The University of Minnesota is ending this blog platform. I haven't decided whether to continue somewhere else.
Bob Loomis died March 27 and will be honored at a memorial service May 30, in Davis. I'll be there. An obituary published in the Sacramento Bee is available here.
He may be best known for his book, Crop Ecology, a great resource for anyone interested in "evidence-based agriculture."
He was indirectly responsible for my book on Darwinian Agriculture, in that he introduced me to many key ideas and classic papers.
Like my major professor, Tom Sinclair, he always seemed to put my interests ahead of his own.
This article by reporter Alison Healy is one of the better summaries of my ideas, including the famine-food hypothesis, which mostly disappeared from my book during editing.
Matt Dempsey covered my Dublin lecture in the Irish Farmers' Journal, but it's paywalled. Good article, except for confusion between rhizobia and rhizomes.
That's the title of my latest paper, now online at Field Crops Research. It will eventually be part of a special issue on yield potential.
There's some overlap with my previous publications arguing that many of the "improvements" proposed by biotechnology folks would duplicate traits that have arisen repeatedly in the past and have been repeatedly "rejected by natural selection" due to various tradeoffs. That doesn't necessarily mean those traits can't be useful in today's agriculture.
New material includes an assessment of the extent to which traditional breeding or biotechnology have improved tolerance to cold, flooding, or drought. Although crops probably pollinate their wild relatives more often than the other way around (because crops are more abundant), genes for stress tolerance mostly seem to move in the other direction. For example, high-altitude maize in Mexico has gained cold tolerance from teosinte, not the other way around. This and similar results suggest that natural selection is often better at solving tough problems than humans are. There are still plenty of opportunities for improvement through plant breeding or biotechnology, though. We just need to identify cases where past natural selection has worked against our current interests, and reverse the process. Shorter wheat and rice, less-bitter cucumbers, and thornless berries are a few examples.
Thanks to Billy Kingery for calling my attention to a recent paper by Chris Smaje, titled "The Strong Perennial Vision: A Critical Review", published in Agroecology and Sustainable Food Systems. The same journal published responses by Steve Gliessman and by Timothy Crews et al., to which Chris has responded on his blog, Small Farm Future.
These authors have probably thought about these issues more deeply than I have. And I don't want to try the patience of a couple of coauthors who are waiting for revisions on papers. So, for now, I'll just make a few comments on Chris's paper.
Among his points are 1) "there is no reason to suppose that lower-yielding perennial cereal crops cannot play a significant role in the sustainable food systems of the future" but 2) it's unrealistic to expect that they won't be lower-yielding. I tend to agree with both points. In my book, arguing for a diverse agricultural-research portfolio, I wrote:
"As explained in Chapter 7, I have my doubts about perennial grain crops. But do we really want to focus 100% of our grain-breeding efforts on annuals?"
One argument against claims that perennial grains will probably have lower yield is that apples sometimes allocate as much of their photosynthate to fruit as annual grains do to seed, as noted in a paper by Van Tassel et al. Chris points out that the apple trees in question were "physically supported and on strongly dwarfing rootstocks-- [and] are rarely grown commercially for [more than 10 years]." Chris's point is that this apple system isn't reliable evidence that perennial grasses could have high allocation to grain. I agree, but how much could we push the protein and calorie yield of tree crops? For example, could almonds be bred and managed to match the yields of annual grains? Even dwarf trees are taller than most weeds, so weed control could rely more on mowing and/or cover crops than erosion-promoting tillage or herbicides.
Chris notes that:
"some perennials (often C-strategists) can undoubtedly outperform some annuals in yearly resource capture, and this has been shown empirically in some cases, for example, in comparisons of Miscanthus with maize, alfalfa with soybeans, and perennial with annual sorghum (Piper and Kulakow 1994; DeHaan et al. 2005; Dohleman and Long 2009)"
but questions how much "breeders can manipulate plant allocation" to put extra resources acquired by perennials into seeds. He discusses this issue in some detail, but this still seems like an open question. Key to his arguments is Grimes' classification of plant strategies as competitive, stress-tolerating, or disturbance-adapted. If these strategies are really discrete and reflected throughout a plant's genome, I guess it would be hard to change. But given the apparent ease of transitions between annual and perennial (Silvertown and Dodd, 1966, cited by Smaje) or unicellularity to simple multicellularity, I suspect that it may not be too hard to change these strategies through plant breeding.
This wouldn't eliminate tradeoffs between individual-plant competitiveness and whole-crop yield, however. As Chris's paper states:
"It may indeed prove possible to select for high seed allocation in short-lived, C-strategy perennials whose growth habit enables them to accumulate more photosynthate than their annual counterparts, thereby simultaneously funding seed production and perennation. But, as Van Tassel (2012) concedes, these plants will be less competitive than co-extensive wild or weedy species--suggesting that the margin for cultivating them without resort to irrigation, tillage, fertilization, pesticide application and other such practices that perennial cereal cultivation aims to circumvent may be thin at best."
There's much more, including comments on sociological issues, so I expect this paper (and responses to it) will stimulate a lot of discussion.
My recent talk in Dublin, hosted by by the Irish agricultural-research agency, Teagasc, is now available on YouTube. Unfortunately, the photographer apparently thought video of me talking and the audience listening was more interesting than my data slides. Maybe it was a mistake to wear a tie. The Q&A session, where I respond to questions about organic farming and genetic engineering, didn't rely on slides, so might be more interesting.
Previous videos that show my slides well include:
* My 2013 department seminar at UC Davis.
Jeremy Cherfas recently interviewed me on Eat This Podcast, which has many interesting food- and agriculture-related interviews.
Earlier, Cherfas cofounded my favorite blog, the Agricultural Diversity Weblog, so I was delighted when he was the first to review my book. My book argues that crop rotation (with both crop diversity over time and lanscape-scale spatial diversity) often makes more sense than crop diversity within a field (intercropping). Jeremy's mostly-positive review points out that I neglected to discuss diversity within a species, such as growing a mixture of two or more wheat varieties. So I talk about that some in the podcast interview.
But in asking "how should we deploy crop diversity in space and time" both book and podcast implicitly assume that total usable diversity is limited. If there are currently only two wheat varieties that can be grown profitably in a given region, you have to choose between growing the same two-variety mixture every time you grow wheat, versus rotating (alternating) between them. (Growing them as a mixture further assumes they can be managed similarly, including planting and harvesting the same day, similar irrigation, etc. A rotation that alternates different wheat varieties could also include other crops or fallow years.)
If there are dozens of suitable wheat varieties, though, you could have lots of diversity both at different spatial scales and over time: different two-variety mixtures in different fields, without having to grow the same variety in the same field in successive years.
My main worry, though, is that world food security relies so heavily on just three crops (corn, wheat, and rice). In both the book and the podcast, I argue that farmers making rational decisions about their individual risks and benefits will collectively choose less crop diversity than we need to ensure global food security. I doubt that this example made it into Robert Frank's book (see last post), but the issues are analogous to those that caused the recent Great Recession.
That's the title of Robert Frank's latest book. Like my book, Darwinian Agriculture, it emphasizes cases where individual and group interests are in conflict. I suggest reversing past natural selection for traits that make individual crop plants more competitive, at the expense of whole-crop yield or water-use efficiency.
Similarly, Frank suggests that people make individually-rational choices that leave everyone worse off. For example, how much risk should an individual accept for a higher-paying job? Beyond a certain income, a higher salary mainly increases ones relative status. Buying a relatively more expensive house gets you into a neighborhood with better schools, but it doesn't increase the total number of kids who get to go to that school. So, more workplace injuries, but no overall improvement in education. He suggests progressive taxes on consumption rather than income.