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.