Evaluation of the Effect of SoyaSignal Technology on Soybean Yield [<i>Glycine max</i> (L.) Merr.] under Field Conditions Over 6 Years in Eastern Canada and the Northern United States

Abstract

Previous studies showed that inoculation of soybean [ Glycine max (L.) Merr] with Bradyrhizobium japonicum preactivated with plant‐to‐bacteria signal molecules increased nodule number, particularly at low root zone temperatures, thereby improving plant seasonal nitrogen fixation and final grain and protein yield under cool spring conditions. Two products carrying this technology, SoyaSignal TM and Affix+ TM , were designed and tested at 127 locations in Canada and the United States from 1994 to 1999. A summary of the field test results shows that preincubation of B. japonicum with genistein and daidzein, as well as directly increasing the genistein and daidzein concentration in the soybean root rhizosphere, gave an average final grain yield increase of 7 %. The success of SoyaSignal technology was temperature dependent. The plants responded better to the SoyaSignal products when grown under cool soil conditions. Application of SoyaSignal to early planted soybean (before the soil temperature rose above 17.5 °C) increased yields by an average of 10 %. The responses declined with delayed planting dates. Soybean genotypes with high yield potential had greater yield increases than those with low yield potential. As the ratio of return to cost for SoyaSignal technology was 5.3 : 1 over the 127 site‐years, SoyaSignal technology can be used as a tool to improve soybean yield in production areas with cool springs.