Differential Allelopathic Potential of Three Cereal Species

Abstract

Barley is an important cereal cultivated in Tunisia for double purpose, grazing and grain production. Barley is mostly conducted in monoculture or in rotations with other cereals such bread wheat and specially durum wheat. When conducted in direct drilling (DD), residues (stubble, straw) are abandoned on soil surface which could be a source of allelochemicals that may express auto-toxicity or hetero-toxicity detrimental to the yields of a following crop. The differential allelopathic potential of three cereal (barley, bread wheat, durum wheat) mulches and soils cultivated with these cereals was studied, using bioassays (germination, seedling growth). For all bioassays 'Manel' (barley) was the testvariety. Radicle growth bioassay was the most sensitive test to detect allelopathy expressed in the form of auto-toxicity (barley/barely) or hetero-toxicity (bread wheat/barley, durum wheat/barley). Only soilextracts cultivated with bread wheat, showed a significant effect on barley growth. A differential inhibitory effect was identified within and between studied cereal species. Hetero-toxicity was significantly more pronounced than auto-toxicity. Moreover, stubble-extracts were more inhibitory than straw-extracts independently of cereal species. Results suggest that barley auto-toxicity and bread and durum wheats hetero-toxicity should be considered when applying crop sequencing especially in conservation agriculture (CA) using DD on permanent mulch. Barley monoculture appeared to be a better choice than a rotation of barley with bread or durum wheat.

Keywords

• Allelopathy
• auto-toxicity
• barley
• bread wheat
• durum wheat
• hetero-toxicity
• residues