Tech companies are raising hundreds of millions of US dollars, including backing from agriculture heavyweights such as Bayer AG, for developing farm products that use living things such as microbes and seaweed to nourish crops and lessen the need for synthetic fertilizer. Microbes, including fungi and viruses, have been available for decades as treatments to protect plants from insects and disease, with mixed results. However, developers are increasingly deploying them as natural ways to nurture crops, while maintaining crop production levels. Such products could help farmers lessen applicatio...