Farmer knowledge, attitude and practices on sorghum allelopathy in five sorghum producing districts of Zimbabwe

Abstract

Lack of knowledge about allelopathy technology may be a barrier to the adoption of allelopathy by farmers. A questionnaire survey together with physical weed sampling in farmers’ fields were conducted to examine farmer knowledge, attitude and practices on sorghum allelopathy and to establish weed density in fields grown to sorghum (Sorghum bicolor (L.) Moench) during the 2015/2016 and 2016/2017 growing seasons in five districts of Zimbabwe. A third of the farmers (29%) knew about and associated poor weed growth with sorghum allelopathy. About half (49%) left sorghum stalks standing in plots after harvesting and later ploughed them under, while 6% cut and burnt them. Both previous and current season sorghum significantly (p < 0.05) affected density of Eleusine indica (L.) Gaertn., Bidens pilosa L., Acanthospermum hispidum DC and Richardia scabra L., suggesting that allelopathic effects of sorghum can be caused by both residual and freshly exuded allelochemicals. Five varieties suspected to be allelopathic by growers were evaluated for sorgoleone content. There were significant (p < 0.001) differences in sorgoleone production among the five varieties. The detection of very low levels of sorgoleone in some of the varieties suggest that compounds other than sorgoleone contributed to the suspected allelopathic effects.

Keywords:

• allelochemical
• persistence
• sorghum stover
• sorgoleone