High rates of nitrogen cycling in volcanic soils from Chilean grasslands

A - Papers appearing in refereed journals

Dixon, E. R., Cardenas, L. M., Alfaro, M., Salazar, F. and Hatch, D. J. 2011. High rates of nitrogen cycling in volcanic soils from Chilean grasslands. Rapid Communications in Mass Spectrometry. 25 (11), pp. 1521-1526.

AuthorsDixon, E. R., Cardenas, L. M., Alfaro, M., Salazar, F. and Hatch, D. J.
Abstract

There are over one million hectares of pasture in Chile, and 80% and 50% of the country's milk and meat comes from 72% of this area, situated in the lake region of southern Chile. The soils are volcanic and a major characteristic is that they have very high organic matter (OM) contents with the potential to support plant growth with only moderate levels of added nitrogen (N). To understand better the potential fertility of these soils in order to maximise production and minimise losses of N, we undertook studies using the stable isotope of N ((15)N) to resolve the rates of the main internal N cycling processes in three soils representing the two main volcanic soil types: Osorno and Chiloe (Andisol) and Cudico (Ultisol). We also assessed the longer-term potential of these soils to sustain N release using anaerobic incubation. Gross rates (mu g N g(-1) day(-1)) of mineralisation were 27.9, 27.1 and 15.5 and rates of immobilisation were 5.9, 12.0 and 6.3 for Osorno, Chiloe and Cudico, respectively, implying high rates of net mineralisation in these soils. This was confirmed by anaerobic incubation which gave potential seasonal net mineralisation indices of 1225, 1059 and 450 kg N ha(-1) in the top 10 cm soil layers of the three soils. However, plant production may still benefit from added N, as the release of N from organic sources may not be closely synchronised with crop demand. The low rates of nitrification that we found with these acidic soils suggest that the more mobile N (viz. nitrate-N) would be in limited supply and plants would have to compete for the less mobile ammonium-N with the soil microbial biomass. Nitrogen was mineralised in appreciable amounts even down to 60 cm depth, so that leaching could become significant, particularly if the soils were limed, which could enhance nitrification and N mobility through the soil profile. Copyright (C) 2011 John Wiley & Sons, Ltd.

KeywordsBiochemical Research Methods; Chemistry, Analytical; Spectroscopy
Year of Publication2011
JournalRapid Communications in Mass Spectrometry
Journal citation25 (11), pp. 1521-1526
Digital Object Identifier (DOI)doi:10.1002/rcm.4969
PubMed ID21594925
Open accessPublished as non-open access
Funder project or codeSEF
North Wyke Research (NWR)
Developing a mechanistic understanding of biogenic gaseous emissions from the soil-plant system
ISSN09514198
0951-4198
PublisherWiley

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