Put nitrogen methods under microscope
Nitrogen got the blame when corn began turning quickly in early August. Expect nitrogen methods to go under the microscope.
This month’s Indiana Certified Crop Adviser panelists addressing N issues include Steve Gauck, Westport, Beck’s Hybrids; Willis Smith, Otterbein, Senesac Inc.; and Dave Taylor, Richmond, Harvest Land Co-op.
We planted early, but June rains hit us hard. I’m sure I lost N. How can I tell how much I lost, and if it affected yield? Is there a lesson to take into next year?
GAUCK: Rain this spring caused N loss everywhere. It didn’t seem to matter what type of N or the application method. By now it’s tough to tell how much N loss affected yield. For next year, evaluate your N program. Ask questions. Why did I use this program? What do I like about it? Split applications or sidedressing have the least amount of N loss, but timing is always a concern.
SMITH: Compare fields, areas and plants using a chlorophyll meter if you still can. Within the same field, find an area less affected by too much water and an area that shows the effects of N loss. Take a reading using the ear leaf. The two areas should have the same planting date, soil type, soil fertility levels and units of total N applied.
Next year, use the chlorophyll meter before it is too late to sidedress. Compare an area with sufficient N against others. Using this method may let you make N corrections soon enough to avoid yield loss.
TAYLOR: Early planting doesn’t equal N loss, but N application timing affects loss potential. If the bulk of N was applied at planting or preplant, loss could have been significant. There’s really no good way to estimate N loss. Visual properties of plants can tell us if we have N loss. Lower leaves that yellow to brown and vee in from margin to midrib are symptoms. The ear itself may be smaller with fewer kernels.
If you apply N at planting or before, protect with N-Serve. If you sidedress, apply some N at planting. Do not cut N rates below what’s recommended.
Should I give up on fall N applications?
TAYLOR: Giving up on a proven practice is difficult. Look deeper. If you need to increase N rates significantly to ensure good yields, give it up. If you feel N loss is great, give it up. If you do it, choose fields with good drainage, apply after soil temperature drops below 50 degrees F, use a nitrification inhibitor like N-Serve, and increase application rate 10% or so.
GAUCK: We are too far south. Timing is a factor, but you’ll have less N loss with spring applications. Anytime you apply N early, even in spring, use a nitrification inhibitor.
SMITH: If you believe in fall application, go ahead. Most suppliers will let you defer payment. Relative cost of N is usually less in the fall. If you do it, let soil temperatures cool and use an inhibitor.
I don’t believe in anhydrous, so I recommend ammonium sulfate with dry fertilizer at 150 to 250 pounds per acre, or 31 to 52 pounds actual N, plus 36 to 60 pounds of sulfur. The remainder comes from 28% applied with chemical, starter or sidedress.
This article published in the October, 2010 edition of INDIANA PRAIRIE FARMER.