Nutrient Cycling in Agroecosystems

, Volume 89, Issue 2, pp 175–187

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

  • Dries Huygens
  • Dries Roobroeck
  • Lynn Cosyn
  • Francisco Salazar
  • Roberto Godoy
  • Pascal Boeckx
Original Article

DOI: 10.1007/s10705-010-9386-0

Cite this article as:
Huygens, D., Roobroeck, D., Cosyn, L. et al. Nutr Cycl Agroecosyst (2011) 89: 175. doi:10.1007/s10705-010-9386-0

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 (15N 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

Andisol 15N isotope dilution Phospho-lipid fatty acid (PLFA) Fungi Chile Cropland 

Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • Dries Huygens
    • 1
    • 2
  • Dries Roobroeck
    • 1
  • Lynn Cosyn
    • 1
  • Francisco Salazar
    • 3
  • Roberto Godoy
    • 4
  • Pascal Boeckx
    • 1
  1. 1.Laboratory of Applied Physical Chemistry, ISOFYS, Faculty of Bioscience EngineeringGhent UniversityGhentBelgium
  2. 2.Institute of Soil Science and Agricultural Engineering, Faculty of Agricultural SciencesUniversidad Austral de ChileValdiviaChile
  3. 3.National Institute for Agricultural Research, INIA-ChileOsornoChile
  4. 4.Institute of Botany, Faculty of SciencesUniversidad Austral de ChileValdiviaChile

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