Gulf Dead Zones Directly Tied To Tile Drainage Systems, Boon To Crops In Delta & Elsewhere In Basin

[hatrack]

cienceDaily (Sep. 27, 2010) — Tile drainage in the Mississippi Basin is one of the great advances of the 19th and 20th centuries, allowing highly productive agriculture in what was once land too wet to farm. In fact, installation of new tile systems continues every year, because it leads to increased crop yields. But a recent study shows that the most heavily tile-drained areas of North America are also the largest contributing source of nitrate to the Gulf of Mexico, leading to seasonal hypoxia. In the summer of 2010 this dead zone in the Gulf spanned over 7,000 square miles.

Scientists from the U of I and Cornell University compiled information on each county in the Mississippi River basin including crop acreage and yields, fertilizer inputs, atmospheric deposition, number of people, and livestock to calculate all nitrogen inputs and outputs from 1997 to 2006. For 153 watersheds in the basin, they also used measurements of nitrate concentration and flow in streams, which allowed them to develop a statistical model that explained 83 percent of the variation in springtime nitrate flow in the monitored streams. The greatest nitrate loss to streams corresponded to the highly productive, tile-drained cornbelt from southwest Minnesota across Iowa, Illinois, Indiana, and Ohio.

This area of the basin has extensive row cropping of fertilized corn and soybeans, a flat landscape with tile drainage, and channelized ditches and streams to facilitate drainage.

"Farmers are not to blame," said University of Illinois researcher Mark David. "They are using the same amount of nitrogen as they were 30 years ago and getting much higher corn yields, but we have created a very leaky agricultural system. This allows nitrate to move quickly from fields into ditches and on to the Gulf of Mexico. We need policies that reward farmers to help correct the problem." David is a biogeochemist who has been studying the issue since 1993. "We've had data from smaller watersheds for some time, but this new study includes data from the entire Mississippi Basin. It shows clearly where across the entire basin the sources of nitrate are.

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http://www.sciencedaily.com/releases/2010/09/100927122225.htm

[TheWraith]

1. Why aren't we harvesting the algae blooms instead?

They're useful biomass for converting to fuel.

[TheMadMonk]

2. Too difuse to get before it does the damage and by the time it's harvestable...

...it's too late.

The trick would be to get to that drainage water before it hits the ocean and pull the nitrates out. Wetlands would be a good place to start. Slice off that ludicrous Mississippi mouth, rebuild and revegetate barrier islands. Fill in the space behind with salt marshes. Dam the last little bit of the Mississippi and divert outflow into those wetlands and marshes.

We geoengineer, almost with out thought for convenience and profit. Isn't it time we did it for the environment?

[kristopher]

3. wiki on tile drainage

http://en.wikipedia.org/wiki/Tile_drainage

From the article: "David said that ripping out all of the drainage tiles is not a viable option. "Creating wetlands and reservoirs such as Lake Shelbyville can remove nitrate by holding the water back and letting natural processes remove it, but that's not a solution. It's expensive and we can't flood everyone's land to stop nitrate. That's not going to happen.""

Their assertion regarding the same level of nitrates being used now as was used 30 years ago seems like an odd way to put it. It sounds like an evasion to a question that is easy to answer - are the farmers applying more nitrates than is needed? A major problem for industrial farming is the disposal of animal wastes. One of the favored ways to dispose of it is to spread it on the fields and let it wash through the system.

This is a regulated practice (EPA?) but as usual, during the Bush years there was no enforcement.

It may be technically accurate to identify the drainage system as an observable participant in the event of nutrient runoff, but it seems damned convenient that they gloss over the part of the problem that has a correctable human element to focus attention on an infrastructure issue that can't help but make most people accept the status quo.

I'd like to see an analysis of what type riparian border would be required to reduce the nutrient load in the streams by 80%.

[Nihil]

4. Good point.

> It may be technically accurate to identify the drainage system as an observable
> participant in the event of nutrient runoff, but it seems damned convenient that
> they gloss over the part of the problem that has a correctable human element to
> focus attention on an infrastructure issue that can't help but make most people
> accept the status quo.

Hmmm.

[Iterate]

5. Wrong:"ripping out drainage tiles"

The line "ripping out all of the drainage tiles is not a viable option" might make a nice image of an obvious impossibility, but it has no basis in real life.

The large sections of the upper Midwest are ecologically the "prairie pothole" region, with a very high mean water table and many small areas of sunken ground -depressions left from glacial retreat. The tiles are very shallow, so that two guys with a trencher/backhoe could cut the tiles for an entire farm in a single day. Come the next good rain those potholes will be full.

The restoration of the pothole ecosystem can be elaborate, but need not be. Aggressive and non-native species will colonize first (some of which have become herbicide tolerant), but restoring the biodiversity can be considered a secondary and long-term goal. At least the biologists would have something to work with and the filtration can begin.

Variations of this plan have been proposed in the past 40 years as an alternative to large dams, so there is plenty of research already completed. Here's one:
"Long-term vegetation development of restored prairie pothole wetlands "
http://www.springerlink.com/content/g13q208127x524u3/

Fertilizer. Well the best data I could find right now comes from 1993, some time after the nitrates infiltrated well water and started killing babies on farms. The solution was to amplify the migration off the family farm and to move the babies into the towns.

"Each year, there are 8 billion pounds more nitrogen available in farm fields than can be used by the crops growing on this land (NRC 1993)."
"Nitrate Contamination of Drinking Water"
http://www.ewg.org/reports/nitrate

The thing you have to realize here is that farmers may work the farm, but it's the bankers who run them. They say what will be planted, and how it will be fertilized. The bank hires farm managers to look at the soil tests and to see that the recommended amounts are applied. No one will risk being accused of skimping.

Anecdote: I talked to one farmer who was told by his banker that he couldn't have a horse on his farm for his kids unless he could show that it was part of a profitable breeding plan. Not uncommon. This was during the farm debt crisis of the 1980's, but as far as I know it's still true.

Animal Waste. The image of a lone farmer mucking out a barn and spreading it on a field is so old now as to be quaint. Rather, imagine a leaky lagoon full of sewage equal to the production of a medium-sized city being trucked out and dumped in a field on a single day. It is impressive enough to drive the few holdouts off the neighboring farms and into town. Farmers don't have livestock, corporations do, and they do it in multiples of 10,000 at a given location. It is not regulated as sewage would be. If they had to pay for real sewage treatment, proper wages, the full cost of the road network and trucking, and non-subsidized grain, I have my doubts as to whether the operations would be profitable and we might have better pork for the effort. Almost everyone here already knows this, but I've enjoyed typing it again.

I admit I'm not up-to-date though on the current sewage regulations or enforcement and I don't want to be. Someone else can step in, so to speak.

Riparian border. Your last question is the easiest, as I remember one study in particular, done by ISU extension in the 1980's or so showed that a simple strip of short perennial grass 2-3 meters wide was sufficient for a high filtration and soil retention. More important was the use of the grass strip upland in the watershed to control runoff. I would imagine sources for this are available from every ag uni and field extension, as it's been duplicated many times, many places.

Each step mentioned here has been known and fought over for decades now.

Should anyone be so foolish as to advocate something so rational and cost-effective it's obvious who your enemies would be: from Grassley to King to the same damn Governor, to the bankers and suppliers, to Monsanto and the meat packing plants. But you might be forgetting one of worst, Jack "the bad egg" DeCoster, (yes, that guy) who first made his big fortunes in building otherwise unwanted large hog lots in the 1980's in Iowa. He was "bullet proof" then, had layers of unseen protection, and I doubt anything has changed.