Challenges For Nitrogen Management

By |

Before I start talking about the environmental challenges, I would like to share some good news. In the early 1970s, we were producing about three-quarters of a bushel of corn per pound of nitrogen (N). Now we are closer to 1.16 bushels of corn per pound of N applied. This reflects a 51% increase in efficiency while we’ve only incurred a 12% increase in fertilizer use. The other good news is that crop prices have improved.

Unfortunately, some people in the environmental science area are concerned that these good prices have caused people in ag to think more liberally about our management than in the past, and they question whether this up-trend in crop output per unit input of N is going to continue because they think when prices are good for corn, ag management practices get sloppy.

Those people don’t know that 40% of the world’s population would not be here if not for our ability to provide food and fiber for their needs through fertilizer. The challenge is that organizations such as the Woods Hole Research Center and other environmental groups are pointing out that we have altered the N cycle as humans on the face of the Earth.

Some of this concern is related to the belief that there is too much reactive N in the environment. Reactive N is derived from a number of different inputs; it can be fossil fuel in origin or N fixation in ag eco-systems. The projections are that this steep curve in reactive N contributions to the environment will continue as the world’s population increases. With this comes an increased burden to try to protect our resources from this reactive N effect.

Increased Usage

There’s no denying the fact that we have increased the use of mineral fertilizers since the 1960s. In fact, half of the mineral N used on the Earth has been utilized since 1985. That has increased the transfer of N through the landscape over background values. What is natural background? According to a National Research Council publication, this was around 1 pound of N per acre per year within the Mississippi River Basin. Some data shows current losses in excess of about 27 pounds of N per acre per year in tile-drained areas within the Mississippi River Basin.

As you increase the N rate above the plateau in agronomic response, you increase the amount that’s not recovered by the crop. There’s a public perception that ag is using more than the recommended amount of N. Is it reality? In some cases, yes. In some cases, no.

EPA has said since March 2006, because of these environmental issues, that it is prudent to start to deal with these issues more directly now. That means everything we do in non-point source nutrient management is under greater scrutiny now that it ever has been before.

As a backdrop, 80% to 85% of our fertilizer market in the U.S. is concen­trated within the Mississippi River Basin. How do we manage within this system? Do we tell everyone to use a broad brush approach and tell everybody to cut back 50%? How many farmers and rural communities could remain economically viable with a 50% cut in N use?

We’ve got to do a better job of managing nutrients. Until now, the concern has been nitrate nitrogen and water quality discharge. Now there’s a possibility that urea could be a concern in estuaries and near-shore coastal areas. Some research suggests that there are some harmful algae species which appear to favor urea as an N source and they grow intensively if urea is the N form available to them. Some of the harmful algae blooms could lead to human health issues, because the naturally-occurring algae toxins are ingested by shellfish and, when consumed by humans, could lead to toxic poisoning. Even inhaling some of the aerosols induced by wave action, which are associated with some of the algae toxins, could be dangerous to humans.

We are working with leading scientists and paying close attention to environmental concerns. If we can get our crops to use the N more effectively, that will hopefully put more money in the farmer’s pocket, and reduce the risk of environmental N loss.

Working To Improve

The Midwest has been the brunt of criticism because of its use of fall-applied N for corn. Because the seed’s not planted until the spring, there’s concern about all this N lying around out there before the crop really reaches its peak N uptake demand. Many wonder what would happen if we did more spring N application and less application in the fall? Some data do indicate if we apply N in the spring for corn instead of the fall, there’s a chance in some systems to reduce that loss by almost 15%. In parts of the Midwest, spring-applied N instead of fall-applied N could cut drainage losses of nitrate N anywhere from zero to 25%.

On a worldwide basis, we are probably not above 40% to 50% efficiency with N use. Stated another way, no more than 40% to 50% of the fertilizer N applied worldwide in a given year is recovered or taken up by most cereal crops that same year.

As environmental pressures increase, we all need to strive to improve nutrient management practices that will enhance crop recovery of applied N. Newer technologies like crop N-sensing and variable-rate (maybe even variable source) N application may become increasingly important tools in the farmer’s and certified crop adviser’s (CCA) toolboxes.

Moving forward, I would challenge each of us to consider ways we can improve fertilizer best management practices to enhance crop nutrient recovery, farm profitability, and to protect water and air resources.

Snyder is nitrogen program director for the International Plant Nutrition Institute, Conway, AR.

Leave a Reply