Relative Ability of Soybean, Fallow, and Triacontanol to Alleviate Yield Reductions Associated with Growing Corn Continously
Corn (Zea mays L.) usually yields more when rotated with soybean [Glycine max (L.) Merr.] than when grown continuously. The exact reason for this yield increase in unknown. One objective of this study was to determine whether the increase in rotated corn yield is due to a positive influence of the soybean or to the absence of a negative influence of continuous corn. An alternate year of fallow was compared to an alternate year of soybean to determine which was more effective in alleviating the yield reduction associated with continuous corn. A second objective was to determine if an application of triacontanol (no chemical name available) (TRIA, reported to be present in soybean residue, and to enhance the growth and yield of corn) might alleviate the yield reduction associated with growing corn continuously. Each treatment consisted of a 3-yr cropping sequence. Corn was the crop during the first and third years. During the second or alternate year, the plots were maintained in corn, soybean, or fallow. In one series maintained in corn, the crop was treated with TRIA during the seedling stage of the third year. Corn yielded significantly better and equally well when rotated with either soybean or fallow. TRIA had no effect on corn grain yields. It appears that improved grain yields when corn is rotated with soybean are not due to the presence of TRIA or any growth promoting influence left over from the soybean. Rather, the yield increase must be due to the absence of some negative effect that otherwise persists in the soil when corn is grown continuously.
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