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Clover N‐Fixation Measurement by Total‐N Difference and 15 N A‐Values in Lysimeters 1
Author(s) -
Williams W. A.,
Jones M. B.,
Delwiche C. C.
Publication year - 1977
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1977.00021962006900060029x
Subject(s) - loam , lysimeter , agronomy , trifolium subterraneum , legume , mathematics , bromus , fixation (population genetics) , significant difference , fertilizer , field experiment , zoology , biology , environmental science , soil water , poaceae , soil science , pasture , biochemistry , statistics , gene
Assessment and improvement of N fixation by legumes on annual‐type range is becoming increasingly important in light of the increasing need for energy conservation. A comparison was made of two methods of assessing N fixation: a simple but crude method by measuring the total‐N difference in tops of an N‐fixing legume and a non N‐fixing grass, and a more expensive method using A‐values determined from 15 N applications to the same legume and grass species. Subterranean clover ( Trifolium subterraneum L.) and soft chess grass ( Bromus molis L.) were grown in field lysimeters (69 cm deep by 36 cm diam.) filled with Josephine loam (Typic Haplozerults, fine loamy, mixed mesic) for 3 years. Single (100 and 500 kg/ha) and repeated (100 kg/ha) applications of 15 N were made and determinations were made of soil and fertilizer N in the plants, soil, and leachate periodically. The relation between the two methods was strongly linear; fixation (kg/ha) by the A‐value method = 50.1 + 0.852 N fixation by difference (r = 0.98, n = 15). Consequently, previous values cited for N fixation measured by the difference method for winter annual legumes in California may have been underestimated by about 40%.