Sorghum allelopathy under field conditions may be caused by a combination of allelochemicals

Abstract

A field experiment replicated over two seasons examined allelopathic effects of eleven sorghum accessions with known sorgoleone content on sorghum growth and yield, weed density and biomass at Panmure Experiment Station, in Shamva, Zimbabwe in the 2017/2018 summer and in late winter to summer in 2018. The trial was a 2 × 11 factorial in a randomized complete block design plus two control treatments replicated thrice. Factor A was weeding regime with two levels: clean weeding and no weeding. Factor B were 11 sorghum accessions. There was a significant sorghum accession × weeding regime interaction effect (p < 0.05) on sorghum head weight. Weeding significantly (p < 0.05) caused heavy Macia heads compared to no weeding. There was a weak negative relationship between sorgoleone content and head weight (r = −.28, p = 0.413), and between sorgoleone content and grain weight (r = −.31, p = 0.357) in winter. There was a highly significant sorghum presence × weeding regime interaction (p < 0.001) on A. conyzoides and R. scabra density in summer. There was no significant correlation (p > 0.05) between sorgoleone content and weed density and biomass, suggesting that sorgoleone may not instantly cause allelopathic effects on weeds upon its release from root hairs because it is strongly sorbed in soil, and inhibition of density and biomass might have been caused by other allelopathic compounds. Future research should trace uptake and translocation of allelopathic compounds to target sites of receiver plants, and demonstrate that subsequent damage symptoms are caused by the allelopathic compounds.

Keywords:

• Sorghum allelopathy
• sorghum presence
• weeding

Reviewing Editor:

• Manuel Tejada, Universidad de Sevilla, Spain

SUBJECTS:

• Agriculture & Environmental Sciences
• Plant & Animal Ecology
• Soil Sciences

Acknowledgements

The authors are thankful to staff and management at Panmure Experiment Station, including Mr Kiven Garutsa and Mr Dumisani Sibanda for providing resources and advice on the trials. The research was partially funded by the Govan Mbeki Research and Development Centre. The International Crops Research Institute for the Semi-Arid Tropics, based at Matopos Research Station, Bulawayo, Zimbabwe, provided the sorghum germplasm. Gloria Hoshiki, Naume Humbe and Zivanai Sigauke assisted with root excision of sorghum seedlings. Mr Cosmas Mutsimhu, Chief Analytical Chemist at the University of Zimbabwe’s School of Pharmacy, Pharmaceutical Laboratories assisted with all the HPLC-MS analysis in a seasoned manner.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data will be made available upon request.

Additional information

Notes on contributors

Handsen Tibugari

Handsen Tibugari is an Associate Professor of Crop Science, and Chairperson of the Department of Crop and Soil Sciences in the Faculty of Agricultural Sciences at Lupane State University in Zimbabwe. His research interests are in Integrated Weed Management.

Cornelius Chiduza

Cornelius Chiduza is a Professor of Agronomy and Head of Agronomy Department in the Faculty of Science and Agriculture at the University of Fort Hare in South Africa. His research interests include agronomy and conservation agriculture.