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Precise Conservation

Is there a flu shot for partially drained depressional areas?

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Can we prevent nitrate leaching or reduce greenhouse gasses with an effective, innocuous, simple and inexpensive conservation practices?

Each year, my pharmacist, Dr. Jennifer Filloon, demands that I get a flu shot; no excuses.  Flu shots are truly a part of precision medicine.  Flu shots are designed to do one thing – prevent the flu. And the benefits are clear:

The flu shot targets seasonal flu strains predicted by researchers.
The flu shot has no appreciable side effects.
Getting an annual flu shot boosts immunity to the flu and can prevent, or minimize, the flu.
Getting the flu shot is simple and inexpensive.

In a recent webinar, Dr. Steven Hall (Assistant Professor of Department of Ecology, Evolution, and Organismal Biology at Iowa State University) talked about the disproportionate environmental impacts from partially drained prairie potholes.  In Iowa, these depressional areas comprise about 9% of the Des Moines Lobe, a geologic region in central Iowa where prairie potholes have been drained and cropped.  Dr. Hall shared with me the early results of his research on this region, which shows that farmed depressions (former prairie potholes) can potentially contribute 3 to 4 times more nitrates to water (on a per acre basis) than the adjacent uplands.  Additionally, Dr. Hall’s findings indicate these poorly drained potholes contribute a disproportionate quantity of greenhouse gases, to our atmosphere, in the form of nitrous oxide.

These depressions start with a 3-fold level of extractable soil nitrate over the adjacent uplands even at peak growing times.  Dr. Hall says this condition is even further amplified, when the excess water stunted or completely drown out the crop.  There is little or no vegetation left to utilize the available nitrogen. 

Now, if only we could prevent against the negative effects of poorly drained depressional areas, like we do for influenza. Could we prevent nitrate leaching or reduce greenhouse gasses with an effective, innocuous, simple and inexpensive conservation practices? What if we inoculated the cropped prairie pothole regions with precision conservation, year after year, after year? Would it make a difference?

Unfortunately, scientists do not yet have enough data to recommend a precision conservation solution, analogous to a flu shot; which likely precludes a one-size-fits-all solution. Instead, farm-specific situations will be critical to consider when trying to mitigate the effects of cropping pothole regions. But Dr. Hall is encouraged and speaks about current research that will help us understand how to better treat these areas. He suggests at least 4 possible solutions:

Conservation tillage: Improve soil structure to achieve better infiltration of water.
Improve drainage of upland wetlands and offset impacts with downstream restored or constructed wetlands at tile outlets.
Return to natural wetlands conditions (CRP or other perennial vegetation mixes).
Plant Flood-tolerant crops, including vegetation for use as biomass energy feedstocks.

Solution #1: Conservation tillage to improve soil structure thereby increase water infiltration. 

If the crop is stressed or drowns out from saturated or flooded conditions, less nitrogen is removed from the system dramatically increasing the likelihood of leaching or denitrification.

In theory, increased soil health will lead to less saturated conditions; creating a healthier environment for the crop.  The healthier crop will better utilize the available nitrogen.  When less nitrogen is available less nitrogen will leach or be emitted as nitrous oxide.

Our tiling systems in the Des Moines lobe is undersized.  If a large percentage of farmers go to conservation tillage, improving infiltration, it will only further overload the tile system somewhere else, just transferring the problem.  There may be no positive net gain from this strategy. 

Solution #2: Improve drainage of upland wetlands and offset impacts with downstream (CREP) wetlands.
The tile drainage in most prairie potholes is under-designed. Like Solution #1 if we can create a healthier environment for our crops, those crops can utilize the available nitrogen in a more efficient manner. This could lead to less nitrogen leaching and denitrification. To mitigate the effects of increase tiling downstream (CREP) wetlands could be developed. 

Better drainage of prairie potholes will likely lead to better yields and better profitability for the farmer.
Less stressed crops will lead to better nitrogen utilization. 
On a per pound basis, of nitrogen removal, downstream (CREP) wetlands may be the most cost-effective practice we have in our toolbox.  Likely, it is significantly cheaper to install a few downstream wetlands vs. restoring numerous upland prairie potholes. 
These downstream CREP wetlands often reduce the pressure on the upstream tiling systems, creating a circular effect of better draining the upland prairie potholes.
These downstream (CREP) wetlands provide significant wildlife habitat.

The initial out-of-pock costs for developing these downstream (CREP) wetlands are very expensive. The typical downstream (CREP) wetland requires an average of 45 acres.  At $10,000/acre, these wetlands require nearly $1/2 million of upfront investment.  Annually, it doesn’t take many of these wetlands to drain an entire conservation budget.   
The downstream (CREP) wetlands require specific landscape conditions.  These wetlands cannot be built just anywhere.  Finding the combination of a willing landowner and the out-of-pocket cost can be challenging.

Solution #3: Return prairie potholes to natural wetlands conditions

If the crops are being stressed or drown out, then returning these potholes to native conditions could reduce the loss of nitrogen. 
Farmers will not apply commercial nitrogen to these areas. 
Depending on the specific site, it may be more cost effective to not farm these areas. 
These areas will significantly add to wildlife habitat.

When these prairie potholes are returned to wetlands, they are hard to farm around. If they are dry enough, likely the farmer will drive through them enough severely stunting or killing the vegetation.
It is unlikely farmers will give up cropland without some type of incentive program like CRP.  And if these incentive programs are not permanent (CRP is typically 10 to 15 years) then this will not be a permanent solution. 
And if the prairie pothole (and surrounding area) is saturated, and not flooded, the wetlands might continue to emit greenhouse gasses, albeit at a lesser rate, regardless of the vegetation. 
In most cases these prairie potholes are in flat topographies.  Inundating these potholes may cause adjacent farmland, a bit higher on the landscape, to become saturated. This again will lead to stressed or drown out crops adjacent to the wetland just moving the problem of leaching and denitrification further upland.

Solution #4: Plant and harvest flood-tolerant crops and use the vegetation for biomass energy feedstocks

Most of us desire renewable biofuels. The planting of a flood tolerant crop that can be used as a cellulosic (or combustion) energy source holds great promise.

The economics of cellulosic vegetation is largely unproven. 
Developing a third crop is far more difficult that it appears.  Harvesting vegetation in saturated or flooded conditions will require completely new planting and harvesting equipment. 
This is a long-term strategy with great promise and plenty of opportunity to fail.
Just because it is difficult…
If we are going to solve our water quality issues it is clear, we need to focus on these areas that contribute disproportionate levels of pollution. If these poorly drained depressional areas are contributing 3 to 4 times more nitrogen to our water and air, than the adjacent uplands, we simply cannot ignore them. However, in my conversations with Dr. Hall, all potential solutions have substantial associated costs and trade-offs.  We have not yet identified the simple and effective flu shot.  For now, our best recommendation will depend on the site-specific conditions.

The opinions of the author are not necessarily those of Corn+Soybean Digest or Farm Progress.

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