Investigating the role of soil legacies on root volatile emissions and belowground herbivory in maize

Despite the increasing importance of studying belowground interactions for plant health and food security, much of what happens underground remains a mystery. As researchers and farmers find new ways to grow crops while also mitigating environmental damage, understanding how these different agricultural practices affect belowground interactions is crucial. Cover cropping is one agricultural practice that has gained traction for its proven benefits in soil fertility and water retention. However, less is known about how cover crop soil legacies affect belowground interactions in subsequent cash crops. We grew corn (Zea mays) in soil collected from three different winter-grown cover crop monocultures, Austrian winter pea (Pisum sativum L.), forage radish (Raphanus sativus L.), and triticale (xTriticosecale), as well as a cover crop mixture and in soil that had been left fallow. After five weeks, plants were infested with western corn rootworm (WCR, Diabrotica virgifera virgifera). Corn plants grown in pea cover crop soil were significantly larger than plants grown in other soil treatments, and WCR larvae recovered from corn plants grown in fallow soil had gained significantly less weight and were less developed than larvae recovered from other plants. We detected significantly more belowground volatile compounds from treatments containing larvae than those without, and we were able to predict the presence or absence of WCR in a machine learning algorithm that had over 70% accuracy. Results indicate that cover crops can leave a soil legacy which significantly impacts belowground volatile emissions and root herbivore fitness.