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Thursday, February 21, 2013

Nitrogen Rates

Are you still calculating your Nitrogen Rates based on 1.2 Times your expected yield?  That is only the start of what your might want to consider in deciding how much nitrogen to apply.  How much was left from last year?  You can find out by running a pre-sidedress test after corn is out of the ground.  What is your soil contribution to Nitrogen requirements?  The Illinois Amino Nitrogen test is supposed to tell you the answer.  We also have a proprietary test available to use.  Can you consider organic matter content of the soil?  Your soil releases a little over 20 pounds of N for each percentage point of organic matter.  Conservatively, you might be able to count on half of that as being released at a time that it would be usable to the crop.  What about credits?  Soybeans can be credited with 0 to 40 pounds per acres, but it is hard to determine where you should be.  Red Clover has about 60 pounds of N available.  Crimson Clover can be higher.  Hairy Vetch adds about 100 pounds of N.  Should I consider price?    Illinois Agronomy Handbook says to use the N-Rate Calculator.  The N-rate calculator figures your maximum return to N (MRTN) based on years of research.  All the Midwestern states have usable information on that web site.  Illinois has 3 zones to use.  I tell people south of Springfield to use the Southern Illinois rate if they are on light colored soils.  The calculator gives you an acceptable range to use.  Again I would tell you on light colored soils to go with the high end.  You can run a single scenario or if you click on the multiple scenarios tab you can run up to 4 scenarios.   Examples below assume a price for Anhydrous Ammonia at $820 per ton with various prices.  The top shows corn after soybeans rates and the bottom shows corn after corn rates.  Notice how the rate increases as the expected price increases.  I really feel that the N-rate calculator is not as useful if you are using manure, but it is the "legal" method because it is really the only recommendation recognized in Illinois Agronomy Handbook unless you use some sort of Nitrogen Soil Test.  If you are using manure, be sure to figure mineralization based on type of manure and method applied too.  The link above takes you to the N-rate Calculator site.  Click on pictures below to enlarge them. 

N Rate Corn after Soybeans

N Rate Corn after Corn

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