Longevity of seeds of four annual grass and two dicotyledon weed species as related to placement in the soil and straw disposal technique

Abstract

Persistence of seeds of the four winter annual grass species, Alopecurus myosuroides, Bromus sterilis, Bromus hordeaceus and Vulpia myuros, were studied under field conditions. The studies also included the two dicotyledon species, Tripleurospermum inodorum and Galium aparine. Seed samples were stored in the field at different depths in the plough layer for a year. Following germination, seedling emergence was taken as an indicator of field persistence. In a supplementary investigation, seed samples were placed on the soil surface or buried at 2 cm for a month and then tested for viability. Persistence of the two Bromus species was very short, irrespective of depth and duration of burial. Persistence of the other species was positively correlated with incorporation of seeds to a few centimetres depth. Increasing the depth of incorporation below 2 cm had a variable influence on persistence. Persistence of seeds placed directly on the soil surface was short, whether they were left there for a year or a month. Whether seeds at the soil surface were left uncovered or covered with chopped straw had limited influence on seed persistence. However, straw cover significantly increased persistence of A. myosuroides seeds and there was the same tendency with T. inodorum.