ASA members talk water security
At the American Association for the Advancement of Science (AAAS) meeting in Boston two weeks ago, the American Society of Agronomy (ASA) sponsored a symposium with a lyrical name: Green Dreams, Blue Waves, and Shades of Gray—The Reality of Water. But the session also tackled a serious truth.
While demand for water is increasing rapidly around the globe, water supplies are not.
So, what does this mean for agriculture—one of the planet’s biggest consumers of water—and its ability to feed the world? It’s a critical question, says Fred Vocasek, senior lab agronomist with Servi-Tech, Inc. in Dodge City, KS, and answering it is the goal of the ASA Water Security for Agriculture Task Force that he chairs.
ASA’s science communications staff recently sat down with task force leaders Vocasek, Rattan Lal, and Gary “Pete” Peterson to learn more about water security and why ASA has made it such a priority. What follows is the first segment of a three-part interview.
Let’s start with the term water security. How do you define it?
Rattan: Maybe I can read our task force’s definition. It says:
“Water security is present when all agricultural systems and the people dependent on them have physical, social, economic, and political access to adequate, clean, and safe water at all times to meet the physiological demands for high and sustained water productivity, ecosystem services, and healthy life of people and biota.”
What we really need to indicate is that this definition sounds very similar to some of the published definitions of food security. We tried to draw parallels between the two, so that water security and food security are kind of two sides of the same coin, if you want to put it that way.
So, of all the issues ASA could have chosen to focus on, why water security?
Fred: As you look around the landscape, a lot of people are involved in water issues: hydrologists, geologists, regulators, engineers. But in food production and agronomy—that’s where the water, the soil, and the plant root all come together, and that’s where we live and breathe. So I think we’re in a unique position as scientists and as practitioners to address some of the issues.
Rattan: I would add that water has no alternative. We have alternatives for oil and other resources, but water we must have—there is really no substitute for it. And at present water is a very scarce commodity, and it’s going to become even more scarce with the extreme events of climate change, such as what happened in the U.S. last summer. This drought that we are experiencing in the U.S. is a century drought. Really nothing like this has been experienced for over 80 years or more, and it’s due to the scarcity of water in the root zone. So, water security is really a very critical issue of the 21st century, and I think it is a very timely issue for the American Society of Agronomy to address.
It’s been widely publicized that agriculture is one of the world’s largest users of water. Is this why it’s so important for ag to be part of the solution?
Rattan: Yes, agriculture has been the largest user of water to, let’s say, the end of the 20th century. But now there’s tremendous competition coming from industry, urbanization, recreation. So because of that competition, agriculture is getting less and less water. Recently, a lot of competition is coming from the fracking industry, where farmers in western Colorado and elsewhere are now competing for water with people who can buy it at a much higher price, and therefore the farmers are suffering from that competition.
So, agriculture being among the largest users and facing stiff competition must make much more efficient use of water than we have in the past. The past has been luxury consumption, but now every drop of water counts. Every drop that falls on agricultural soil must be used to produce crop grains. The agricultural productivity per unit of water—what we call water productivity—has become a very crucial issue.
Fred: We’re going to have to work each drop of water to death.
When we talk about working each drop of water to death, are we mainly talking about the efficiency of irrigation?
Pete: Water use efficiency encompasses more than irrigation. There’s also efficient use of precipitation, because an awful lot of the world doesn’t use irrigation. And parts of the world aren’t getting good crop yields because they don’t know how to efficiently use the precipitation they receive. There are a lot of people in the U.S. even—in Colorado, in particular—who aren’t very good at using the precipitation they receive.
Fred: Pete hits on a good point because when you talk about agriculture, irrigation is the first thing that comes to mind, and if you’re west of the Mississippi, it’s a real common issue. But even though the Eastern part of the U.S. has much less irrigation, there are still water security problems and competition. If I store a gallon of water in [the soil] of my field, that’s a gallon of water that doesn’t get to a lake, doesn’t get to a stream, where it might be available for use by somebody else.
Rattan: I think another issue that really requires more attention is salinity. Right now in the U.S. and globally, 17 percent of the irrigated cropland produces about 40 percent of our total agricultural production. The problem is many of the groundwater sources are brackish in semiarid regions where irrigation is practiced, and that causes salinization of the soil. Australia is a very good example. The Southwestern United States is another example. Also, India, Pakistan, and China, where irrigation is a major way to produce food, and salinity and water-logging occur if drainage is not taken care of.
So this issue will become of more and more concern, and it can also be addressed by judicious use of irrigation water.
What are some other ways to make better use of water?
Rattan: We haven’t talked yet about conserving water in the root zone. When water falls from the sky, it’s added as a supplementary form of irrigation. But if it is lost through evaporation, or if it is lost as surface runoff or as deep seepage, then the water storage capacity of the root zone is decreased. So somehow we need to conserve water in the root zone, and, Pete, I think you really need to say some of the good things that you guys have done in Colorado.
Pete: Yes, it’s one of the issues that we have in dry areas…where Rattan lives in Ohio it may not be quite as critical.
Rattan: Except last year. (laughs)
Pete: For example, the conversion from bare soil to some kind of conservation tillage or no-till system where you keep residues on top, does two major things: It decreases evaporation, which does what Rattan says—it helps retain water in the root zone. And the other thing it does is protects the surface so that when the rain does fall or the snow melts, you can actually get that water into the soil because the energy of the raindrop is dispersed, and the water has a chance to get in without running off.
By the way, with today’s high fuel costs, farmers have wanted to reduce tillage, so they have automatically moved in the direction of high-residue farming because herbicides cost less than diesel fuel. Money and economics are a big part of whether or not you get change.
Rattan: Last year, we had an experiment at Coshocton, Ohio, where we experimented with removal of residues from no-till plots for cellulosic ethanol production. So we had one no-till plot with zero residue; another with a normal amount of residue; and a third no-till plot where the residue was double.
Well, last year we had a very serious drought, and the crop growth yield was exactly in proportion to the amount of residue. I have pictures of the plots. Under zero percent residue, the corn really suffered; at 100 percent it was in between; and at 200% we got the best corn. (However, crop stand was affected by heavy crop residues because of poor germination).
And our long-term no-till experiments at Wooster show exactly same thing: Under no-till with residue, corn and soybeans are doing very well, and the one where the residue is plowed under—not removed, plowed under—yield is very mid-level.
So I think what this says is that conserving water in the root zone makes a system resilient to extreme weather events such as the drought of last year.
Pete: It’s kind of like a buffer. The only problem in Colorado last year was that it didn’t rain. So, even the people who practice no-till didn’t have any water to save.
Read part two, a discussion of how water supplies can be secured: By conserving "blue" water, maximizing "green" water, and reusing the "gray" and "black."