Darwinian Agriculture blog

Alfons Balmann has reviewed my book in the Journal of Bioeconomics.

"As opposed to the somewhat ideological arguments frequently raised by the proponents of these approaches in public debates on topics like GMOs and organic farming, Denison's concerns are not motivated by a wholesale rejection of these approaches, but by a substantiated assessment of their limitations, and by developing alternatives."

First, though, I'll be speaking at Evolution 2013, in Snowbird, Utah. I was also planning to speak at the Intecol (Ecology) meetings in London -- until I saw their outrageous registration fee, with no single-day option. I'll be at the the much-cheaper Ecology meetings in the US, though, right across the river in Minneapolis.

"We like to buy local food... despite the fact that the increased transportation costs of locally grown food make for a greater carbon footprint..." -- Comment from John Gorentz on blog Front Porch Republic

It's hard to argue with someone who says my book is "quite a page turner" but I think he may be over-stating his case a bit, to emphasize the point that buying local food doesn't necessarily save energy. I do the same thing on the last page of the book.

Near the beginning of the question period for this recent lecture at the University of Minnesota, I suggested that:

1) nobody has done a good comparison of ideotype breeding with breeding for yield, and
2) many plant breeders who use the word "ideotype" ignore tradeoffs.

The main point of Donald's 1968 paper, which coined the term, "ideotype" was that there are often tradeoffs between individual-plant competitiveness and the collective performance of plant communities, so we can improve the latter by sacrificing the former. That's a major theme of my book, as well.

But both my numbered points above turn out to be wrong, at least partly.

Yuan et al. (2011) compared ideotype breeding with breeding for yield. I criticized some of their choices for "ideotype traits" in my third lecture at the International Rice Research Institute, but it's still an impressive study.

And, rereading Rasmusson's 1984 paper on ideotype breeding, I find extensive discussion of tradeoffs, though he doesn't explicitly mention the tradeoff between competitiveness and yield potential hypothesized by Donald (1968).

I am correcting these errors in an perspective I'm writing for the journal, Evolution.

...or whatever we call over 100 but fewer than 1000 views.

This page has links to an interview Michael Joyce did with me at the end of my week-long visit to the International Rice Research Institute, as well as the five lectures I gave there (plus audience questions and discussion).

Also still available are:
* a 60-second AAAS story on my most-cited paper.
* a video of my keynote talk at the Applied Evolution Summit
* a lower-quality video of a talk on Evolutionary Tradeoffs as Agricultural Opportunities
* an audio interview with science writer Carl Zimmer

Or, you can find an updated list of my publications, with links to many of them, here.

"Crops that take up nutrients faster may reduce some wasteful nutrient losses (for example, leaching [see glossary] of nutrients in water percolating down through the soil), but every atom of nitrogen or phosphorus that is sold off-farm in grain, milk, or other farm products still needs to be replaced, for long-term sustainability... " -- Darwinian Agriculture, p. 67

This conservation-of-matter argument was the basis of my argument, in my fifth lecture at the International Rice Research Institute (IRRI), that rice with improved phosphorus uptake might offer mostly short-term benefits. (A slide with the only field data I've seen on this rice mysteriously disappeared, about 14 minutes into the talk.)

But the abiotic-stress group at IRRI called my attention to another approach to "the phosphorus problem" that seems really promising. Actually, there are several phosphorus problems:
* Phosphorus fertilizer is expensive, and it will get more expensive as high-phosphorus ore reserves are depleted.
* Some soils bind phosphorus, limiting its availability to plants.
* Phosphorus, mostly from livestock manure, is a major contributor to water pollution.

In the book, I mention crops with "proteoid" roots or increased symbiosis with mycorrhizal fungi as possible ways to increase crop uptake of less-available forms of phosphorus. But that doesn't solve the conservation-of-matter problem, i.e., the need to replace phosphorus in grain sent to distant cities or feedlots. The eventual depletion of phosphorus reserves seems such a severe (though perhaps distant) problem, that I briefly mention the "back to the land" option, to facilitate recycling of phosphorus in our waste.

But what if 1000 kg of grain contained only 1 kg of phosphorus, instead of 4 kg? We could then reduce phosphorus fertilization by 75%, making phosphorus reserves last four times as long. (OK, this isn't a permanent solution, but it could give us many more decades to find a permanent solution.) I didn't consider this option in the book, because I assumed that low-phosphorus grain would be less nutritious.

The abiotic-stress group at IRRI corrected my misinformation. It turns out that much of the phosphorus in grain is in the form of phytate, which neither we nor our animals can digest. So it ends up in manure. I'd heard about attempts to reduce phytate levels in seeds as a partial solution to the phosphorus-pollution problem. But low-phytate seeds would also reduce amount of phosphorus exported from a farm in each ton of grain, which would reduce the need for phosphorus inputs to replace it.

This seems like a win-win solution. Why didn't natural selection think of this? The phytate isn't there for our benefit; it's there to supply the phosphorus needs of the germinating seed and seedling, until it can grow enough roots to get phosphorus from the soil. We might therefore expect low-phosphorus seeds to grow poorly, although this isn't necessarily true for high-phosphorus seeds that have less of their phosphorus as phytate.

Low-phytate seeds with high total phosphorus would be more digestible, increasing the fraction of their phosphorus that ends up in meat or milk rather than manure. So they could reduce pollution. They wouldn't reduce the need for phosphorus inputs, however.

But what if we could supply the phosphorus needs of growing seedlings externally? If 99% of seeds get eaten, and only 1% get planted, could we give the 1% some extra phosphorus, perhaps as a seed coating? I don't see any fundamental (e.g., conservation-of-matter) reason why this wouldn't work, though it would probably require a clever combination of plant breeding and agronomy.

All five of my Darwinian Agriculture lectures at the International Rice Research Institute are now available on YouTube. My talks were prepared in advance, so I was only able to incorporate a small fraction of the interesting things I learned during my visit.

My last talk discussed the tendency (not necessarily by scientists themselves) to exaggerate research progress. For example:

"The researchers have already... successfully introduced 10 out of the 13 genes needed for C4 rice." -- Rice Today, January-March 2013, p. 5

Wheat, rice, soybean and tomato use C3 photosynthesis, named for the number of carbon atoms in the first product of photosynthesis. Maize ("corn" in the US) and sugar-cane use C4 photosynthesis. In hot climates, C4 photosynthesis can support higher rates of crop growth, using less water.

My book (p. 62) uses C4 photosynthesis as an example of "something that may have been easy for natural selection (given millions of years) [but] extremely difficult for humans." So I was surprised to learn, before arriving at IRRI, that C4 photosynthesis only needs 13 genes and that they have already transferred 10 of them. Maybe "skeptical" would be a better word.

I should have asked about this when I met with Paul Quick, who is leading the C4 rice project at IRRI. I'm guessing that he told the magazine that they've identified 13 key genes so far, and transferred 10 of them. My impression, from our discussions, is that they don't yet know the total number of genes they will need to transfer.

They have a lot of smart people, at IRRI and around the world, collaborating on C4 research. C4 rice will need :

* Some way to pump CO2 into bundle sheath cells around the leaf veins, from adjacent mesophyll cells.

* A diffusion barrier around the bundle sheath cells to keep the CO2 from leaking out again.

* More photosynthetic chloroplasts in the bundle sheath cells than rice has now.

* Ideally, closer vein spacing. The assumption is that CO2 can't be pumped very far, so if veins are widely spaced, only a fraction of the leaf will have C4 photosynthesis. But Paul Quick told me that corn husks have C4 photosynthesis throughout the leaf, despite widely-spaced veins. Interesting.

They seem to have made considerable progress on most of the above. I don't think he mentioned any progress on the diffusion barrier, though, which seems more critical than vein spacing, at least to me.

One of the clever approaches they are using is to knock out genes in a C4 plant, at random, to see which of them are essential to C4 photosynthesis. How do they tell if they've knocked out C4? Because of their CO2-concentrating mechanism, C4 plants can survive at much lower CO2 concentrations than C3 plants can. So they grow the random-knockout plant population at 15 ppm CO2 -- the atmosphere is 390 ppm and rising -- and look for plants that don't grow. Sounds like cruelty to plants, but they rescue them before they die, by transferring them to a high-CO2 tent. They're also drawing on IRRI's huge (100,000 genotype) collection of rice varieties and rice's wild relatives.

I don't know if they'll succeed, but this seems like a reasonable test of our current ability to improve complex traits in crops. At a minimum, they should get a lot of useful information about photosynthesis, leaf structure, the evolution of complex traits, etc. This information could have applications beyond improving photosynthesis. For example, the ability to develop crops with wider or narrower vein spacing would have applications in developing more-digestible crop leaves (for cows or for biofuel production). Vein spacing may also affect drought tolerance. Whether spending the same amount of money on other kinds of agricultural research would make more sense is a more-complex question. But the Gates Foundation is funding this "high-risk, high-potential-reward" research, so it doesn't come at the expense of their other work.

For more information, see IRRI's C4 rice page. For an interesting history of the project, see this video interview with John Sheehy, former head of the C4 rice project, who back visiting IRRI the same week I was there talking about Darwinian Agriculture.

My talks at the International Rice Research Institute are have been posted on Youtube and have already "gone reptile" or whatever you call it when a few people watch them.

I've been enjoying my meetings with staff here. Some highlights so far:

Paul Hilario, curator of the IRRI museum, told me about the "community rat-barrier" strategy for reducing rat damage to rice. A small plot of rice is surrounded with a fence with a few holes. Rats are attracted to the plot and crawl in through the holes, each ending in a trap, so most of them are killed before they can reproduce. Sort of a black hole for rats. But it only works if the "trap plot" is more attractive to rats than other rice nearby. So coordination among farmers (planting nearby rice later than the trap plot) is key.

Next I met with Ruaraidh Sackville Hamilton, who's responsible for IRRI's 100,000-genotype rice collection. Here's a great story about that. He mentioned another example of cooperation among farmers being key to disease control. If every farmer in a region plants the same barley variety, that increases the risk of disease epidemics. So farmers in the UK coordinated choices to ensure high levels of diversity, at a regional scale. I don't know if this works better than if each farm had high levels of diversity, but it's probably better than if one farmer had high diversity and her neighbors didn't.

John Sheehy's seminar was another highlight of my first day at IRRI. He initiated a program to develop rice with the efficient C4 photosynthetic pathway, with funding from the Gates Foundation. That work is being continued by Paul Quick. They're using some very clever approaches, which I'll discuss in a later post, but success isn't certain and it will certainly take a while. So, Sheehy asked, what else can we do to increase the yield potential of rice?

Sheehy presented a bunch of simple equations: photosynthesis equals solar radiation times the fraction of that radiation intercepted by green leaves, times a radiation-use efficiency term, and so on. This overall approach is similar to what I used to teach in my Crop Ecology class at UC Davis, which I inherited from Robert Loomis. (Sheehy and I each taught the class as sabbatical replacements for Loomis, years ago, and we've both published on the physiology of legume root nodules.)

Sheehy pointed out that maximum yield occurs at the point when net growth is zero, that is, when biomass gets large enough that maintenance respiration balances photosynthesis. Maintenance respiration increases with temperature, so maximum yield will be less in warmer climates. This explains some yield differences that had previously been attributed to better cultivars or better management. I suspect that maximum production per day occurs much earlier than maximum yield, so it may make sense to harvest and plant another crop rather than waiting. Hoping to discuss this with Sheehy.

He also pointed out that leaves aren't important only for photosynthesis, but also as a place to store nitrogen which eventually gets used for grain nitrogen. You don't want the leaves so close together that they shade each other, so there are limits to how short rice plants should be, even though investing resources in stems rather than grain seems wasteful.

It's not a book tour, exactly, but an increase in speaking invitations from my usual 1-3 per year.

22-27 March 2013. Darwinian Agriculture. A five-part series of lectures and discussions at the International Rice Research Institute, Los Banos, The Philippines.

4 June 2013. Evolutionary tradeoffs as constraints and opportunities. LANGEBIO, Irapuato, Mexico.

23 June 2013. Darwinian Agriculture. Evolution 2013. Snowbird, USA.

4-9 August 2013. Darwinian Agriculture. Annual Meeting, Ecological Society of America, Minneapolis, USA.

18-23 August 2013. Evolving More Beneficial Crop Symbionts. INTECOL 2013. Joint meeting of the International Association for Ecology and British Association of Ecology. London, England.
Part of a symposium on "Applying Ecological and Evolutionary Knowledge to Increase Agricultural Yield and Sustainability", organized by Jacob Weiner.

I will also be attending the North American Congress on Symbiotic Nitrogen Fixation, here in Minneapolis, and a workshop on Evolutionary Origins of Multicellularity, in Durham, North Carolina.

Glyphosate-resistant Giant Ragweed Over-topping Roundup-Ready Corn. Photo by Dr. Bill Johnson.
Source: International Survey of Herbicide-Resistant Weeds.

The same website has a list of herbicides, ranked by the number of weeds that have evolved resistance to them.

From p. 4 of Darwinian Agriculture:

"Widespread use of transgenic crops resistant to the weed-killing herbicide (see glossary) glyphosate presumably increases the use of that herbicide, while reducing the use of other, more-dangerous herbicides, at least until weeds evolve resistance to glyphosate."

Do organic farming rules sometimes undermine sustainability? See this blog post by Andy McGuire, who earned an MS with me (for his research on legume cover crops) in 1996. Some of the comments are worth reading as well. The one by "RachelL" raises some of the same issues as the last chapter of my book.