Battle for the Belt: Season 2 Episode 12- Nitrogen Recommendations for Corn

Episode 12 of Battle for the Belt is now available: https://www.youtube.com/watch?v=Y2kzyppty88

In Episode 12, we discuss nitrogen management in corn with Dr. Manbir Rakkar, the Ohio State Soil Fertility and Nutrient Management Specialist.

What is the optimal rate for sidedress nitrogen application in Ohio?

The optimal rate is the amount of nitrogen that will give us the maximum net profit. Nitrogen is a major essential nutrient but the relationship between corn yield and nitrogen input is not always linear. When we add nitrogen, the very first units of nitrogen are what gives the largest yield increase. The yield response of corn to nitrogen application generally will plateau and decline after a certain point. Another factor to consider is the cost of nitrogen and the price of corn.

There is a tool that considers all these factors, yield response, cost of nitrogen, and corn price, called the Maximum Return to Nitrogen or MRTN. You can find the tool at https://www.cornnratecalc.org/. To use this tool, enter your location, the crop rotation (corn after corn or corn after soybean), the source of N (UAN, anhydrous ammonia, urea, etc), the nitrogen product price, and the corn price per bushel. The tool will then calculate the recommended N rate for your specific situation. The tool is informed by intensive research conducted across Ohio and several other corn belt states and is continually updated.

At what stage should we sidedress corn?

The recommended stage of sidedress application in corn is the V4/V5 stage. Corn only uptakes about a pound of nitrogen from planting to V4. After V4 through tasseling the corn dramatically increases (Figure 3). The target for sidedress application is to apply nutrients with crop needs.

I missed my sidedress application timing, what do I do?

Even if the weather did not permit a sidedress application at the V4/V5 stage, this application is necessary for yield, and crop uptake is at a high from the V4 to tasseling. So, any time that you have the ability to get into the field to make the application that will be agronomically and economically practical.

How do we identify a nitrogen deficiency?

Nitrogen deficiencies are characterized by chlorosis of the leaf in a V shape beginning at the tip of the leaf and moving down the midrib toward the leaf base (Figure 4). Nitrogen is mobile in the plant so this deficiency will be seen in the lower leaves because the plant will use the older leaves to supply new leaves with nitrogen.

What are more resources for fertility recommendations in Ohio?

For more information and Ohio fertility recommendations including phosphorus, potassium, lime, and micronutrient recommendations for our main crops consult The Tri-State Fertility Guide. A physical copy of the book can be purchased or a free pdf can be downloaded.

Another option is the Ohio Agronomy Guide which has cultural management practice recommendations for corn, soybean, wheat, and alfalfa.

What’s happening in the field?

In the field this week, the ultra-early planted (3/25) soybeans at the Western location began to show pods and the second planting date (4/16) was at full flowering (R2). Both planting dates have had early flower dates and will be interesting to follow the rest of the season. For both crops, there is no sign of disease.

At the Northwest location, planting date three was put in the ground on June 10^th. This area of Ohio has progressed in planting in the last week.

At the Wooster location, there has not been significant disease pressure in either crop but a presence of Septoria brown spot in soybean and anthracnose in the corn. Neither of these diseases should affect yield.

A summary of weekly conditions for all three sites and completed planting dates is presented in Table 2.