Differential autotoxicity of five cropped barley varieties. Oueslati, O. and Ben-Hammouda, M. (Tunisia)

Abstract

Field experiments were conducted in the North-West semi-arid zone of Tunisia during two consecutive growing seasons (2002/03, 2003/04) to study: (i) the differential auto-toxicity/allelopathy expressed by five barley (Hordeum vulgare L.) varieties (‘Manel’, ‘Martin’, Moumtez’, ‘Rihane’, ‘Souihli’) residues (straw, stubble), used as mulch in direct drilling, (ii) the effect of soils cultivated with barley, and (iii) the impact of growing season in such auto-toxicity. The auto-toxic potential was assessed on germination and seedlings (coleoptile, radicle) growth bioassays, with ‘Manel’ as the test-variety. Radicle growth bioassay was the most sensitive test to detect barley auto-toxicity, when compared to coleoptile growth and germination bioassays. Barley residue-extracts showed a highly significant inhibitory effect on radicle growth of ‘Manel’ during the two growing seasons, with significant varietal differences. Unexpectedly, soil extracts were not active on germination and seedlings growth of barley. Stubble-extracts were more auto-toxic then those of straw, independently of variety and growing seasons. Among the five tested varieties, ‘Manel’ and 'Martin' were found as the most allelopathic and ‘Souihli’ as the least allelopathic one. Such results suggest a particular care in choosing the appropriate barley variety in monoculture under a direct drilling system. Moreover, the residues amount to be left on the soil surface must be reduced.

Keywords

• Allelopathy
• auto-toxicity
• barley
• bioassays
• growing season