The allelopathic potential of the species of genus Sorghum [Grain sorghum (Sorghum bicolor L.); Sweet sorghum (Sorghum bicolor var. saccharatum); Broom millet (Sorghum bicolor var. technicum); Sudan grass (Sorghum sudanense(Piper.) Stapf) and Johnson grass (Sorghum halepense (L.) Pers.)] was studied under laboratory conditions. The so-called sandwich method was used, and as an acceptor – Lettuce (Lactuca sativa L.). Rhizosphere soil was used as the carrier of the allelochemicals from the donors as well as dry root and above-ground biomass.
The allelopathic potential was determined by a composite indicator development index (GI), according to which species of the genus Sorghum can be provisionally arranged in the following descending order: S. bicolor var. technicum→ S. halepense → S. bicolor var. saccharatum→ S. sudanense → S. bicolor. The carriers of the аllelochemicals, regardless of the donors and concentrations, inhibited the development of swear in the recipient by 30.5% – in the rhizosphere soil; by 35.9% – in the dry root biomass and by 47.2% – in the dry above-ground biomass respectively. It was found that with the increasing concentrations (0.2; 0.4; 0.8 and 1.6% w/v) the recipient seed germination was suppressed as follows: in the rhizosphere soil – from 4.8 to 86.7%, in the dry above-ground biomass – from 13.9 to 81.9% and in the dry root biomass – from 13.9 to 55.3%, compared with the controls.
The results indicated the possibility for some species of the genus Sorghum to be used as components in future breeding programmes, as well as an alternative for weed control in organic production. Their allelopathic potential and multifunctional application (for food, pharmaceutical and industrial purposes) defines them as promising crops in building a balanced crop rotations in organic farming or their inclusion as intermediate crops.