When Geoffrey von Maltzahn was first pitching farmers to try out his startup’s special seeds, he sometimes told them, half-acknowledging his own hyperbole, that “if we’re right, you shouldn’t just see results in the field, you should be able to see them from outer space.” As the co-founder of a company called Indigo Ag, von Maltzahn was hawking a probiotic that he hoped would increase their crop yields dramatically.