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Nitrogen Fixation by Alfalfa with Two Substrate Nitrogen Levels under Sodium Chloride Stress
Author(s) -
Zhou M.,
Tucker T. C.,
Pessarakli M.,
Cepeda J. A.
Publication year - 1992
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/sssaj1992.03615995005600050027x
Subject(s) - salinity , nitrogen fixation , chemistry , nitrogen , nutrient , cultivar , sodium , agronomy , chloride , cutting , medicago sativa , zoology , horticulture , biology , ecology , organic chemistry
Nitrogen fertilizer is rarely applied to alfalfa ( Medicago sativa L.) fields because high yields are attained with symbiotic N 2 fixation between alfalfa and Rhizobium meliloti . The growth and N 2 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 NO 3 ‐N L −1 was used during the growth at first cutting and 1 mg NO 3 ‐N L −1 was provided for the regrowth of the second cutting. A second N 2 ‐fixation study was conducted with two salt levels (0 and −0.6 MPa added OP) and two NO 3 ‐N levels (1 and 5 mg L −1 ). The NaCl salinity resulted in substantial reductions in growth, N 2 fixation percentage, and total fixed N 2 . The effect of salinity was more pronounced for the second cuttings than the first ones. The percentages of total N 2 fixed by plants were substantially decreased by increasing NO 3 ‐N level in the nutrient solution and the reduction was enhanced as the growth period progressed. The amount of fixed N 2 , however, did not decrease with increasing NO 3 ‐N availability. Fixed N 2 was between 86 and 93% for the 1 mg NO 3 ‐N L −1 level in the nutrient solution, whereas this value ranged between 50 and 60% for the 5 mg NO 3 ‐N L −1 level. The alfalfa cultivar and the selections did not differ in either growth or N 2 fixation. The combination of high NO 3 ‐N level and salinity, however, significantly decreased the percentage of fixed N 2 in the plants.