A recent Ohio State University on-farm trial compared the impact of 2 sidedress nitrogen rates on the yield response of strip-till corn following a rye cover crop.
During the prior fall, on 10/22/22, a cereal rye cover crop was planted in twin rows at a rate of 50 lbs/A after soybean harvest. Fall fertilizer was applied at 97 lbs/A of DAP (18-46-0), 40 lbs/A of AMS (21-0-0-24S), and 3 lbs/A of Boron via strip-till.
Nitrogen fertilizer at two rates was applied to the corn trial at sidedress. Each treatment was replicated three times in a random complete block design. Each replicated plot was 40 feet wide by 700 feet long. All plots received the same inputs except for the sidedress N application rates. Sidedress application was at V6 stage (6 collared leaves) and Treatments 1 and 2 were 110 lbs/A and 162 lbs/A of 28% UAN, respectively. Yield and grain moisture were obtained by a calibrated yield monitor. Yields were adjusted to 15.5% moisture. A simple economic analysis was conducted using the adjusted yield and the values of $4.50/bu for corn and $560/ton UAN N ($3.00/gal).
The trial resulted in a significant difference in yield response to the varied nitrogen rates. A rate of 54 gallons of 28% UAN per acre led to an increase of an average of 5.1 bushels per acre compared to a rate of 37 gallons of 28% UAN per acre. However, the higher rate of nitrogen incurred a relative loss of $28.05 per acre since the value of the increased corn yield did not make up for the additional cost of the additional nitrogen. Yield and the cost of inputs made the 37 gallons of 28% UAN per acre treatment the more economical practice. The maximum return to N rate is calculated to be between the two treatments, so a slight increase in N from treatment 1 may have resulted in a yield response sufficient to offset and surpass the cost of additional N.
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Summary
The rate of nitrogen applied can impact the yield response of a corn crop, as seen in this trial. This trial highlighted the importance of an economic analysis to verify that a determined nitrogen rate is a sound farm decision for producers. The variety of farming practices, the fluctuation of input prices, and the regional diversity of agricultural land provide numerous options for continued research, to provide sound, applicable, and regional information for local farming operations. To build off this research, future work can be conducted assessing a greater number of N rates, the impact of split applications, and the interaction between N rate and management strategies like cover crops and application methods.
