Allelopathic effects of sorghum species on weed seed germination and dry matter accumulation in different soil types

Weeds are problematic and burdensome to many smallholder farmers in Zimbabwe. The continued existence of allelochemicals in plants inhibit weed seed germination, plant growth and nutrient uptake. A study was carried out to assess the effects of sorghum species on weed seed germination and dry matter accumulation in different soil types at Duncanstan Farm in Featherstone, Zimbabwe. A 3x3 factorial experiment was laid out in a completely randomized design (CRD) with nine treatment combinations replicated four times. Soil type was the first factor with sand, loam and clay soils. Sorghum plant extracts, Sorghum arundinacea and Sorghum halepense, formed the second factor, and the control had no extract. All soil types showed significant effects p<0.05 in the reduction of germinated weeds treated with S. arundinacea and S. halepense water extracts compared to the control. There was significant decrease p<0.05 in the mean fresh and dry matter accumulation of weed seedlings in both treatments of S. arundinacea and S. halepense water extracts in all soil types. In sand soil, the mean fresh weights were 33.4g and 36.3g in S. arundinacea and S. halepense respectively as compared to the control treatment with 58.2g. Similarly, the mean dry weights were 15.4g and 14.9g. In conclusion, Sorghum arundinacea and Sorghum halepense possess allelopathic effects which can be used for effective weed management. It is recommended that sorghum species be conserved and used as bio-herbicides and in the development of synthetic herbicides.