HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Zhou, M. Articles by Cepeda, J. A. Search for Related Content PubMed Articles by Zhou, M. Articles by Cepeda, J. A. Agricola Articles by Zhou, M. Articles by Cepeda, J. A.

Nitrogen Fixation by Alfalfa with Two Substrate Nitrogen Levels under Sodium Chloride Stress

Contribution from the Dep. of Soil and Water Science, Univ. of Arizona, Tucson, AZ 85721

* Corresponding author.

ABSTRACT

Nitrogen fertilizer is rarely applied to alfalfa (Medicago sativa L.) fields because high yields are attained with symbiotic N₂ fixation between alfalfa and Rhizobium meliloti. The growth and N₂ fixation by one alfalfa cultivar with low salt tolerance (‘Mesa-sirsa 83CL’) and two selections that are salt tolerant at germination (‘Mesa-sirsa Cycle 3’ and ‘Cycle 5’) were investigated at four NaCl salinity levels (0, –0.3, –0.6, and –1.2 MPa added osmotic potentials, OP) in a greenhouse. Automatically recirculated nutrient solution with 5 mg NO₃-N L^–1 was used during the growth at first cutting and 1 mg NO₃-N L^–1 was provided for the regrowth of the second cutting. A second N₂-fixation study was conducted with two salt levels (0 and –0.6 MPa added OP) and two NO₃-N levels (1 and 5 mg L^–1). The NaCl salinity resulted in substantial reductions in growth, N₂ fixation percentage, and total fixed N₂. The effect of salinity was more pronounced for the second cuttings than the first ones. The percentages of total N₂ fixed by plants were substantially decreased by increasing NO₃-N level in the nutrient solution and the reduction was enhanced as the growth period progressed. The amount of fixed N₂, however, did not decrease with increasing NO₃-N availability. Fixed N₂ was between 86 and 93% for the 1 mg NO₃-N L^–1 level in the nutrient solution, whereas this value ranged between 50 and 60% for the 5 mg NO₃-N L^–1 level. The alfalfa cultivar and the selections did not differ in either growth or N₂ fixation. The combination of high NO₃-N level and salinity, however, significantly decreased the percentage of fixed N₂ in the plants.

as Journal article no. 7236.

Received for publication April 7, 1990.