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Agriculture --A River Runs Through It

Heather Welch, Claire Rose, and Richard Coupe, U.S. Geological Survey scientists involved in the National Water Quality Assessment (NAWQA) Study of Agricultural Chemical Transport (ACT) study, outline agricultural effects on water quality in the Mississippi Delta region. Topics include research results on nutrient modeling using the SPARROW model, environmental effects of biofuel production, and glyphosate transport.

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Heather Welch:

Grocery shopping for my family is quite easy, we just walk down the street to our local grocery store and there in one place is a large variety of fruits, vegetables, eggs, milk-- all for the taking.

Claire Rose:

On a day-to-day basis what kind of farming concerns that you have to worry about or have to come up with a solution to.

Lawrence Murphy:

Sounds like a question concerning stress. What stresses me the most, we can talk about planting season, irrigation session and harvest season. And I jest, I think I have three annual nervous breakdowns, one prior to planting season, one prior to irrigation season and one prior to harvest season.

Heather Welch:

Some 80 percent of the nation's population lives in urban areas now but everyone has a connection to agriculture. Despite the ever-increasing expectations of high quality, abundant, and inexpensive food many people have little direct contact with the agricultural activities that meet their needs. For many their closest contact with agriculture is shopping at the super market for food and the department store for clothing. It's so easy to buy food and clothing here in the United States but often we don't think about where these things come from until prices go up. Like the recent increases in the price of beef which some might not be aware is actually due to the price of corn for feed going up because of increased demand going up for corn based biofuels.

Richard Coupe:

Heather what part of the Agricultural Chemical Transport study have you really found to be interesting?

Heather Welch:

I think it was more of a spin off from that project, it was we started looking or we were asked to see if we could use the data that we had collected to see if the biofuels initiative had any impact on water quality and quantity in the Mississippi Delta.

Richard Coupe:

What was the biofuels initiative?

Heather Welch:

Well it was implemented by Congress in 2006 and it was to push to make gasoline use up to 15 percent of it needed to be ethanol and in America it's corn-based ethanol. And so we were able to see that between 2006 and 2007 there was a large conversion from cotton in the Delta over 450 thousand acres were converted from cotton to corn the following year in 2007. So the results were we found that in that switch from 2006 to 2007 we increased the loss of storage in the aquifer in the year 2007. We used more water than we would have used had it been in cotton like the year before. Also, we using the SPARROW model saw that we could be increasing the amount of nitrogen yield moving from the Yazoo River basin into the Mississippi River and then on down to the Gulf of Mexico.

Claire Rose:

How have we achieved such an amazingly efficient agricultural system here in the United States? Mechanizations undreamed of just a few years ago are used to increase efficiency and to protect the environment. Giant laser-guided earth-moving machines precisely level vast areas of the landscape to increase irrigation water efficiency. Monstrous farm machines plant, harvest and apply variable rates of fertilizers and pesticides to crops.

Meat is produced on an industrial scale as cows, chickens and pigs that are housed, fed, and kept disease-free throughout their lifetime, while their waste is contained for reuse or environmentally-safe disposal. Modern American agriculture is an efficient and highly productive enterprise that benefits much of the world.

Heather Welch:

However, there are concerns over the effects of agriculture on the environment. For example to optimize production, crops may require irrigation and the application of fertilizers, pesticides and other chemicals. Some of the water and chemicals may leak unintentionally from fields and farm into receiving surface-water bodies. Movement of those chemicals over a field is strongly related to the flow of water over a landscape.

Richard Coupe:

I've been working on fate and transport of glyphosate, glyphosate is a non-selective herbicide used in the United States for crop production. It's been used since the early 1970's but it really took off in the early 1990's when genetically-modified crops specifically corn, cotton and soy bean were modified to, so that you could use glyphosate over the top of them for weed control. And then the amount of glyphosate being used has just jumped up enormously. There hasn't been a lot of work on the fate or transport of glyphosate because it's very difficult to analyze for and very expensive.

But we were able to do a two-year study at two different locations, one in Iowa and Mississippi looking at multiple-size basins. Looking at how the fate and transport of glyphosate changed as you moved in different agricultural and climactic areas. And we were able to sort of relate the occurrence of glyphosate to three different factors, one being use if you, which makes sense if you use it, if you use more of it you're gonna see more of it, and of course in Mississippi because of our warmer climates and our hardier weeds we probably used more than they did in Iowa so we saw more.

Additionally we saw it was related to hydrology or precipitation rainfall, you need water to move agricultural chemicals off the fields. And so in areas where they have more runoff then you'll see more glyphosate. And the third factor was sort of the flow path or the route of the water as it moves off the field and into the stream, does it go through the ground, or does it go through over the top of the landscape. And this makes a difference because glyphosate has a high affinity for absorption to soil particles and if it goes through the ground it has a tendency to absorb more and so you'll see less glyphosate in your stream if the water gets there through the soil.

That's been a very interesting study and it's been quite well received.

Heather Welch:

Here we are in one of the agricultural powerhouses of the United States, an area in Northwestern Mississippi referred to locally as the Delta. Much of the area that we call the Mississippi Delta once looked like this. It was a vast area of bottomland hardwood forest and swamps, teaming with wild life and subject to annual flooding from the Mississippi River.

In order to turn the Delta into the rich agricultural landscape that it is today the swamps were drained, the trees cleared and ditches built to move water off the landscape quickly. In addition, the Mississippi River had to be harnessed by building a series of levies and flood-control structures in order to prevent seasonal flooding in the Delta.

Claire Rose:

Agricultural activities can change the landscape and the way water moves across the landscape. Think about the connection between agricultural activities and environmental concerns like this. Crops and animals have requirements for growth therefore, agriculture meets these requirements. Water, chemicals, and soils can move off of fields into the environment, this can cause unintended consequences.

For example, nitrogen is a natural part of the environment and is applied as a fertilizer to agricultural fields. Nitrogen leaking from agricultural fields and urban areas can cause algal blooms. Nitrogen can cause drinking-water criteria to be exceeded and require expensive treatment of the water source. Excess nitrogen carried by the Mississippi River, some of which comes from agricultural fields in the Mississippi Delta, has been related to an expanding zone of low dissolved oxygen that occurs in the Gulf of Mexico each summer. Other chemicals in agricultural activities may have similar effects on the environment.

Richard Coupe:

Lawrence, over the last couple of years we've worked together on your field, monitoring what's going on. You know why don't you tell us why you would grant us access and let us get in your way and occupy space on your field and take up your time and your effort.

Lawrence Murphy:

As far as the water, I'm interested in what's coming out of our fields, we don't want, we got enough problems in the Gulf Coast with fertilizer, nitrates going down there and increasing that big area where fish are just a dead part in it. I'd like for my son to be here and as long as we can.

Richard Coupe:

So what does a SPARROW model do?

Richard Rebech:

It relates water quality information that we collect in the field to landscape characteristics and sources of a particular pollutant and it also relates it to those things that deliver those pollutants to a receiving strain.

Richard Coupe:

And so what would be the most important results or the most significant results that you found from this study?

Richard Rebech:

The one thing that I thought was real interesting was how much of the nitrogen load was contributed by atmospheric deposition, it was greater than 40 percent. And so with the other sources of nitrogen and phosphorus the higher sources came from the agricultural industry from fertilizer and manure inputs.

Richard Coupe:

Does this relate to the Gulf hypoxia zone at all?

Richard Rebech:

Yes it would have a pretty good affect there, the hypoxia zone in recent studies are pointing toward nutrients as the reasons. And so where in the Southern part of the United States are areas that contribute to the hypoxia zone and we're able to see this as we map the loads for our particular study area.

David Burt:

And that there's off the top two liters.

Mike Manning:

It's a good sample. So that's a composite sample from top to bottom of this section that represents this percentage of flow on this side of the river. So we'll use that sample composited with the other samples we've taken across the river to get our composited sample for the river.

Heather Welch:

We are entering a time of unprecedented demand upon the earth and its resources. There will soon be some 7 billion people all on this single planet needing food to eat and clean water to drink. The demand on agriculture is great and the stakes are high. Can we produce enough food and fuel to meet the needs of the growing population and do so in such a way that it is sustainable and does not affect our air and water quality? This then is the challenge to meet the future goal of feeding an increasing population sustainably will require a cooperative effort between scientists, farmers, policy makers, and consumers.

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Duration: 13:05 minutes