“Straight up” beats “cocktails” for cover crop ecosystem services Cover crop mixtures, known as “cocktails” by some, are being promoted as having benefits over cover crops planted as monocultures. As I described in Part I, I reviewed recent research results to get at the answer to the question, “are monocultures or polycultures better when it comes to cover crops?” I found that, for biomass production at least, monocultures were actually best. Now, let’s look at other services provided by cover crops and compare polycultures and monocultures. (See an explanation of monocultures, polycultures, overyielding and transgressive overyielding in my post Ecological Theories, Meta-Analysis, and the Benefits of Monocultures.)
“Straight up” beats “cocktails” for cover crop productivity Planting cover crop mixtures is very popular right now. The practice has a feel-good aspect about it and, buoyed by the ecological theory, it fits with the current “mimic nature” strategy of agroecologists. In Mixing the Perfect Cover Crop Cocktail I demonstrated how difficult it is to do research on cover crop mixtures. Although difficult, there are intrepid researchers investigating this practice so I decided to see what they were finding. The results call into question the value of cover crop mixtures, as in many situations a monoculture cover crop would both produce more biomass and provide other desired services as well.
How do we go about increasing agricultural crop yields? As long as human populations are increasing, this is the primary challenge we face in agriculture. We must do this without threatening our ability to produce food in the future, and, if possible, without expansion of agricultural land (see graph below, from The Return of Nature; How Technology Liberates the Environment).
It said on the screen, “Bioregenerating Soil-Based Space Agriculture.” The title of the talk was “Beyond Intensification.” The speaker, a prominent researcher and prolific author, is someone who I thought would present clear thinking on how, in addition to intensification of current agriculture, we can go about producing enough food for the earth’s growing population. I glanced around to see if anyone else was astonished. Space farming, he said, was the next step after agricultural intensification with food coming from the Moon and Mars. “Has it come to that?” I thought. I am a fan of science fiction. Not a costumed, Trekkie-conference fan, but a fan. However, over the years, I have realized that the stories I enjoy most are mostly fiction; the science is often ignored. This is “soft” science fiction, the stuff of most Sci-Fi movies because there is a way to visit distant planets; think warp drives
On a brown, August-dry field in Eastern Washington, a farmer in a combine cuts a 24-foot swath across a field of wheat. The harvested grain then begins a journey, first to the storage bin, then to the local elevator, on rail to a flour mill, by truck to a bakery, by oven to bread, and by car to a home where it is eaten. This is good; our foremost mandate to agriculture is to produce food. However, with this successful export of food from farm fields to nearby and distant cities comes a problem: the nutrients in the bread, the nutrients that we need from food, and that plants need to grow, are now far from the field they came from. How do we replace them? High yields worsen the problem. A typical irrigated winter wheat field will yield 140 bushels per acre; about 5,600 loaves of bread. For a center