Qualitative and quantitative content of soil weed seed bank in sunflower crop

Abstract

Soil contains great amount of seeds of different weed species. The term "seed bank" refers to the reservoir of seed capable of germinating in favorable conditions in the soil or on the surface. Determination of the seed bank is of great sig-nificance for study of population dynamics, as well as for planned weed control. Data on seed quantity in certain area enable better choice of crops and cultural practices, as well as more rational herbicide use. During 2008-2009 studies of the seed bank in sunflower crop were performed in two different localities with the aim of determination of quantitative and qualitative properties of the seed bank and viability of seeds from arable soil layers of 0-10; 10-20 and 20-30 cm. Samples of the soil were taken before the end of vegetation, from each plot in four replications. The samples were rinsed in the water through copper sieves of specific diameters, and weed seeds were separated. Seed was germinated in controlled conditions of climatic chamber. Germination capability and hypocotyls and epicotyls lengths of seedlings were evaluated after 14 days. Seeds de-termined from the studied samples showed a great diversity but only a few of them were dominant, i.e. were more abundant in seed, such as: Amaranthus retroflexus, Sinapis arvensis, Polygonum lapathifolium and Datura stramonium. The species Sinapis arvensis, Polygonum lapathifolium, Hibiscus trionum, Amaranthus retroflexus, Echinocloa crus-galli and Datura stramonium, which were the species whose seed proved to be dominant in all of the examined soil samples had the greatest percentage of viable seeds. The highest level of germination viability was found in seed of Polygonum lapathifolium, Datura stramonium and Sinapis arvensis.