Maximum Yield USA May 2018 | Page 77

One example of biomimicry in action is found in the northern Sonoran Desert countryside surrounding Tucson, Arizona. Here, agricultural ecologist Dr. Greg Barron-Gafford and farmer, research scientist, and MacArthur Fellow Dr. Gary Nabhan combine concepts from Mother Nature with agrivoltaics, a system in which a single piece of land is used for both solar photovoltaic power production and conventional agriculture. More specifically, they took lessons learned from nurse plant ecology and applied them to reduce water use and carbon footprints in food production. In their plots at Biosphere 2, the world’s largest living research center, and at Manzo Elementary School, which was awarded Best Green School 2012 by the US Green Building Council’s Center for Green Schools, Nabhan and Barron-Gafford are experimenting with using solar panels as “host plants” and growing crops underneath them. “Solar panels create a little heat island effect and, as they warm up, they become less effective to the tune of about half a per cent efficiency loss for every one degree Centigrade increase,” Barron-Gafford explains. “Traditionally, panel installers have gotten rid of under- vegetation before construction. But, plants take carbon out of the air and in the process, moisture escapes and that transpiration, like human perspiration, creates localized cooling. We theorized if we stuck some plants under the panels, the in-ground and the above-ground efforts would both benefit.” “We took biomimicry and applied it to food production,” Nabhan says. “Controlled environment settings (ergo, greenhouses) help, but semi- controlled, climate-buffered shared environments adapted from 4,000 years of field agriculture using what’s available—urban heat islands that allow us to grow food under elevated solar panels acting as nurse plants integrated into an agrivoltaic agro-ecosystem—work well too.” “ When we look at what is truly sustainable, As they’re in the southwest US, the researchers started with salsa gardens, growing jalapeños, tomatoes, and the only real model that has worked over chiltepin peppers, both under the panels and in open long periods of time is found in the plots for four months. The contrast was astounding and led to further trials with chard, cabbage, carrots, basil, and even some mango and avocado trees. After their first year of experiments, the findings are promising. “Plants under the panels receive less direct sunlight, which leads to reduced evaporative loss of soil mois- ture that allows for significant water savings,” says Barron-Gafford. “Even if you irrigate every day, there’s still some savings. An agrivoltaic system keeps things about four per cent wetter. You have to water every day in an open system, but only every fourth day under cover.” He also notes the microclimate under the panels “is cooler because of the moisture release.” In open fields where summertime temperatures soar into the triple digits for weeks on end, this is a boon to both crops and the skin of workers. “One of the things we’re excited about in our agrivoltaic gardens is they allow us to really push the seasons. The planting calendar is not the same anymore; it’s now a blended calendar,” says Moses Thompson at Manzo Elementary School. “There’s so much flexibility. It’s all unknown and exciting. We could be running all warm-season crops under cover during the winter and they would be fine. I’m curious to see how long we can push the cool- season stuff as the warmer weather arrives.” natural world.” grow cycle 77