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Assessment of N2 fixation by pasture legumes on the Central Plateau of Tasmania
thesisposted on 2023-05-26, 22:07 authored by Lane, PA
The acetylene reduction (AR) assay and a N dilution technique have been used to estimate N2 fixation by temperate pasture legumes growing in association with grasses under field conditions at two sites on the Central Plateau of Tasmania. An in situ approach which avoided intensive and destructive sampling was developed for conducting routine. AR assays. Using this approach seasonal and diurnal patterns of ni trogenase activity were determined for two clovers, Trifol i um ambiguum M.bieb. and T. repens L., at one site (Stone Hut ) and for T. repens at a second site (Penstock). The seasonal pattern of nitrogenase activity followed closely the general growth pattern of the clovers. Nitrogenase activity was very low from late autumn to early spring as a result of low temperature (< 5 ¬¨‚àû C), but increased rapidly to be at maximum levels during late spring and early summer. Activity declined to a low level in mid-summer which coincided with low soil moisture content. There was a second but much smaller peak of activity in autumn as soil moisture conditions improved, and before the onset of winter temperatures. Severe defoliation of relatively mature plants caused a reduction in ni trogenase activity and, combined with low soil moisture conditions, delayed considerably the recovery, of activity. Diurnal variation in nitrogenase activity was demonstrated for both species under natural field conditions. Overall these fluctuations were more closely related to soil than air temperature, and T. repens showed a more variable response to diurnal variation in environmental conditions than T. ambiguum.
Rights statementCopyright 1984 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s). Thesis (Ph.D.) - University of Tasmania, 1984. Bibliography: leaves 207-236