Sunflower-desired allelopathic crop for sustainable and organic agriculture?

Sunflower listed as a crop species of high allelopathic activity with the potential of its exploitation as complementary to other practices for weed managements, has received recreantly increased attention. The aim of this chapter is to describe how genotypic variation, growing conditions, and various plant organs, such as leaves, stems and inflorescences may influence the allelopathic activity of sunflower. The allelopathic effects of sunflower can be both stimulatory and inhibitory and is manifested both against weeds and crops including sunflower - autotoxicity. Sunflower shows inhibitory effect on a relatively wide range of weeds and crops as assayed under laboratory, greenhouse and field conditions. It is believed that dicotyledonous weeds are more affected than grasses though, it is not always the case as four species of Poaceae family are quite susceptible. Sunflower allelopathy can be exploited in several ways, among others as biologically active much. It effectively reduces weeds infestation in the field with some being almost completely eliminated, including the troublesome in cereals of Central Europe - Apera spica-venti. However, it may also adversely affect crops. It is too early to propose a ready-to-use strategy for weed management employing allelopathy and more research activities are needed. Based on available in literature data and own research, some recommendations for overcoming the negative impact on crops are discussed here and future research lines are provided.