Sunday, June 28, 2015

Crop Scouting Alerts and Notes on Nitrogen

There, of course, have been many nitrogen deficiency concerns in corn.  I have heard that urea is becoming scarce in the Midwest, as many are beginning to panic.  Prices for urea are all over the place and range from $16 - $50 per acre (increased price includes Agrotain).  During my travels last week (Northern Indiana, Northern Illinois, and Southern Illinois), I unfortunately, visited some of the most flooded areas of my area.  We still remember that areas of Missouri are suffering from floods as well.  According to the latest data, Jim Angel, Illinois State Climatologist, reported that June in Illinois was the seconded highest on record:

CORN NITROGEN:  Most of the yellowing of corn now is due to corn root saturation, so it really is too wet to tell if the crop appears to be suffering from N loss at this time. Some may be testing for soil nitrate levels, but in reality, many don’t take the time to do this as it has rained so much!
·         It really will depend on: 
1.) When was the N applied?
 2.) What fertilizer was used? 
3.) Quantity of N applied? 
 4.) Field conditions after application

  • Spring Anhydrous ammonia (NH3), depending on warm soil temperatures (cooler this spring to the North!) will take about 3 weeks for 20% to become available and 6 weeks for 65% to become Nitrate (usable form for plant uptake), and for you "lucky ducks" that used used N-serve this year, you can subtract about 10% from each of those previous percentages. 
  • Rescue Urea (broadcast) will take about 3 weeks for 50% to become Nitrate (usable form for plant uptake) – therefore it is not recommended for late applications (see my corn growth stage comment below.)
  • Urea ammonium nitrate (UAN) solution can be applied with a banded application (high clearance sprayer/drops) and up to 50% of nitrate is available at application! – But, most fields are too wet for ground applications.
  • Once N is in a nitrate form, then it is susceptible to loss from rain, but usually, most N loss is due to soil temperature during soil saturation (denitrification).
  • Soil temperature 75F to 80F (9 days saturated – 95% nitrate loss of the total N applied)/Soil temperatures 55F to 60F (10 days saturated – 25% nitrate loss of the total N applied)
  • One thought may be to just apply a rescue to low lying areas/flooded areas or fields to save money and the environment.
  • My question to the grower is will N be available for corn during the most critical time? – pollination.  This is why it is very important to know the corn growth stage.  Most of the time, pre-tassel rescue N application have proven effective at recovering yield.  Therefore, rescue N should be applied by silking and as late as 4 weeks post pollination.

It is time to scout for disease. 
CORN DISEASE:  Both Gray leaf spot and Northern corn leaf blight are making their debut in fields.  Northern corn leaf blight showed up 2 weeks earlier than normal this year.