Tuesday, February 25, 2020

Last Thursday (2/20/20) the Iowa Soybean Association (ISA) released the results of a study1 showing Iowa farmers could save up to $99 million per year by better aligning their fertilizer amounts with corn requirements. Among other things, their data show that surveyed farmers were applying about 34 pounds per acre more nitrogen fertilizer than ISU recommendations (140 pounds per acre) for corn grown after soybeans.

The content of the report was not a surprise to me and likely not to anyone that has spent much time studying issues related to nitrogen fertilizer and nitrate pollution in our streams and lakes. The Iowa Nutrient Research and Education Council (INREC), an arm of the Agribusiness Association of Iowa (AAI), reported2 in June that their survey data showed nitrogen rates to corn following soybean (c/sb) averaged 169 pounds per acre, similar to the ISA data (174 pounds per acre). For corn grown following corn (c/c) the previous year (usually about 1/10th to 1/5th of Iowa crop acres) rates are typically higher.

Using sales data, I’ve estimated that the overall rate to corn is 189 pounds per acre, and this includes both c/sb and c/c combined. With this analysis I make an admittedly fragile assumption that all commercial nitrogen fertilizer is being applied to corn. Some is probably applied to soybeans and pasture, but until somebody coughs up some credible data on this questionable practice (at least in the case of soybeans), I think I am being as fair as I need to be.

Bear in mind that so far none of this data considers manured fields, where rates are substantially higher. In a paper3 published four years ago, my coauthors and I used farmer reported data from 768 Raccoon River Watershed fields to calculate the rates shown in the table below, all higher than ISU recommendations.

Recommended N rates

Some farmers are able to generate impressive corn yields with modest nitrogen applications. One is Mitch Hora who farms south of here in Washington County. You can check out his blog4 and read how he grows 196 bushel per acre corn (about the statewide average) with 140 pounds per acre of nitrogen.

With examples like Mr. Hora scattered here and there, Average Joe and Mary can reasonably ask why we use more nitrogen than needed. The calculus on this is very simple: while the farmer absorbs the consequences of too little nitrogen, the public must absorb the consequences of too much, with these latter consequences being degraded water.

In fact, the calculus is SO simple and SO easy to understand that the industry has been compelled to construct a rhetorical brick firewall to hide it, one where the bricks are stamped with “spooning it on” and “we all want clean water.” Another good one is that “nitrogen is expensive” which is spectacularly untrue considering that we still waste about 25% of it (or more) in some years and after 180 years of Iowa agriculture, the first case of nitrogen-loss-caused farmer bankruptcy has yet to be recorded, at least to my knowledge. Maybe there’s one out there, I don’t know.

This is all so comprehendible that I think a malaise about nitrogen rates has permeated much of the scientific community. A sort of a "who cares, it's boring" attitude. Indeed, scientists have been writing about the disconnect between fertilizer (manure and commercial) inputs and crop needs for decades, and there is disagreement about how important it is in the grand scheme of things. The Iowa Nutrient Reduction Strategy science assessment assigned a potential benefit to our streams from better fertilizer management of 10%.

Now it should be said that eight years after the fact, a 10% improvement would sound like sensational progress, considering that we can’t even manage to get on the good side of zero. Stream nitrate levels continue to get worse, a lot worse. More manure generated by more and more animals is not affecting sales of commercial fertilizer, at least not much, and thousands of miles of new drain tile are installed every year that help move the wasted nitrogen to our streams.

Am I crazy to suggest that agriculture get fertilizer inputs under control before asking the public for more money?

Continuing to talk about this at times feels purposeless. It seems to me that many of us scientists have turned our back on the flames and find peace of mind by studying the details. We’ve handed over the fire-fighting to the engineers, hoping they can stop the spreading blaze by building expensive solutions that only the aggregated wealth of the public can afford. Quite the convenient arrangement for the industry, I must say. Keep over-selling the pollutant, and let the public deal with the consequences. Ring me up about a bridge I’ve got for sale if you think anything short of a law will end that arrangement.

But yes, I do think somebody needs to continue to talk about this. Iowa is poised to raise its sales tax $0.01, in large part to fund water quality projects. My unscientific impression is that most people agree with this in principle. Is this public cooperation sustainable when the industry has an unregulated license to do as they please with fertilizer inputs? Is it sustainable when the trade group representing the retailers selling fertilizer has funding from the Iowa legislature to be the "official" measurer of water quality progress in Iowa? Is it sustainable when the degradation of our water continues unabated?

Does anybody care if it’s sustainable, or is this just one more can-kicking down the road to nowhere?

Some people ask me why I write these essays and honestly, I ask myself that pretty often. I don’t believe in having heroes, but I like Orwell’s writing a lot. He said there are four reasons to write: ego, aestheticism, to record history, and a desire to push society in a certain direction. I’m not sure any of those work for me; the last one comes closest but I have resigned myself to the futility of this. I suppose what works for me best are the words of another English writer, Ted Hughes: It’s about trying to take fuller possession of the reality of your life.


2Meeting of the Water Resources Coordinating Council, June, 2019, Altoona, Iowa.

3Jones, C.S., Seeman, A., Kyveryga, P.M., Schilling, K.E., Kiel, A., Chan, K.S. and Wolter, C.F., 2016. Crop rotation and Raccoon River nitrate. Journal of Soil and Water Conservation71(3), pp.206-219.

4Continuum Ag, LLC. October 30, 2019. 60-INCH CORN TRIAL 2019. https://continuumagllc.com/uncategorized/60-inch-corn-trial-summary/.