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Microbial nitrogen dynamics in south central Chilean agricultural and forest ecosystems located on an Andisol

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Biotechnology for a sustainable economy (Bio-Economy)
Abstract
The natural soil N supply in volcanic soils (Andisols) can be a significant source of plant-available N for agro-ecosystems. Nevertheless, intensive farming systems in south Chile apply high fertilization rates, which lead to high production costs and involve a risk for adverse ecosystem effects. In order to achieve sustainable land management, a better understanding of the processes that govern soil N availability and loss, and their external drivers, is required. In this study, we selected a winter-cropland, a summer crop-winter fallow rotation, and a forest, used as a reference ecosystem. Gross N transformations ((15)N isotope dilution) and microbial community structure (phospho-lipid fatty acid analysis) in the topsoil were determined. Gross N mineralization was about ten times lower in the agro-ecosystems than in the forest, while gross nitrification was low in all sites. Gross N immobilization equalized or exceeded the gross inorganic N production in all sites. Microbial biomass was 3-5 times more abundant in the forest than in the agro-ecosystems. A positive relationship between the ratio fungi/bacteria and total microbial biomass was observed in these Andisols. We suggest that the reduction in fungal biomass induced a lower extracellular enzyme production and limited soil organic matter depolymerisation in the agro-ecosystems. We conclude that soil N cycling was unable to provide a significant N input for the croplands, but also the risk for ecosystem N losses was low, even under fallow soil conditions. Current fertilization practices appropriately anticipated the soil N cycling processes, but further research should indicate the potential of alternative land management to reduce fertilizer cost.
Keywords
(15)N isotope dilution, Andisol, Phospho-lipid fatty acid (PLFA), Fungi, Chile, Cropland, EXTRACTABLE ORGANIC-MATTER, VOLCANIC ASH SOILS, COMMUNITY STRUCTURE, PYROLYSIS GC/MS, FIXED AMMONIUM, ELEVATED CO2, MINERALIZATION, CARBON, NITRIFICATION, BIOMASS

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Citation

Please use this url to cite or link to this publication:

Chicago
Huygens, Dries, Dries Roobroeck, Lynn Cosyn, Francisco Salazar, Roberto Godoy, and Pascal Boeckx. 2011. “Microbial Nitrogen Dynamics in South Central Chilean Agricultural and Forest Ecosystems Located on an Andisol.” Nutrient Cycling in Agroecosystems 89 (2): 175–187.
APA
Huygens, Dries, Roobroeck, D., Cosyn, L., Salazar, F., Godoy, R., & Boeckx, P. (2011). Microbial nitrogen dynamics in south central Chilean agricultural and forest ecosystems located on an Andisol. NUTRIENT CYCLING IN AGROECOSYSTEMS, 89(2), 175–187.
Vancouver
1.
Huygens D, Roobroeck D, Cosyn L, Salazar F, Godoy R, Boeckx P. Microbial nitrogen dynamics in south central Chilean agricultural and forest ecosystems located on an Andisol. NUTRIENT CYCLING IN AGROECOSYSTEMS. 2011;89(2):175–87.
MLA
Huygens, Dries, Dries Roobroeck, Lynn Cosyn, et al. “Microbial Nitrogen Dynamics in South Central Chilean Agricultural and Forest Ecosystems Located on an Andisol.” NUTRIENT CYCLING IN AGROECOSYSTEMS 89.2 (2011): 175–187. Print.
@article{2036023,
  abstract     = {The natural soil N supply in volcanic soils (Andisols) can be a significant source of plant-available N for agro-ecosystems. Nevertheless, intensive farming systems in south Chile apply high fertilization rates, which lead to high production costs and involve a risk for adverse ecosystem effects. In order to achieve sustainable land management, a better understanding of the processes that govern soil N availability and loss, and their external drivers, is required. In this study, we selected a winter-cropland, a summer crop-winter fallow rotation, and a forest, used as a reference ecosystem. Gross N transformations ((15)N isotope dilution) and microbial community structure (phospho-lipid fatty acid analysis) in the topsoil were determined. Gross N mineralization was about ten times lower in the agro-ecosystems than in the forest, while gross nitrification was low in all sites. Gross N immobilization equalized or exceeded the gross inorganic N production in all sites. Microbial biomass was 3-5 times more abundant in the forest than in the agro-ecosystems. A positive relationship between the ratio fungi/bacteria and total microbial biomass was observed in these Andisols. We suggest that the reduction in fungal biomass induced a lower extracellular enzyme production and limited soil organic matter depolymerisation in the agro-ecosystems. We conclude that soil N cycling was unable to provide a significant N input for the croplands, but also the risk for ecosystem N losses was low, even under fallow soil conditions. Current fertilization practices appropriately anticipated the soil N cycling processes, but further research should indicate the potential of alternative land management to reduce fertilizer cost.},
  author       = {Huygens, Dries and Roobroeck, Dries and Cosyn, Lynn and Salazar, Francisco and Godoy, Roberto and Boeckx, Pascal},
  issn         = {1385-1314},
  journal      = {NUTRIENT CYCLING IN AGROECOSYSTEMS},
  keyword      = {(15)N isotope dilution,Andisol,Phospho-lipid fatty acid (PLFA),Fungi,Chile,Cropland,EXTRACTABLE ORGANIC-MATTER,VOLCANIC ASH SOILS,COMMUNITY STRUCTURE,PYROLYSIS GC/MS,FIXED AMMONIUM,ELEVATED CO2,MINERALIZATION,CARBON,NITRIFICATION,BIOMASS},
  language     = {eng},
  number       = {2},
  pages        = {175--187},
  title        = {Microbial nitrogen dynamics in south central Chilean agricultural and forest ecosystems located on an Andisol},
  url          = {http://dx.doi.org/10.1007/s10705-010-9386-0},
  volume       = {89},
  year         = {2011},
}

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