Lucretia Sherrod is a soil scientist at the USDA Agricultural Research Service. She has researched dryland agricultural systems for over 25 years.
The following interview has been edited for clarity and length.
Steve Rosenzweig: Your research is largely focused on how to move beyond wheat-fallow into more intensified and diversified crop rotations. What is the secret?
Lucretia Sherrod: No-till is what allowed to get cropping intensity going. When we till the soil, we're automatically having more surface area opened up to evaporation. We're losing water just by tilling. So, no-till, by not tilling and having a surface armor of residue, allowed us to add other crops to the rotation.
SR: What sort of impact do these intensified rotations have on the soil?
LS: When you are diversifying your cropping systems and you have more than just one type of residue base out there, you have a lot more biological diversity as well. It's definitely bumped up from your traditional wheat-fallow only. Microbes are the pump. It's the heart of the soil. We're always going to have respiration going on, and in a wheat-fallow system we get no inputs during that fallow, so we're taking deposits out of the bank, and not putting anything in.
SR: You’re talking about carbon inputs – like organic matter, right?
LS: That’s right.
SR: And why should farmers care about microbes?
LS: You have more bacteria and fungi that are able to stay and colonize the system and create aggregates, and these aggregates are very important to soil structure. It gives us porosity. Your ideal soil is going to be one that has 50% pore space. Half of the pore space is air, the other half is water. And then 45% of your soil would be in mineral fraction, and 5% organic matter. When you have that kind of ideal soil, it is resilient to extremes in climate. It will withstand a few harsh years. But if you're already in a system where you have no aggregates, and you have no real biology that's active cause you've used up all the organic matter, it's hard to be able to overcome the forces of erosion that come onto those soils in that kind of environment. It's all about the water in the West.
SR: What’s the next step for dryland cropping systems?
LS: Our hope is that we can introduce cover crops – whether it's a multispecies or single species crop, something that can cover our acres when it's in a fallow period, so that we can build up aggregation, so that we can build up water infiltration. Farmers push back on this to a certain degree based on the wheat yield hit that they perceive or have experienced by putting in a cover crop. But with this new collaborative that we've got going on with CSU in extension of what we've already been doing, we're introducing cover crops to the wheat-fallow system in these long-term rotational experiments in Sterling, Stratton, and Walsh over a catena of soils. We will be able to directly compare over a 6-year time frame, the wheat yields that you get from wheat-fallow no-till vs. wheat-corn-fallow no-till, vs. wheat-summer cover crop... actually I should say that it's a fall planted cover crop, but it's in place of that summerfallow. It's stubble that will be in the field to act as armor and slow down evaporation.
SR: And you mentioned there’s resistance to cover crop adoption out here because of the water limitations, right?
LS: So that's the biggest resistance to accepting cover crops in any big way, because wheat yields are what makes the payments. And they've got to be able to keep their operation economically viable. That's what their concern is.
SR: So what are you hoping to achieve with this research?
LS: I think the answer to this will be when we look at a few years of data across these locations that I've been working on my whole career over 25 years in dryland systems. But I think you'll find from the data we've collected and looked at up to date is that anything is better than just wheat-fallow, even in the dry years. 12 years of our study was in above average temperatures, and the second half of our study was predominantly - say 8 years out of the 12 - drought. Heavy drought. Even through wet and dry years, if we take averages over Sterling all the way to Walsh, everything is beating wheat-fallow. And I think once we figure out what kind of cover crops to recommend, if they're spring planted, fall planted, multispecies, single species… there's so much research that still needs to be done. It's one thing to say that's good for the soil, but the producers have to make the payment to the bank, and we want to have that synergy work together, where the right practice at the right time is going to benefit everything: soil health and the farmers' bottom line.
SR: So you’re hopeful for the future of cover crops out here?
LS: We're seeing really cool ideas come forward that traditionally would have been laughed out of the conference room, right? Cover crops in dryland? uhh out West? And to some degree there is push back to that, but I think it will be exciting to see what we can do. Maybe have systems where we're forage based and we can use cattle or sheep or something where we're mixing it up between just wheat-fallow, but I do believe we gotta keep in mind that this is wheat country and respect why it is wheat country.
Steve Rosenzweig is a PhD Candidate at Colorado State University. This interview was conducted as part of a film project to document emerging innovations in dryland agriculture, which can be viewed here.