Transforming Agriculture, Perennially


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Interview With an Ecologist: Tim Crews, Director of Research and Lead Soil Ecologist

Tim Crews, Director of Research and Lead Scientist for Soil Ecology

What got you into this field of work?

I became interested in agriculture and horticulture in high school. I subscribed to the book of the month club from Rodale Press back in the ‘70s and got interested in organic gardening. Then Wendell Berry’s “The Unsettling of America” came out in ’77, and that genuinely had an impact on me thinking about agriculture and a broader view of how society relates to the land as opposed to the narrower, garden-scale focus of not using chemicals when you’re raising vegetables. Wendell Berry had a huge influence on me, as I chose to attend UC Santa Cruz, which had a farm and garden program. I did the 6-month apprenticeship there, and then agroecologist Steve Gliessman showed up and I started to pursue agroecology, which was just becoming a thing. For my senior project, I got very interested in how to sustain soil fertility without purchased or exogenous inputs, and I ended up going to Mexico and studying a very traditional farming system that had been around for more than a thousand years which hadn’t ever used fertilizer. That experience informed the rest of my life’s work. I went to graduate school and did my dissertation in parts of Mexico to further understand the soil ecology of how traditional farmers were able to sustain crop production over time without fertilizers.

I stopped by The Land Institute in 1981 after reading “New Roots for Agriculture” in the agroecology program at Santa Cruz. I came out here my sophomore or junior year and met Wes and toured what lab facilities they had. Then I worked at the Windstar Foundation in Snowmass, CO after undergrad, and the land education program there invited Wes to give a talk at a “Choices for the Future” symposium, and we all met with him and connected. After that, I was in grad school at Cornell with his daughter Laura Jackson. Wes came through a couple times and spoke when I was there. That was back when TLI was mainly education programs with mostly recently-graduated undergrads who were spending a year here in the internship program. Then I collaborated with researchers here between 2000 and 2010, going to most of the grad fellows workshops at Matfield Green, and undertaking two sabbatical years, one in Australia and one in the UK, focused on Natural Systems Agriculture. After our daughters went to college and Wes was nearing retirement, I reflected on how, in all my years teaching agroecology at Prescott College which involved traveling with students all over the West, I grew to feel like the innovations that were taking place to make agriculture sustainable were not sufficient, and I still think that. The Land Institute was the only place that was striving for a solution that matched the scale of the problem.


Can you talk about some of your specific areas of focus with soil ecology?

Much of the interest I have in soils revolves around how soil fertility develops and is maintained. I’ve looked at that question in natural non-human ecosystems, in modern agroecosystems, and in traditional farming.  Agroecology as a discipline tends to draw lessons from how nature functions and how people pulled off agriculture before you could buy inputs made available through fossil fuels and other tricks. Both of those tend to be very useful in providing ideas about how we can move forward. When you’re interested in soil fertility, you tend to be interested in the stories of both nitrogen and phosphorus – two key elements that plants need a lot of. You also tend to be interested in carbon, which is the basis for soil organic matter. Soil organic matter plays a role in maintaining soil fertility because it holds nitrogen and phosphorus as key components, but the matter itself also helps maintain a certain tilth (a texture) and aggregates (clods which are very important in letting air and water and roots enter the soil).

In my research career, I’ve spent a lot of time looking at nitrogen fixation by legumes and other organisms. Legumes host the bacteria that fix nitrogen in their roots. But there are also other bacteria not in legumes which fix nitrogen that can be important in both agriculture and natural systems. I spent a lot of time trying to understand what helps and what limits those nitrogen fixers, because in a solar agriculture, that is the main way that nitrogen enters the ecosystem as opposed to industrial agriculture where we’ve figured out how to use fossil fuels to get nitrogen out of the air and make it available to our crops. That activity, called the Haber-Bosch process, is the most energy expensive input into modern agriculture. People often think it is tractors, but it’s obtaining nitrogen.

Phosphorus is a whole different thing because it weathers from soils and rocks and is constrained by how much those minerals dissolve and release those nutrients. That’s the process by which all the other required elements are released: calcium, magnesium, manganese, boron, and all these elements are dissolved by weathering of minerals. Typically, plants in natural systems get all they need of these other elements while nitrogen and phosphorus tend to be the bottlenecks of nutrients that limit plant growth.


2019 intern Madeline DuBois from Northeastern University uses a tall auger to prepare to place soil moisture sensors at varying depths below the root zone of a post-harvest Kernza-alfalfa intercrop in a Land Institute research plot.

You talked about nitrogen fixation being a benefit of Kernza®-alfalfa intercropping – what are some of the other benefits of intercropping?

We don’t currently know how much it cuts down on pathogens because Kernza doesn’t tend to have a lot of pathogens right now. It may in the future, when there’s more being grown, but right now, the plant is a source of resistance genes. Conventional wheat breeders cross wheat with Kernza or intermediate wheatgrass to pull some of those excellent genes into wheat to help protect it. People don’t know that some little portion of most wheat is already Kernza or intermediate wheatgrass.

There’s not a tremendous amount of insect pressure either. But we don’t know – there could be soil pathogens, there could be nematodes in the soil, there could be any number of things that might affect Kernza later in its life span, in year 3 to 5 or longer. Having another species inserted in the cropping system has been shown by many researchers to have a strong effect on limiting the spread of pathogens but also potentially herbivorous pest insects. We’re interested in also adding silphium on the margins – not necessarily every other row, but maybe every 10th row or in some other configuration that will go deep to pull up water and nutrients, as well as provide habitat for pollinators and beneficial insects that might consume pest insects of the crop. There are more pest insects on alfalfa than Kernza, so diversifying the system further will be of interest to see what happens in that respect.

Another thing that we’re looking at right now is how alfalfa could help provide water to the Kernza in drought years. We saw evidence of this last summer. We’d gone through a serious drought and cut the alfalfa in early June. Lee noted that Kernza really took off after we cut the alfalfa, and it hadn’t rained yet. We figured it couldn’t just be nitrogen, because there were other plots of Kernza that had received urea fertilizer which weren’t responding. Then we started to think that maybe it could be this thing called hydraulic redistribution, where the root system of the alfalfa possibly distributes water like a system of pipes, moving water from areas of higher concentration to lower concentration. It’s been shown to happen conclusively in numerous ecosystems. It’s specific to plants that have big root systems, vessels that can conduct a lot of water, so you don’t tend to see it in fine-rooted species like Kernza. In fact, there’s some thinking that Kernza probably doesn’t take up a lot of water at great depth. If it’s stressing and about to die, it can probably obtain survival water from really deep and it will stay alive, but it seems likely that the size of the Kernza roots cannot conduct sufficient water from a meter or two down to provide what it wants in its water consumption. It gets it in the top 50 cm or so, half a meter predominantly. But if you have alfalfa that has roots that go down 10 or 20 feet, which is possible with alfalfa (and they’re big roots) – especially if you cut the alfalfa so it is no longer transpiring water itself – it has the pipe system in the ground that is not actively using water. If water is down there at three meters, it may go up through the roots into the soil where it’s dry and hydrate the soil. And the Kernza might be taking it up. We think that might be what happened last year.

So, this year we put in soil moisture sensors at three depths. Madeline DuBois, an intern from Northeastern University in Boston, is overseeing this as part of an Independent Study she’s doing here. Of course, this year it’s rained so much, and the soil has been near saturation most of the time, we haven’t seen anything that hints at hydraulic redistribution yet. So, it hasn’t worked out so far in terms of testing that hypothesis. But maybe the soil will dry out enough in fall that we’ll see some movement of water in the system. It’s still interesting to see what’s going on with soil water movement that deep. We have the sensors at 30 cm, a meter, and three meters, some in the Kernza with alfalfa and some in the Kernza without, so if hydraulic redistribution happens, we should be able to see water moving up in the intercrop compared to the single species stand.


Looking at wide hybridization efforts like we are doing with Johnson grass and perennial sorghum, how many weeds are potentially available to eat and use in the perennialization of food? Because weeds are so prolific, are there other weedy species we could use for breeding?

Pretty much all our annual crops are cousins of weeds. Most weeds are in the same families as crops; many are grasses or legumes. In the tomato family, the solanums, there’s a bunch of weeds. Bindweed is in the sweet potato family. If you selected hard on seed yield of these annual cousins, they probably would lose some of what makes them such aggressive weeds. That’s kind of what’s happening with the wide hybrid in sorghum and Johnson grass – the farmers worry about us creating an invasive crop species, but we’re actually taming Johnson grass and making it less aggressive by allocating a lot of its resources to seed. If you took a wild tomato weed like a chokecherry and selected on it heavily to have big tomatoes or even cherry tomatoes, it probably would not be as prolific of a weed because of the trade-off in resources.


Will our use of wide hybridization develop crops faster in the breeding cycles than rapid domestication because you should have more information on the parent crop and its pathogens?

It has the potential to be faster because you’re able to take advantage of an annual crop that’s been bred for hundreds to thousands of years and thus you can maintain many of those attributes in the wide-hybrid cross. That’s exactly what’s happened in the rice project and when you look at some of Shuwen Wang’s wheat. The challenge, of course, is having the genetics stabilize to where the crop is a viable perennial. I’m hopeful that some of the various discoveries that have been made recently in both perennial sorghum and the wheat here at TLI will help make these crops robust perennials.


Do you have any important recent discoveries you can talk about?

One of my strong interests is how much energy it takes to grow food; the energetics of agriculture are key, and I think underappreciated by most people working in sustainable agriculture. Agriculture was originally pursued to obtain more energy for people. We lay out a large solar collector on the landscape, called our crops, and we eat the solar energy they collect. But it takes energy to sow, tend, and harvest crops, and there must be more calories in the yield than you spent growing it, otherwise you would starve. Usually there was a considerable energy return on investment in agriculture before the fossil fuel bonanza, which I peg at roughly the advent of the steam engine. After the fossil fuel bonanza, you can spend 100 times more energy growing this head of lettuce or this grain crop than it gives you, and it doesn’t matter, because you don’t rely on that food to grow the next crop. You’re getting all these fossil fuel slaves at the filling station and it takes nothing compared to the energy they give you, compared to human energy. That explains much of why we’re doing what we’re doing and how we do it right now in organic and conventional agriculture. As we try to reduce our extreme fossil fuel dependence, we positively need to address this, and we need to come up with an agriculture that uses far less energy and has a far greater energy return on investment. The work we’re doing here at The Land Institute holds the greatest promise, because humans do not need to work as much to make the ecosystem function, because the ecosystem functions on its own. People don’t have to clear the land and re-sow crops every year. If you have legumes in there, nitrogen fertility is provided. In healthy stands of perennial crops, many weeds are suppressed. All of a sudden, the ecosystem is functioning on its own without nearly the amount of human intervention, which has been a ball and a chain for 10,000 years for our ancestors having to invest such a large percentage of our time and energy making life feasible for annual crops. A post-fossil fuel society is probably going to involve more human labor in agriculture—some people don’t agree with me, but if it does, there will be significant social justice implications of developing an agriculture with a much higher energy return on investment.

At TLI, I’m excited at how well Kernza and alfalfa get along. Even though that seems like such a basic thing, people were skeptical when I first suggested intercropping those two. I don’t think I was the first. Jerry Glover tried it, but he broadcast the two together, and alfalfa tended to lose out in the competition to Kernza when they’re just growing in a field. I put them in rows and started managing them that way. People said, “Alfalfa’s a big water hog, in this semi-arid environment it’s going to knock Kernza out. Or both will suffer.” Over the years the two actually grow better and better together! This intercrop provides an exciting example of what we have to look forward to in ecological intensification as we discover other combinations of species that thrive together.


2018 intern Anna Andersson from Lund University, Sweden, sows Kernza into strips that were undercut in the large alfalfa patch

As Director of Research I know you are integral to the education efforts: selecting interns, working with the new resident program, and making sure people are getting a good learning experience. Could you talk a bit about that process?
TLI was known for its intern program before it became a full-on research institute around 1998. That intern element went away for a while and got replaced by the graduate fellows program around 2000-2008 or so. Those were graduate students who would only come for one week a summer and go to Matfield Green – I was involved in that project.

When I first started working here, it was mainly hiring recently graduated high school kids, maybe first year of college, to work with very little actual involvement in learning about what we were doing. It was more of a summer job. They might have been interested in science or environmental science, but not specifically our work. Gradually, year after year, we started to invite older college students to apply from schools all around the country.  We are after students who really want to come work here and are very interested in what we are doing. We accept maybe a third to a fourth of the students that apply. We are fortunate to consistently attract outstanding students—super people. We’ve also started hiring a few high school students, or recent grads to be farm hands.  These kids focus hard on keeping weeds under control in breeding plots and maintaining equipment.

The internship program has become more developed pedagogically, and I think the addition of Ecosphere Studies and Aubrey has positively enhanced it even further. The residents’ program I don’t take credit for – it was David and Aubrey’s initiative to propose it and they got Ebony, Brandon, and ultimately myself on board. I hope we will be able to continue it – it is a more expensive program because it’s year-round. I think all the residents will go to grad school and their research programs will probably have something to do with our work. That’s a pretty amazing investment payoff, inspiring undergrads to carry it into their life’s work. I’d love to see it continue.

Meanwhile, I am working with Aubrey to initiate another graduate/post-doc fellows workshop to rekindle a slice of what happened in the summers at Matfield Green. We will organize a workshop for most of the students who either receive support from the Perennial Agriculture Project or are pursuing projects relevant to our work in the lab of a collaborator. We would like all these early career researchers to have conversations to get to know each other and appreciate what TLI is and does. I’ve been wanting to do this since the Perennial Agriculture Project was formed five years ago, and it’s finally going to happen for the first time at the end of October this year.


Could you speak a bit about our increasing global partnerships?

The breeding programs all have global research partners. There’s been a lot of interest and receptivity in Europe especially. Meso-America is the area I feel is least involved – from Mexico to the tip of Patagonia. There’s a colleague of Brandon’s in Mexico, Damien and Alejandra in Argentina work with David, and Uruguay connections, but we need more. A major point of the perennial ag meeting last spring at Lund University in Sweden was to bring an international perspective to this work. In an exercise at the end of the meeting where participants were asked to discuss what scaling up our efforts would be like globally, there was pretty much a consensus across multiple break-out groups that there should be an international network for perennial agriculture and that it should be formed with TLI as the hub.

We are ready for there to be a more formalized organizational network, and we could imagine there being a person who would direct it. That person would help potentially orchestrate funding that would go to that network, even at modest levels, to fund the graduate students and provide seed money for new projects. A PhD student in Nairobi or Lima could apply to do a project. Maybe that network would also be in place so if we did get significant funding, we would have an organizational structure in place that would help facilitate the funding of more substantial clusters and research groups. We heard the enthusiasm for an international network loud and clear at Lund, and we’re excited about it. I see the next big step as exploring what that would look like.


With the different global researchers working on our grains like Kernza and perennial wheat, are they breeding their own perennial regional crops as well?

Not enough. Rice in China is the big one.  Then there is pigeon pea, which is an already-perennial legume grown in Africa quite a bit, and it has been used in some of the work in Uganda with perennial sorghum. Anna Westerberg is working to breed barley independently. There’s a group in China focusing on buckwheat. But for the most part, no.

There are groups taking on new crops, but we would like to see more of this taking place. That links to our work with the Global Inventory Project, which seeks to identify wild, herbaceous perennial species that are strong candidates for pre-breeding and eventual use in perennial crop polycultures in temperate and tropical climates. If we had an international organization, we could link that to maybe a journal or some kind of publication that would come out of this to encourage and facilitate different groups to start on domesticating new perennials in different regions. I’m excited about that possibility and thrilled at how the number of research partners we interact with has exploded in recent years.


Do you have any specific 5-10 year goals that you would consider your focus?

My own personal goal would be to develop an intercrop system, a polyculture that is highly functional and something that is relatively easy for a farmer to adopt, that could maintain the fertility of a relatively high-yielding perennial grain system.  I am also looking forward to achieving greater insight into the carbon sequestration potential and potential reductions in nitrous oxide emissions in all our crops.  At this point most of the work focused on greenhouse gases by TLI and other groups has been centered on Kernza.  I am especially interested in helping to facilitate work on the environmental benefits of perennial rice, too.

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