Nitrogen Management

This year in parts of Minnesota there are new regulations taking effect that will regulate nitrogen testing and how much nitrogen can be applied. The goal of the new regulations is to protect ground water, and drinking water.

The Minnesota Department of Ag (MDA) held meetings to talk with farmers about how the new rules might look and how they will affect them. In most parts of the state the new rules will not affect them, but in southern Minnesota, where the MDA feels ground water is more vulnerable, the rules will affect rates that can be applied in those areas. The new regulations are expected to take effect after fall 2018.

The rules are divided into two parts:
 Part 1 is restrictions on the use of N fertilizers in the fall and on frozen soils in vulnerable areas. The exceptions to this are small grains that have been established, pastures, and research areas less than 20 acres.

Part 2 of the rule applies to areas where there are high N levels found in the ground water. According to the MDA 9.5{b4c4b3c31b85440e5ca5306e00628c0f48be4a5135888c167a359bacb50b7c0d} of private wells in the vulnerable areas exceed the nitrate standard. The MDA plans to test up to 70,000 more wells in over 300 town ships by 2019 to see if the problem is lager then thought.

You can see the new regulations and more information at the MDA web site

The next question is, if you are in an area that requires the new management practices what are you required to do? MDA has a local advisory team that you need to contact to find out what practices are required and after four growing seasons farmers can request to have their fields tested to see if ground water levels of N have dropped. If farmers fall in the zones that are to be managed under the new rules the MDA askes that you please submit any questions, comments, and concerns. They also ask that you consider the following questions before you submit.

1. Describe how part 1 and part 2 affect you.
2. Does the description of vulnerable ground seem reasonable for your farm?
3. Are your existing practices protecting the ground water?
4. Should the allowance of 20 pounds of N from MAP or DAP be removed if soil tests are used to determine
P application rates?
5. Are there Precision Ag Technologies that need to be considered in mitigation strategies?
6. If you are in the area affected describe the role of your local advisory team in the mitigation process and
the expertise in you community and its ability to participate on the team.

In the south half of Minnesota where I grew up and have worked most of my life we have always had the same attitude towards N application and how it is used in our crops, mainly corn. When you put N down it’s gone the next year. The recs by the universities and others account 1 to 1½ pounds of N per bushel of yield goal, you could take into account some N credits from soybeans if you wanted. With increasing yields the last few years, the amounts of N application have been getting higher and higher. But is that the right thing to do? We must consider the falling prices of commodities, the price of fertilizer and other inputs vs. how much N is needed to get max yields.

A University of Minnesota study done by Gyles Randall, Michael Schmitt, Jeffrey Strock and John Lamb has been focused on the very question with the purpose of maximizing N rates for corn while also protecting ground water. They studied multiple sites over a period of 7 years in small strip trials and large strip trials. The trials were also across many different field types and varied in application times and amount of N.

The results of what they found may surprise some and will have farmers rethinking about how much N they use, how they put it on and when. They found that when putting on rates ranging from 0-140 pounds of N that the optimal rate of N for the small strip trials to get over 200 bushels per acre was 120 pounds. The findings for the large strip trials were the same. If you would like to read more on the finding the website is:

This brings up many questions, with one being how can they get more bushels of yield then they are putting down pounds of nitrogen? Where is the nitrogen coming from? Have we been wrong in our assumption that no N is available the next year?

Other states around MN have been testing for nitrogen for years and have found that even after you take off a good crop there is N left over in the soil. We have been over applying N for years and years, but didn’t realize it because we never tested the soil to find out. The results are the build up of N in our soils, and I believe that starting this fall with testing for N we will find out that there is N left in our soils. The question will be how much credit do we give to the amounts of N we find there? Also, when and how do we test for it? How do we readjust our application practices to best use it?

First thing we need to consider is testing, how it should be done and what method to use. Another factor to consider is the CSP program, if a farmer is in the program they must use precision sampling. There are two main ways of doing this, Grid sampling and Zone sampling. Both have their strengths and are good methods to use depending on a few outlying factors. Grid samplings one main drawback is the price of the sampling, it tends to be a little more expensive per acre where zone sampling is less expensive. With Nitrogen testing now required in much of SW Minnesota the use of the two will continue to increase, so each farmer will have to weigh what option will work best for them and their farming operation.

Having done most of my ag career in the southern part of MN I can tell you that most testing for Precision Ag is done by grid sampling. Grid sampling does have some good uses, related to manure management and soil pH for instance, but I believe over all that zone sampling is the better way to go. On the average, with a 2.5-acre grid so much can be missed, not to mention the expense and time it takes to do the samples. Zones use years of images, and yield data to come up with what I believe to be a more accurate representation of the field and its trends. Also, it’s a more economical use of money given the current commodity prices for corn and soybeans.

Second thing that I am learning is that what I thought, and many other agronomist and crop consultants have been wrong about is the availability of N after it is applied for the following year, and years to come. If the N was gone as we have thought then the study from the U of M would not have come out with the results that it did, with the yields as the amount applied should have gone down and not up. This also has to do with better hybrids and their ability to use less N to get higher yields, which also results in more N left at the end of the year in the soils.

With the new regulations that apply to SW Minnesota we are going to have to start testing, and adjusting our application rates based off those results. We just need to figure out how much N credit to give based on testing and how much of the N we think will be available for the current cropping year. I don’t think it will be a bad thing in the end to know where are N levels are at. We will continue to get better and better yields, and if we can do that while using less fertilizer, in return we will be saving money, and getting less N into the ground water. It seems to make sense that we should test for N levels.