GROWTH PROMOTION OF MAIZE BY SOYBEAN ROOT EXUDATES

Soybean [Glycine max (L.) Merrill] rotation with maize (Zea mays L.) can increase maize yield, but its mechanism has not been fully understood. The effects of soybean root exudates at trefoil stage (prior to nitrogen fixation ability) on maize seedling growth were studied under laboratory and field conditions in this study. Results showed that soybean root exudates at trefoil stage clearly promoted maize growth. Further HPLC analysis showed that soybean root exudates contained substances that promote plant growth, such as triacontanol. Maize growth exhibited significant differences when soybean root exudates were applied at different concentrations. Altogether this indicated that allelopathy, in addition to an increase in soil nitrogen, was an important mechanism of soybean promotion of maize yield during crop rotation.