As a farmer perhaps I can add some insight into this issue. Corn is the
crop that generates the most income on my operation and while it is possible
for some operators to produce alternative crops like hay or vegetables, the
economies of production demand that corn be grown in Iowa. There are three
primary methods of applying nitrogen in Iowa. Anhydrous ammonia can be
applied in the fall and with the use of some "preservative" additives this
can be a pretty good method. Anhydrous ammonia can be spring applied before
planting as can either ammonium nitrate which is a white salt like solid or
a urea liquid solution which is a combination of ammonium nitrate and urea.
All three forms of nitrogen can also be applied after the crop is growing.
The application of these products before planting in the spring is probably
the most common method in Iowa. If the soil does not become over saturated
after application the majority of the nitrate stays put and is used by the
corn crop.
Perhaps the best management practice for nitrogen application is to apply
some before the corn is planted and the rest after the corn is growing. The
split application minimizes the chances of nitrates leaving the field but
this can be challenging as adverse weather can prevent later applications
not to mention the fact that additional applications cost money.
This spring we had extremely wet weather which has resulted in very high
nitrate levels in the rivers. As to answering Tom's question as to where
the nitrates are coming from I would suggest that if you could find a graph
of nitrate levels in the river water over time you would get a pretty good
idea of where it is coming from. Being that most of the fertilizer is in
place by late spring or early summer one would expect that the portion of
the contribution would fall off through the rest of the year. I did a
little searching and was unable to find any good charts documenting nitrate
levels on a short enough time scale to implicate agriculture although I am
sure that data of that time scale is available.
My gut instinct is that the majority of the problem we are seeing in Iowa
this year is due to corn production.
What can be done? Later applications of nitrogen would surely help but
these also add expense that the farmer has to incur in extra passes and
equipment. My personal fantasy would be some kind of encapsulated form of
nitrogen that could be applied before planting but would release on a time
schedule regardless of moisture conditions so that the crop could be fed as
needed. I have not heard of any such research happening but who knows? I
once asked an agronomist if he thought that a corn plant would ever be
created that could fix its own nitrogen but he replied that the energy
demands of nitrogen fixation would ensure that such a plant was not
competitive with more traditional types of corn.
Perhaps the simplest short term solution would be to have waterworks
increase their treatment capacity.
Corn production is not perfect by any means, but it does work well in Iowa
and it does contribute greatly to the state's economy. The ultimate answer
is probably a combination of all factors contributing a little to hopefully
get things to a manageable level.
Steve Swan
_____
From: Iowa Discussion, Alerts and Announcements
[mailto:[log in to unmask]] On Behalf Of Pam Mackey-Taylor
Sent: Wednesday, July 17, 2013 1:11 PM
To: [log in to unmask]
Subject: Re: How much nitrate from fertilizer?
Is this a question that could be answered by someone at the Des Moines
Waterworks -- Linda Kinman or Bill Stowe?
pam
-----Original Message-----
From: Thomas Mathews, CIG <[log in to unmask]>
To: IOWA-TOPICS <[log in to unmask]>
Sent: Wed, Jul 17, 2013 1:05 pm
Subject: How much nitrate from fertilizer?
I haven't seen an answer yet to the question in my posting yesterday, so I
assume no one noticed it. So I'll ask again, and rephrase it:
How much of the nitrate that is being removed from the Des Moines water
supply originates from factory farms, and how much comes from farm field
runoff from ammonium nitrate and other nitrate fertilizer applications?
Is it, say, 5% from factory farms and 95% from fertilizer applications other
than hog manure? No, I'm not defending CAFOs. I just want to know.
Neila, maybe this is something you could research?
Thanks,
Tom
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