Variation in the symbiotic nitrogen fixation rates of three Lotus species as affected by cut and grazing.

Emilio Ruz J.1, Hernán Acuña P., Erick Zagal V., Leticia Barrientos D. y Andrea Pincheira P.

Symbiotic N fixation by three legume species of genus Lotus: L. corniculatus, L. tenuis and L. uliginosus, was evaluated under cutting and grazing conditions in heavy soils (Typic Pelloxererts) of the main rice cropping area of Chile. A completely randomized split-plot experimental design with four replications was used which evaluated three heights (3, 6and 9 cm) and two cut frequencies (6 and 8 weeks). The grazing experiment used Hereford animals. Considerable amounts ofN: 219.4; 193.3 and 181.0 kg ha-1 for L. corniculatus, L. tenuis and L. uliginosus, respectively, were found in the cut experiment, whereas the values determined for the same species in the grazing experiment reached 173.0; 123.2 and 111.9 kg ha-1 , respectively. It is concluded that these Lotus species are active fixers of N. The highest rates ofN fixation were observed for a frequency of 6 weeks and a cut height ofthree centimetres.

Key words: symbiotic fixation, acethylene reduction assay, L. corniculatus, L. tenuis, L. uliginosus.

1 Instituto de Investigaciones Agropecuarias, Centro Regional de Investigación Quilamapu, Casilla 426, Chillán, Chile. E-mail: eruz@inia.cl.

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