mohammed Abdul and Begum, Shamim Ara and De Neve, Stefaan},
  booktitle    = {Paddy Soils international workshop, Abstracts},
  keyword      = {electron acceptors,Paddy soil},
  language     = {eng},
  location     = {Freising, Germany},
  pages        = {17--17},
  title        = {Is there a link between reduction of Fe and Mn and anaerobic N mineralization in floodplain paddy soils in Bangladesh?},
  year         = {2014},
}