Last summer, our farm experienced the same extreme heat and drought that broiled most U.S. farmland. Our pastures went completely dormant, and neighboring corn fields got crunchy brown. As the drought went on, we noticed that our summer cocktail fields were staying green and growing! They didn’t look lush, but compared to other fields, they were a cool, green oasis. We started searching for an explanation and ran into online anecdotes about cover crop mixes’ strange and wonderful ability to resist drought. We were excited to see these other reports, but we wondered if anyone had any measured proof.
We found some very exciting proof in North Dakota farmer Gabe Brown’s presentation at the 2012 Quivira Coalition conference. This video of his presentation is so chock-full of interesting information that the segment on drought resistance, which starts around the 9:30 minute mark, is kinda easy to miss. But I think it’s revolutionary and deserves studying.
Experiment Comparing Cocktail to Monocultures
He partnered with his Soil Conservation District in 2006 to plant and measure the yield of six plants (oilseed radish, purple top turnip, pasja turnip, soybean, cowpea, lupin). Each species was planted alone in a monoculture right next to the others. Then, they combined all six into a cocktail mix and planted the mix nearby. That year was extremely dry, even compared to his normally arid climate. With an unusual “open winter” with no snow cover, the seeds got planted into dry soil in mid-May. During the growing period, the plants received just a little over one inch of rain. The soil conservation district measured the crop on July 31st.
Here is a picture of his turnip monoculture – obviously stricken by drought.
Here’s his cocktail mix. It’s green and clearly a MUCH better crop than the turnips growing alone.
But the real proof in the pudding is this clipped & weighed production chart. He more than tripled his dry matter forage yield in a drought by growing a mix. Unbelievable! The results are even more exciting because I believe Soil Conservation Districts use standard methodology for measuring production – which lends some necessary scientific credence.
But What’s Going On?
So far, I’ve heard people explain mixes’ drought resistance by: (1) deep rooting plants bringing up moisture for other plants and (2) mycorrhizae fungi networks supplying moisture to keep plants healthy and growing.
Who knows the real reason? I think cocktail mixes simply capitalize on how nature has evolved to work over billions of years – via competition and indirect cooperation among many winners and losers (diversity). Diverse plant mixes seem very resilient, but maybe plant mixes’ great performance under stress is the “normal” standard to which we should compare monoculture performance, not the other way around. Monocultures are odd, not diverse mixes.
As Gabe Brown says in the video, “Why do we grow monocultures?” How much more productive could U.S. pastures and cornfields have been if they were highly diverse? Or if the cornfields at least had a diverse winter cocktail growing before the corn was planted? For our farm anyway, we’ll be planting cocktail forage mixes for summer grazing. They appear to be dependable insurance against drought, and much more affordable than purchasing hay at high drought prices. Thanks for reading!