The agriculturally troubled fall of 2009 may be over, but here comes the sequel — a potentially wet spring.
Normally corn residue is thought of positively because it lowers the risk of erosion and returns carbon and nutrients to the soil. However, it’s not very friendly getting it through planting equipment in the spring, says Dan Kaiser, soil and plant nutrient specialist for the University of Minnesota.
Kaiser offers some answers to a couple of pressing questions that many growers are asking after a difficult harvest, abundant moisture and much corn residue:
Should I apply nitrogen to help break down corn residue?
"It sounds good in theory, but no field research in our region shows increased breakdown of residues from additional nitrogen," Kaiser says. "The breakdown of residues slows during the winter. The activity of organisms is dictated by soil temperature, so additional nitrogen in the spring will not affect the rate of decomposition early in the season if cool and wet conditions persist."
Kaiser says baling residue would have been a better strategy for fall then spring, but chopping residue could help break residue into smaller parts to go through planting equipment.
"While it's not ideal, burning residue may alleviate problems for spring," he says. "No matter what is done, make sure that the planter is equipped with row cleaners that are in good working order, especially in continuous corn where you’ll want clear rows for stand establishment."
What should I do for my fertilizer application in a wet spring?
Wet soils can cause significant problems with fertilizer application, Kaiser says. Nitrogen fertilizer sources are susceptible to gaseous losses, he says, adding poor application depth of anhydrous ammonia and surface application of urea with no or shallow incorporation can lead to losses of ammonia gas.
"Apply anhydrous ammonia to a depth of at least 4 inches," Kaiser says. "Incorporate urea as soon as possible after application, if no rainfall is expected, at a depth of at least 2 inches. If fertilizer cannot be incorporated, products like Agrotain can be used to lengthen the time between application and incorporation."
For anhydrous ammonia, Kaiser recommends making sure slits in the soil are properly sealed behind the knives and ammonia is not being lost.
"Try to avoid direct application of urea ammonium nitrate solutions to crop residue to lessen the risk that it may be tied up in microbes when the residue is being decomposed," he adds.
Since time in the spring is limited, he urges producers to take care when applying fertilizers for the 2010 crop. While fertilizer prices have decreased in the past year, he says it's still is a significant investment, and protecting that investment should be a top priority.
Kaiser offers a couple relevant publications for additional information: