However, the wheat may be injured and its yield reduced by allelopathic effects of the sorghum. Injury might be decreased by planting varieties of wheat that are resistant to allelopathy, but none have been identified. Allelopathy also might be reduced by proper management of the sorghum residue. After the toxic compounds leach from the residue, they are degraded into harmless chemicals by microorganisms in the soil. Tillage of the residue undoubtedly affects leaching and degradation of the allelopathic compounds, but the most effective methods have not been determined.
Information is needed to help producers avoid the problem of allelopathy in wheat.
G, a hybrid that is highly allelopathic to wheat, was planted in two blocks at the North Agronomy Research Farm in Manhattan in early June of 1996 and 1997. The sorghum and pearl millet were grown as recommended, and the grain of both crops was harvested in early October. One of the sorghum blocks and the fallow block were tilled with two passes of a disc immediately after harvest. The other sorghum block and the pearl millet block were left untilled. Nitrogen fertilizer was applied as needed according to the soil analysis to equalize nutrients in all the blocks.