Managing to Optimize Your Corn Silage Yield After a Difficult Start

by Daniel Hudson, UVM Extension

Excessive rain has likely caused significant leaching and/or denitrification in corn fields.  Recommendations generated by the pre-sidedress nitrate test (PSNT) are not nearly as useful in years when weather is as far from normal as it has been. This is an excellent year to use Adapt-N to generate data-based sidedress nitrogen recommendations for your corn crop.

The current situation
Decent weather in May allowed for timely planting, but with more than 5.5 inches of rain in the last 30 days, we have reason to wonder about how much nitrogen has been leached out of the root-zone in our corn fields.  With cool temperatures, a fair amount of cloudy weather, and nearly saturated soil conditions, the corn has been treading water.

Low milk prices have us wondering where costs can be cut.  Given the desire for full bunker silos, skimping on nitrogen fertilizer is not usually the first or best impulse.  Given recent unusual weather patterns, this is NOT an ideal year to use the pre-sidedress nitrate test (PSNT) to determine your corn nitrogen fertilizer needs. The PSNT is designed to predict sidedress nitrogen fertilizer needs in fairly normal conditions.  It does accurately measure the amount of nitrate present, but the recommendation is based on the assumption that the present nitrate concentration is a good indicator of future nitrogen release from past manure applications.  In a normal year, that assumption works because there is a typical amount of nitrate being released from decomposing manure in those typical conditions, but when abundant precipitation causes nitrate to be leached from the soil, the PSNT report will often come in very low.  In this situation, the PSNT nitrogen recommendation output basically says, “nitrate concentrations are low now and therefore will also be low in the future: apply a whole bunch of nitrogen fertilizer.”   The PSNT does not know whether or how much manure has been applied to that field over the past several years.  Thus, in the context of unusual weather patterns, it also does not know whether there is much more plant-available nitrogen in the ‘microbial pipeline’ or not and therefore it often over-recommends nitrogen fertilizer – sometimes by a lot.

Is there a better alternative to the PSNT?  Yes, I believe there is.  Adapt-N was developed by soil scientists at Cornell, based on a simple (outwardly) concept: given a certain set of information, nitrogen behavior in the soil can be modeled well enough to give an excellent nitrogen fertilizer recommendation for corn production.  This is roughly analogous to the program that your dairy nutritionist uses to balance a ration – ration balancing programs work because the program has been made and validated by scientists who understand a lot about cow and microbe physiology.  Both processes were validated by researchers using trial-and-error.

You served your plate, why not eat?
If you have gone to the trouble of developing a nutrient management plan, you already have all or most of the information that you need to make the Adapt-N program work.  Think about what factors affect the release of nutrients from manure:

  • Environmental conditions: rainfall and temperature over time.  Adapt-N uses the GPS coordinates of your field to inform the program what your weather has been like.  You do not need to manually enter weather data.
  • How much manure?  When?  Was it incorporated? Percent solids?  Ammonium nitrogen content?  Organic nitrogen content?
  • Soil organic matter? Texture?
  • Relative maturity of the corn variety planted?  Population? Expected yield? Date of planting?

The program takes this and other data to predict how much plant-available nitrogen you have in your soil now.  Taking historical weather data into consideration, it also predicts when and how much more nitrogen will be released from past inputs.  Depending on the settings you choose, Adapt-N will send you email updates that will tell you the current nitrogen status of each field.  If you get a leaching event, you will know.  If you are wondering how much was leached, it can give you a data-based estimate.  If you need to take corrective action, it will tell you.

If you are following your nutrient management plan, ‘your plate has been served.’  All the shopping, chopping, and cooking is basically done.  Going the next step and plugging the information into Adapt-N is the easy part.If the recommendation is extremely different from what you expect and you are concerned about losing yield or spending too much on fertilizer, you don’t have to follow it!   You might follow the recommendation on part of your field to see what happens.  In any case, the recommendation is a high-quality data-based piece of information to take into account when making your final decision.  In my experience, the program works very well and should be in every corn grower’s nutrient management tool box.

If you want to check to see whether the recommendation was on-target or not, you can evaluate the accuracy and efficacy of this product by using the PSNT or the late-season stalk nitrate test.  At any given time, Adapt-N can predict what the PSNT should be; at the end of the season.  If the stalk nitrate concentration is significantly outside of the optimal 700-2000 ppm range just before harvest, then there is reason to believe that either the program did not work or the data that was fed into the program was not correct.  That raises the final point: garbage in, garbage out.  The program can be no better than the data that is fed into it.  If your soil testing procedure was not correct, the soil organic matter numbers that are fed into Adapt-N might be incorrect.  If manure sampling was not done properly, some of the most important program inputs will be based on flawed data.

It is rare for anyone in Extension to promote a particular proprietary product.  My reason for doing so in this context is:

  1. The program was developed and is still being refined by Cornell University researchers.  That is to say that there is solid data that supports the product.
  2. There are no competing products on the market that have demonstrated (at least to me) the ability to do what this program does.   If there were, those products would certainly get equal time from me.  If you know of or are steward of such a program, I would be glad to hear about it.

If you have an up-to-date nutrient management plan and would like this product demonstrated on your farm, please contact me ( and I would be glad to work with you to get nitrogen recommendations on up to three of your corn fields.  If you would like to jump in, the product can be purchased at:


About Daniel Hudson

Daniel is an agronomist for University of Vermont Extension in the areas of agriculture and nutrient management.
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