Recently in Scaling up Category

That's the topic of a thoughtful essay by Nathanael Johnson on the Grist website. He gives a reasonable summary of my argument that many hoped-for improvements either involve tradeoffs (some of them acceptable) or radical enough changes that their effects will be hard to predict.

He also cites my colleague Jonathan Foley's suggestion that "we" should "Reduce food waste, eat less meat, and make fertilizer and irrigation available to the farmers that need it."

OK, but who's "we"? Any "solution" that requires billions of people to change what they're doing -- because they read Foley's article in Science? -- will be a long time coming. For example, a few million rich consumers eating less meat -- this would lower the demand for meat so that meat prices decrease so that slightly-less-rich consumers eat more meat, but let's pretend total meat consumption goes down a few percent -- would not have much effect on global greenhouse gas production or food security for the billion or two in greatest need. Similarly, if a couple billion consumers wasted less food, that would free up some resources. But if you and a few friends reduce your waste, it's a drop in the ocean.

Reducing pre-consumer food waste has more potential. Because reducing pre-consumer waste could mean larger profits for farmers, food companies, etc., near-universal adoption of practical waste-reducing methods is at least conceivable. Motivation linked to higher profits also means, however, that the obvious improvements have already been made. Less-obvious improvements are already a major research focus, but more likely to be invented by engineers than ecologists.

Expanding access to irrigation might greatly increase food security, but it would be a big project, perhaps costing a significant fraction of what we spend on war or video games. So I'm not holding my breath.

Increasing access to fertilizer can start small and scale up -- avoiding over-fertilization -- so that's an area where contributions from a few million people (or a handful of rich people) could really make a difference. But I worry about solutions that require on-going subsidies.

And then there's plant breeding. Develop a cultivar that out-performs what's available now, and watch it spread.

There's an interesting discussion of this issue at Biology Fortified blog. The post is by my first MS student, Andy McGuire, who also has interesting things to say on a blog from Washington State University, where he works.

Andy's post was apparently inspired partly by something I wrote last year, showing my estimates of how much nitrogen flows from synthetic fertilizer to conventional corn to chicken manure to organic farms.

I don't get too excited about whether organic farmers should be allowed to use manure from conventional farms, or whether we should "blame" them for the fertilizer used to grow the corn to feed the chickens. My point was simply that this dependence limits the potential for expanding organic agriculture. (So advocates of organic farming should be showering me with money for research on nitrogen-fixing legume crops and forages -- but that's another story.)

More interesting is this open-access paper, titled "To what extent does organic farming rely
on nutrient inflows from conventional farming?
" The paper has some actual numbers on nutrient fluxes to organic farms from conventional ones in France. While my earlier diagram assumed that an organic farm relied entirely on manure whose nitrogen originally came from synthetic fertilizer, the French study estimated that only 23% of nitrogen (though 73% of phosphorus) supply to organic farms came from conventional sources. But let's look at some details.

First, there are apparently some differences from US practices:

"European regulations recommend to use organically produced animal manure but allow the use of conventionally produced manure, provided that it is not the output of 'factory farming'."

I don't think we have that restriction in the US. Second, they found that:

"More than 80% of nutrient inflows through manures (82%, 85% and 81% for N, P and K, respectively)... came from conventional farming"

So 82% of N in manure came from conventional farms, but that was only 23% of estimated total N supply. The rest (almost 60% of total N inputs) was mostly estimated to come from biological nitrogen fixation:

"N fixation was estimated using the model proposed by Høgh-Jensen et al (2004)... based on the total N amount in leguminous crop biomass, multiplied by the ratio between the amount of symbiotically fixed N and the total N amount in the crop biomass."

That seems to be about all they said about biological nitrogen fixation -- I would have liked a little more detail. They also say that unsustainable "soil nutrient mining" (failure to replace nutrients exported in crops or otherwise lost from soil) was "not considered." A simple approach to that problem would have been to estimate nitrogen and phosphorus contents of products sold off-farm, and compared that to total inputs. If inputs exceed outputs, some of the difference may end up polluting groundwater, although some may be accumulating in soil, at least for a while. If outputs exceed inputs (including biological nitrogen fixation), over the long term, they will not be able to continue farming over the long term.

My conclusion is that organic farms that rely on manure from other farms (or on manure from their own animals, which are fed grain or hay from other farms) are dependent on conventional farms and therefore not a model that can be scaled up. That doesn't mean they are not making a positive contribution, if they are using manure that would otherwise end up polluting rivers.

If we can believe the nitrogen-fixation estimates in this paper, French farms are already getting a majority of their nitrogen from symbiotic rhizobia in the root nodules of their legume crops and forages. Maybe that could be scaled up. But if 75% of their phosphorus is coming from manure from conventional farms anyway, there may be little point in trying to replace the nitrogen in that manure with biological nitrogen fixation.

Scaling up?

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The online magazine Next City quotes me in an informative story about urban farming.

Dunn admits there aren't enough high-end restaurants or CSA customers willing to pay a premium for the produce generated by 10 or 20 one-acre [urban] farms, much less 10,000. He's looking for alternative buyers, such as hospitals or schools, but has yet to hit on a scalable option.

So-called "vertical farms" have additional problems, but I run into this scaling problem all the time.

When I was at UC Davis, people gushed about how much "more sustainable" a farm that grew seeds of native plants was, relative to those growing wheat, almonds, or tomatoes. Great, but that one farm pretty much saturated the market for native-plant seeds.

My brother earns a reasonable income growing wonderful vegetables and fruits organically, but that doesn't mean it would be easy to convert all our farms to organic methods. If each acre of organic farm needs manure from chickens fed corn from four acres of land fertilized with synthetic fertilizer, that seems to set an upper limit of 25% for organic farmland. Long before that, though, we might run out of customers willing to pay organic premium prices.
OrganicFarmManureSource.jpg