In 2004 we had 30" of rain in June. This year it was not as much rain but the rain has been nearly constant and has kept our soils saturated for a very long time. I have contacted Carrie Laboski, U. W. Professor & Extension Soil Scientist and Joe Laurer, U.W. Corn Specialist about their thoughts on what should be considered. Below are their comments.
Basic understanding and reminder of the action of nitrogen in the soil.
Remember when you put on the nitrogen it is in the NH ??ammonia form and is converted by the microbes in warm soil to Nitrate N0 ??. The soil colloid is negatively charged so the ammonia is held by the soil but once converted to nitrate, the nitrogen can be loss to denitrification (as a gas to the attmosphere) and can be leached below the roots. With that said, take a look at the U.W. experts thoughts on what to do.
Joe Lauer, July 7, 2014
At nearly all of our sites we have added 40 to 80 lb N/A. The corn plant will continue to take up N until flowering and then continue uptake until the milk stage but at a slower rate. So it might be reasonable to help the corn plant along by adding some N in fields that appear stressed. It is difficult to determine where the N is in the soil profile. By adding a little it might help the plant to "find" the N deeper in the soil profile. Remember corn roots can grow 3 feet to the side and 5-7 feet into the profile.
Carrie Laboski, July 7, 2014
I suggest 50 lb N/a to apply. But if more than 100 lb N/a may have been lost, then consider applying ~ 50% of the N that was lost. Your current situation is a bit challenging in that the soils have remained wet and there has probably been some amount of physiological damage to the crop from lack of oxygen to the roots. Thus, it is really hard to know how much N to apply for a maximum economic response, because it's more than just N loss, it's crop damage.
Joe Lauer, July 7, 2014
Greg's Question What about planting something else in the worst fields with large areas of flooded conditions?
So considering the need for dairy feed and the cost N. I would apply 50 lb N/a, maybe a little more if you wanted. I would not tear out the corn and plant an annual forage. You'll likely get more biomass from this corn crop than something else that isn't planted until mid-July. Consider that soils might dry out enough this week to get on the field, but will the dry soils last long enough to kill the corn, do some tillage (?) and plant another crop before it rains again? That is a risk. Also consider that alfalfa doesn't like wet feet and this might not be the best situation to start a hay crop, and the amount of biomass produced yet this season may not be all that high.
Conclusion
With the cost of nitrogen at $0.42/unit of N plus application cost, it would cost around $33.00/acre to put on 65 units of nitrogen. At $3.85/bu. of corn you would need a yield increase under a 10 bu./acre response to break even. My thought would be to cultivate these fields to get some oxygen into the soil and apply the suggested amount of nitrogen. I suspect cultivating some fields or areas within fields would be all that is needed.
Just over the last 24 hours I have seen the corn really start to green up with the drier weather. Getting another 1 ½ inches of rain last night at Oakfield wasn't a help.
Corn field condition notice
Greg Booher
Lakeshore Technical College
Farm Business Instructor
7.8.2014