When it was time to snap the shutter on the camera and take a farm family picture, your corn was not smiling last year. In fact it may have been frowning when 1,500 aerial photos were taken of Midwestern cornfields to help evaluate if they were starved for nitrogen. Were they?
Yes they were, says University of Missouri agronomist Peter Scharf, who says his collection of aerial photos and the 2,000 miles he drove to inspect Midwest cornfields, prove that nitrogen loss was one of the challenges due to high seasonal rainfall. His March newsletter lays out his contention that a substantial part of the 2009 corn yield was not realized due to widespread nitrogen deficiency. He says visual surveys, followed by aerial surveys in August causes him to estimate that MO lost 100 million bushels of corn, and compared to the 438 million bushel crop, he says that would be a 20% yield reduction. But that is not all.
Scharf says he drove 2000 miles through Missouri, Arkansas, Kentucky, and Tennessee, as well as most of Illinois, southern Indiana and eastern Kansas. That was an area which had a minimum of 16 inches of rain from April to June, and he concluded it was detrimental to the supply of nitrogen available to the corn.
1) A 20 bushel per acre yield loss on average in Illinois, costing 150 million bu.
2) A 15 bushel yield loss in Indiana in the affected area.
3) An estimated 500 million bushel total loss in IL, MO, IN, IA, KS, KY, AR & TN.
4) That loss followed a 500 million bushel Midwestern loss in 2008 from N loss.
The loss of N meant a loss of $. Scharf says MO economist Ray Massey calculated the loss of 20 bushels per acre of pure profit.
Scharf says his preference is anhydrous ammonia as a nitrogen supply because it is the slowest to convert to nitrate in the soil, and sidedress application is “virtually loss-proof.” For preplant, he also suggests anhydrous ammonia, but he says it did not deliver enough N in either 2008 or 2009. He is an advocate of a rescue treatment of nitrogen if earlier applications have been lost due to wet weather. His newsletter provides some anecdotal evidence of those types of treatment, showing it is not too late to apply nitrogen when deficiency symptoms are visible. He says the logistics of getting the N applied is a greater obstacle than the ability of the crop to use it. He suggests high clearance applicators, pivot irrigation and airplanes can apply N to stressed corn.
One of the problems he identifies is the lack of sprayers that have drop nozzles between the rows, an issue that can be solved by every commercial applicator. And he says now is the time for those applicators and farmers to develop a plan for a rescue treatment should it be needed. Other alternatives for nitrogen rescue treatments include:
1) Broadcast applications of dry N when leaves were dry burned the corn but the yield was only 4 bushels less than with drop nozzles.
2) Agrotain treatment of urea gave a profitable yield response when broadcast on corn that was up to two feet tall, but not when corn was three and four feet tall.
3) Ammonium nitrate burn reduced yield about 20 bushels per acre when broadcast on three and four foot tall corn.
4) UAN solutions caused losses of up to 70 bushels per acre, and should only be applied with drop nozzles between rows.
How do you know if your corn has a nitrogen deficiency? Scharf says appearance is a good indicator, but water logged corn may not be N deficient. He says waiting for the soil to dry out and for the corn to green up does waste valuable time for application of a rescue treatment. His top choice is aerial photos that identify problem areas and their severity of N shortage. He says they can be translated into yield loss maps, which make it easier to determine how much nitrogen is needed for variable rate applications.
Scharf also says deep soil samples can help, but the results are slow and the digging is labor intensive. Also computer models that integrate the weather data may work, but without the accuracy of field level observations.
Summary:
The wet weather of 2009 may have resulted in substantial corn yield losses for many Midwestern farms. Such losses may have been as much as 20% and were the result of lost nitrogen. When farmers determine there is a potential for nitrogen deficiency, rescue treatments should be implemented, but planning for those should be in the late winter and early spring.