- Be sure to use the correct nitrogen source when applying nitrogen in the fall. Acceptable sources for fall application (north of Rt. 16 & Rt. 36) include:
o Manure (Incorporated): Manures should not be applied in the Fall before soil temperatures are 40 degrees to minimize N losses.
o Ammonium Sulfate: Not in Missouri and not on ground with more than a five percent slope
o Related Side Note: Missouri and Illinois recommend anhydrous as the primary fall applied Nitrogen source.
- Be conscious of soil temperature and conditions not calendar date when applying fall anhydrous:
o Illinois, Indiana, Iowa, and Wisconsin do not recommend applying anhydrous ammonia until soils have trended toward 50 degrees F at 4 inches deep. Risk of N loss is too great previous to such temperatures.
o Missouri does not recommend applying anhydrous ammonia until soils have at least trended toward 50 degrees F at 4 inches deep (with 40 degrees F preferred to further reduce N losses).
o Illinois, Indiana, Iowa, Missouri, and Wisconsin all note that anhydrous should not be applied if conditions do not favor slot closure (due to the risk of N loss). Missouri recommends no anhydrous application when soils are wet (due to the risk of poor slot closure and associated N loss).
o Related Side Note: Only apply anhydrous in the Fall if you will be using a nitrification inhibitor.
- Fall nitrogen, if applied, should be in the form of anhydrous ammonia. Do not apply fall nitrogen if you are:
o Farming sandy soils.
o Farming gumbo soils in Missouri.
o Farming in the Missouri River Bottoms (these tend to be high pH soils which are prone to more rapid N loss).
o Farming ground south of, or in proximity to, Route 16 in Illinois (the southern portion of Illinois is too warm during the fall/winter/spring which encourages substantial N loss).
o Farming ground in the bootheel of Missouri (the bootheel should only be using spring side dress N applications).
o Related Side Note: While Missouri does not draw a “Route 16 like” line below which fall Nitrogen is not recommended. It does note that Route 16 would correspond roughly with Route 36 in Missouri. The University of Missouri advices extreme caution toward fall applications south of that area.
o Related Side Note: The University of Missouri states that Fall applied anhydrous (fall applied Nitrogen) should never account for more than half a grower’s nitrogen program (due to concerns that Fall dominated Nitrogen applications will equate to more N loss).
- Never apply Nitrogen to potential corn ground during the winter.
- Apply some spring nitrogen:
o Spring anhydrous should probably make up a portion of nitrogen applications in the “fall applied area” regardless of the state in question (the University of Missouri recommends using anhydrous if the period between nitrogen application and planting will be greater than two weeks).
o Missouri recommends that spring applications/post applications represent more than half of the nitrogen program.
o Missouri recommends an N stabilizer in spring applied anhydrous.
o Related Side Note: Wait 3 to 5 days to plant post-application. When applying pre-N, consider applying it at an angle to projected planting.
o Related Side Note: Urea should be spring applied not fall applied.
- Be sure to apply nitrogen at the correct depth:
o Anhydrous should be 8 to 10 inches deep in sandy soils
o Anhydrous should be 6 to 8 inches deep in loam soils
o Liquid N should be incorporated a couple to few inches deep
o Urea products should be incorporated (preferred – surface application on low residue ground with Agrotain would be a second best option).
- Consider rescue Nitrogen when spring rains saturate the soil for extended periods of time.
- Do not apply more than 60 pounds of 28 percent/32 percent with post herbicides (foliage may burn). Injection is the preferred application mode with dribbling a second best option.
- Practice good weed control (the fibrous root system of many weed species can rapidly take in nitrogen, rapidly depleting the crop’s available N supply).
(The Matt Montgomery)