Submitted to: Journal of Agronomy and Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2004
Publication Date: 7/22/2005
Citation: Oueslati, O., Ben-Hammouda, M., Ghorbal, M.H., Guezzah, M., Kremer, R.J. 2005. Barley autotoxicity as influenced by varietal and seasonal variation. Journal of Agronomy and Crop Science. 191(4):249-254.
Interpretive Summary: Cereal crops are cultivated in many semi-arid regions of the world because they are adapted to low available soil water and high salt accumulation in soil. Because few other crops are adapted to such conditions, cereal crops are often grown continuously in the same fields. We previously showed that vegetative residues (i.e., straw) of some barley varieties that remained in the field suppressed the growth of the next crop planted in the same field, a condition known as autotoxicity. Because autotoxicity may be a consequence of environmental interactions, we examined growing season conditions in order to better understand the impact of autotoxicity on barley growth in the field. We studied four representative barley varieties grown in Tunisia under standard cultural practices for a semi-arid agricultural production region and monitored climatic conditions over three growing seasons. We found that autotoxicity of barley varieties increased under water stress regardless whether the source of autotoxic activity was roots, stems, or leaves of the barley plant. Results of this study are important to extension personnel and producers in semi-arid regions because they show that management decisions for barley production should include variety selection based on not only potential autotoxic effects of the previous barley crop but also on tolerance to drought stress during the growing season.
Technical Abstract: Barley (Hordeum vulgare L.) is widely cultivated in the semi-arid region of Tunisia for grain production and grazing, which often occurs during the same season. Barley growth is not only affected by prolonged drought but also by potential allelopathy from previous barley crops, known as autotoxicity, which we demonstrated previously. The present study was conducted to test effects of barley variety and seasonal variation on expression of autotoxicity by barley. Four barley varieties were grown in a field experiment over three growing seasons (1999-2000, 2000-2001, 2001-2002). Germination and seedling growth bioassays were used to assess autotoxicity potential of field-harvested barley in the laboratory. Barley autotoxicity was fully expressed based on inhibition of radicle growth detected in seedling bioassays. Stems were often the most allelopathic plant component. Allelopathic activity of the barley varieties differed across growing seasons suggesting the influence of a seasonal effect due to the extent of water deficit during the dry season and monthly rainfall variability. Results suggest that when planning to integrate barley within cropping sequences, barley producers should carefully select appropriate barley varieties to minimize autotoxicity, which can be more severe under drought conditions.