Ways to assure your corn crop that's beautiful in June lives and yields its full potential in October

Corn growers who've seen saturating rainfalls this month have accelerated their soil nitrogen tests and followed through with streaming or dry nitrogen applications. Here's what some top agronomic advisors recommend now, so you can make the most of a strong seasonal start.

June 21, 2018 — Here are their key points to keep corn vigorous and healthy through filling, rather than seeing it fade into premature death in late August or early September.

Dave Schwartz at farmers' field day on his farm

1. First, take several soil tests of your soil nitrogen profile — both nitrate and ammonium. Dave Schwartz of Verdesian Life Sciences takes cores from the surface to 12 inches deep, then a second set of cores 12 to 24 inches deep. Dave adds, "That would especially important on lighter or sandier soils."  

The reading from the second core, 12 to 24 inches, is significant because by now, corn roots are reaching down well into the soil profile.

Ask your lab for the complete nitrogen profile results. Dave wants to see the parts per million total — nitrate plus ammonium — add up to 80 ppm and preferably 100 ppm as a minimum. 

With recent moisture and warmer weather in many Corn Belt areas, Dave notes that much of the conversion of N from last season's crop residues may be already winding down. That would mean that later "feeding" from biological conversion of organic residue to plant-available form is being spent early. With good moisture in the bank, you may want to push the nitrogen rate a tad.

2. Using your soil tests as a guide, follow up with the appropriate rates of liquid N streamed near the rows, preferably with Y-drops. Or broadcast urea or ammonium sulfate over the top.

3. Important: Use a nitrogen stabilizer which restrains conversion of ammonium N to nitrate without killing off beneficial soil organisms which speed the conversion to leachable forms of N. One of those is Nutrisphere from Verdesian Life Sciences.  We don't sell it, but we've seen results of prolonging the effective life and filling days for corn. 

4. If you stream on 28% or 32% nitrogen, add 3 ounces per acre of WakeUP with the liquid. Normally for in-furrow use we recommend WakeUP Spring, but when applied on top of the ground with nitrogen, either WakeUP Spring or WakeUP Summer will enhance root uptake of the nitrogen. About eight years ago, we were surprised to learn that Southeastern farmers were applying WakeUP this way, tank-mixed with streaming and side-dressed 28% UAN. One North Carolina grower observed substantially greater crop response. In that addictive North Carolina accent, he said, "Y'all outa know that WakeUP opens the trap door on those roots and they really take in the nitrogen."

Iowa crop consultant Bob Streit's latest advisory sent to his clients offers these insights on nitrogen loss:

 "One of the next issues that will have people guessing the best course of action will be how to judge the amount of Nitrogen that may have been lost to leaching or volitalization. It can go down or go up depending on conditions. The rule of thumb is that there can be 5% to 7% yield loss per each day the ground temp is above 50 F and the soils are saturated. For many the month of May was very dry and there were few areas with problems. Now in the last two weeks there has been an increasing number of acres that could have lost a sizeable percentage of spring applied UAN or 82% that would have converted to NO3-N.
       
"This is why there are more supporters of the use of N stabilizers that keep nitrogen in the ammonia rather than converting it to the nitrate form. Even for the operators who use Y drops or urea for sidedress or topdress, the use of a stabilizer mixed in with the UAN or Urea being applied later in the season could likely justify using a half rate of a good stabilizer to prevent lost N if a big rain hits and major amounts of ponding occur. Corn plants can access ammonia as well as they do nitrate N. The latest findings have actually shown that arbuscular mycorrhizal fungal strands can actually take up nitrogen in the amino acid form.
 
"If some of your corn was a candidate for having lost nitrogen it may be wise to spend $269 on an atLEAF CHL PLUS meter so you can take chlorophyll measurements on the plants in your fields to see if the levels of greenness stay above 55 or run the chance of dropping below that critical level. If the levels drop below 55 before the plants have reached the late dough stage, it will be necessary to either get a high clearance sprayer with Y drops into the field or research the use of nitrogen fixing bacteria of the Azotobacter crococum or vinlandii species to fix another 50 to 60 lbs of N."

AgriEnergy Resources agronomists also encourage a careful appraisal of nitrogen, and applying more as needed. We've pulled the excerpts below from the latest "Ground Work" e-mail letter sent to AgriEnergy clients:

"A nitrogen deficiency can steal yield in crops quicker than a shortage of any other nutrient. The rainy weather that many of us are experiencing this spring has made nitrogen management a real challenge. 

"Loss occurs mainly from leaching or denitrification. Ammonium forms of nitrogen are converted to nitrate nitrogen when soil temperatures are above 50 degrees, through a bacterial process called nitrification. Once the nitrogen is in the nitrate form it is subject to leaching, particularly on coarse textured soils.

"Also, "denitrification" is a bacterial process that takes place in anaerobic soil conditions caused by saturated soils. Nitrate nitrogen is converted to nitrogen gas and lost to the atmosphere.

"We have also seen additional nitrogen pay off if you experience a heavy rainfall event immediately after a sidedress application or if you have excessive June rainfall. Dribble applications with high clearance rigs are usually successful, even though the nitrogen does not get mechanically incorporated. Applying liquids where the soil surface is moist or getting rain after the application will ensure that you benefit from the nitrogen application. It is good to add complex carbons to the mix. This would include products such as Bio Humus, Activator II, Liquid Sugars, Molasses, Drammatic Fish, and SP-1™. This application also allows the chance to apply potassium and/or other nutrients that might be deficient. 

"This season is reminding us of 2015, when we did not realize the susceptibility of organic nitrogens to N loss. We are told that manure mineralizes and comes available quite slowly. But in 2015, many observed nitrogen deficiency and a lack of nitrogen supply in June. Organic forms convert to nitrate and will be rapidly leached with excess moisture."