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Influence of Available Nitrogen and Rice Genotype on Associative Dinitrogen Fixation
Author(s) -
Malarvizhi P.,
Ladha J. K.
Publication year - 1999
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1999.03615995006300010015x
Subject(s) - soil water , oryza sativa , nitrogen fixation , nitrogen , isotope dilution , agronomy , chemistry , growing season , biology , environmental science , soil science , mass spectrometry , biochemistry , organic chemistry , chromatography , gene
Rice ( Oryza sativa L.) genotypes with a high ability to support biological N 2 fixation are of interest because they would enhance N gains in the rice‐soil system without changing existing cultural practices. Pot experiments were conducted in a greenhouse during the 1994 wet season to determine the amount of N 2 derived from the atmosphere (Ndfa) by 10 rice genotypes grown in three soils with varying levels of initial soil‐NH + 4 ‐N. Enriched 15 N and natural abundance δ 15 N dilution methods were employed. Flooded soils were puddled with and without 99.5 atom 15 N%‐labeled urea to minimize spatial variation of the isotope. The integrated 15 N enrichment of plant available N, calculated using a model that accounts for temporal changes in the isotopic composition, was used as a reference to estimate genotypic differences in Ndfa. The 15 N enrichment of soil available N declined exponentially and was half the original level at 122 d. The δ 15 N values correlated with atom 15 N% excess of enriched 15 N for the rice genotypes grown in two out of three soils. Percentage Ndfa for the genotypes across three soils ranged from 4.2 to 32.2 when calculated using as a reference plant, and from 10.8 to 35.9 when calculated using 15 N enrichment of soil available N as a reference. Genotypic differences were significant and more pronounced at low soil‐NH + 4 ‐N (11 mg kg ‐1 ) than at higher soil‐NH + 4 ‐N (79 and 92 mg kg ‐1 ); they ranged from 14.9 to 35.9% at low N and from 10.8 to 23.6% at high N. Some genotypes consistently gave either high or low Ndfa. Because of the low levels and narrow range of genetic differences in associative N 2 fixation, the potential for its improvement through breeding appears to be limited.