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Symbiotic Nitrogen Fixation of White Clover in a Mixed Sward is not Limited by Height of Repeated Cutting
Author(s) -
Seresinhe T.,
Hartwig U. A.,
Kessler W.,
Nosberger J.
Publication year - 1994
Publication title -
journal of agronomy and crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.095
H-Index - 74
eISSN - 1439-037X
pISSN - 0931-2250
DOI - 10.1111/j.1439-037x.1994.tb00179.x
Subject(s) - monoculture , nitrogen fixation , trifolium repens , nitrogen , agronomy , perennial plant , biology , field experiment , chemistry , organic chemistry
The aim of this study was to investigate whether symbiotic nitrogen fixation in white clover nodules limits nitrogen supply and hence clover growth by repeated defoliation at two cutting heights. Other possible factors governing symbiotic nitrogen fixation in the field were also elucidated. Using 15 N, a 2‐year field experiment including white clover ( Trifolium repens L. cv. Ladino) and perennial ryegrass ( Loliumperenne L. cv. Bastion) in monocultures and in mixtures was conducted in Eschikon, Switzerland. The effect of two cutting heights (4 cm and 10 cm above ground level) on the performance of symbiotic nitrogen fixation of white clover in the different sward‐types was investigated. After each harvest, the plots were fertilized with 3 g N m ‐2 (equivalent to 30 kg N ha ‐1 cut ‐1 or 210 kg N ha ‐1 year ‐1 ). In both years, white clover grown in a mixture with grass received a significantly higher percentage of nitrogen from symbiotic fixation compared with clover grown in monoculture. This phenomenon is attributed to the strong competitiveness of ryegrass in soil nitrogen uptake. Consequently, white clover in the clover‐ryegrass mixture was more dependent on symbiotic nitrogen fixation than that grown in monoculture. The cutting height did not preferentially influence symbiotic nitrogen fixation, as opposed to the uptake of mineral nitrogen from the soil. From this finding it is suggested that symbiotic nitrogen fixation did not limit the supply of nitrogen to clover and hence its growth. It is proposed that symbiotic nitrogen fixation in white clover is regulated by the demand for nitrogen rather than by the availability of carbohydrate reserves in the stolons. Symbiotic nitrogen fixation should thus be looked upon as an integrated plant growth factor and not as an isolated phenomenon.