Allelopathic potential of sorghum, wheat and maize residue extracts on germination and early establishment of Amaranthus hybridus L. and Rottboellia cochinchinensis L.

Allelopathy is an unexploited phenomenon in Zimbabwe which has the potential for use in weed management. There is need for a paradigm shift towards ecologically sound and affordable weed management methods. This study investigated the allelopathic effects of maize, sorghum and wheat extracts on germination and early establishment of Amaranthus hybridus and Rottboellia cochinchinensis. The bioassay had 50 and 100% concentration of sorghum, maize and wheat residue extracts. The results indicated that 50% sorghum resulted in the lowest germination (P<0.05) for A. hybridus and for R cochinchinensis (P<0.05). Wheat at 100% resulted the highest germination for both shamva grass and pigweed. Leaf lengths were not affected by residue extracts. A hybridus dry matter was not affected by type and rate of extracts. R cochinchinensis however showed a significantly lower dry matter at 100% sorghum residue extracts and at 50% wheat residue extracts. Wheat and sorghum resulted in significant weed suppression compared to maize and pure water. The sorghum and wheat mulches can therefore be used in suppressing the germination and early establishment of the two weeds.