The influence of digestion and storage in silage and organic manure on the germinative ability of six weed species (Papaver argemone, P. dubium, Legousia speculum-veneris, Centaurea cyanus, Spergula arvensis, Trifolium arvense)

A former analysis of organic manure in terms of seed contents failed to demonstrate the presence of seeds of rare weeds. The aim of the presented studies is to answer the question if germinable seeds of species like Papaver argemone L., P. dubium L., Legousia speculum-veneris (L.) Chaix., Centaurea cyanus L., Spergula arvensis L., Trifolium arvense L. could not be found because of being to rare to be sampled or because of their loss of germinative ability during storage or digestion. If the latter proves to be true such species won't get an additional chance of dispersal by manuring. First, germination rates of the six species were determined. Then seed lots filled in nylon bags were buried in stable and semi-liquid manure and in silage and stored three, six, nine or twelve months. Additionally, a feeding experiment with a cow was carried out. Without treatment germination rates varied between only 0.4 % and 76 % but each species showed a decrease when stored or fed. After six months storage in silage all species except Papaver dubium kept their germinative ability. Three months later Centaurea cyanus didn't germinate any more and after twelve months only Trifolium arvense seedlings emerged (germination rate after 12 months storage: 0.4 %; without storage: 26.4 %). Some Trifolium arvense seeds also stayed germinable after one year storage in semi-liquid and stable manure (germination rate: 0.6 % and 0.7 %, respectively) and even after digestion. Furthermore, only Spergula arvensis (germination rate after 3 months storage: 17.4 %; without storage: 75.4 %) and Papaver dubium (germination rate after 3 months storage: 0.2 %; without storage: 76 %) succeeded in germinating after being stored in semi-liquid manure for three months. The results show only a minute chance for Trifolium arvense to be dispersed by manuring but in general this farming operation needs not to be taken into account as dispersal agent for rare species.