Soil spatial variability and symbiotic nitrogen fixation by legumes

Journal Article · Sat Sep 01 00:00:00 EDT 1990 · Soil Science; (United States)

DOI:https://doi.org/10.1097/00010694-199009000-00003· OSTI ID:5327242

Reichardt, K ^[1]

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1. Univ. of Sao Paulo (Brazil)

The isotope dilution method for the estimation of N{sub 2} fixation by legumes is analyzed, comparing the application of {sup 15}N-enriched fertilizer with {sup 15}N-labeled soil. Soil variability of other dynamic processes in the soil are discussed in light of the distribution of the {sup 15}N label in the system. Field data were collected along six transects, 45 m long, with 30 plots (replicates) each. The legume (Vicia faba L.) was used as a fixing crop, barley (Hordeum vulgare L.) and oil radish (Raphinus sativus L.) as nonfixing standard crops. Isotope methods were also compared with the yield difference method. Results show that isotope methods were very sensitive to the distribution of the label in the soil and that dynamic processes involving N can significantly affect this distribution over a whole field. Best results were obtained with {sup 15}N-labeled soil. The particular site used, having been farmed for more than 20 years with {sup 15}N trials, showed a homogeneous residual {sup 15}N label that made it possible to estimate N{sub 2} fixation without the application of extra label. Estimates of N{sub 2} fixation with the isotope method were well correlated with the yield difference method when fertilizer use efficiency of the fixing and nonfixing crops were similar. Results also indicate that a good reference crop for one method might not be the best for the other method, and one reason for this is the variability of soil parameters and of dynamic processes occurring in the soil.

• OSTI ID: 5327242
• Journal Information: Soil Science; (United States), Vol. 150:3; ISSN 0038-075X
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
LEGUMINOSAE
NITROGEN FIXATION
SOILS
VARIATIONS
FERTILIZERS
ISOTOPE DILUTION
NITROGEN 15
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MAGNOLIOPHYTA
MAGNOLIOPSIDA
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
PLANTS
STABLE ISOTOPES
TRACER TECHNIQUES
540211* - Environment
Terrestrial- Basic Studies- Radiometric Techniques- (1990-)