Longevity of seeds of Poa trivialis and Vulpia myuros as affected by simulated soil tillage practices and straw disposal technique

In grass-seed production, the purity of the product is of high importance and a main issue in an integrated strategy is to reduce or eliminate the seedbank of species which are both difficult or impossible to control in a future grass-seed crop, and also difficult to separate from the cultivated species. This study investigated the influence of different simulated soil-tillage practices on persistence of seeds of the two grass species, Poa trivialis and Vulpia myuros, under field conditions. Leaving seeds of the two species at the soil surface reduced the survival of seeds to low levels compared with strategies that involved incorporation of the seeds shortly after seed-shedding. Persistence of P. trivialis seeds increased with increasing depth of incorporation whereas this relationship was more variable for V. myuros. It was concluded that soil-tillage strategies that leave the seeds at the soil surface for 1-2 months reduced the survival of seeds of the two species to low levels compared with strategies that involved a deep incorporation of the seeds shortly after seed-shedding. The study also investigated the possibilities of using the stale seedbed technique to reduce the seedbank of these two species in the autumn ahead of a spring-established grass-seed crop. This method was found to be very effective in reducing the potential risk of contamination from this source. Finally, the study confirmed that P. trivialis has very persistent seeds whereas the persistence of seeds of V. myuros is limited.