Development of a thermal-time model for combinational dormancy release of hairy vetch (Vicia villosa ssp. villosa)

RENZI, JUAN PABLO; CHANTRE, GUILLERMO RUBÉN; CANTAMUTTO, MIGUEL A.

CROP & PASTURE SCIENCE

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2014 vol. 65 p. 470 - 478

1836-5795

Seed dormancy could be a factor related to natural reseeding of hairy vetch (Vicia villosa ssp. villosa), a winter annual species cultivated for seed, pasture, hay, green manure and cover crop. The presence of combinational dormancy (physical + physiological = PY + PD) in hairy vetch was explored by a model using laboratory and field measures. At the stage of natural dispersal, dry seeds of hairy vetch were stored under laboratory conditions at 5, 10, 20 and 30°C (± 2°C) or buried at 5 cm depth in the experimental field. Germination at 5, 8, 10, 15, 20 and 25°C was assessed at regular intervals up to 295 days after harvest. Following the hypothesis of the existence of a combinational (PY+PD) dormancy mechanism, model development was based on the estimation of: (i) the fraction of non-PY dormant seed as a function of after-ripening thermal time accumulation, and (ii) seed population thermal parameters associated to a given level of physiological dormancy. The developed model adequately described the after-ripening thermal time requirements for combinational dormancy release of V. villosa. Based on model predictions, under a semiarid thermal regime, more than 45% of vetch seed shed during the summer season would be able to germinate during early autumn. Thus, the seed-bank size threshold at the end of the first growing season should be over 65 seed.m-2 in order to reach a minimum stand of 30 plants.m-2 necessary for a productive pasture.