It is not too late to finetune nitrogen rates for your corn fields!
Nitrogen rates are a moving target with many factors contributing to what the most economical rate for each field is. Nitrogen is mobile in the soil and influenced by weather more than the other macro nutrients like phosphorus and potassium. Other factors, like crop rotation, manure, and soil type, can also influence the ideal rate that should be applied to each field. With many different methods to apply nitrogen in season, even if your corn is already planted, you can still finetune the nitrogen rate for the need of your crop.
Corn is very responsive to nitrogen, and making sure we have adequate supply throughout the growing season will help maximize your yield. However, excess nitrogen can be lost, is negative for the environment, and lowers your return on investment. A tool that Maizex uses to help estimate appropriate nitrogen rates is the Maizex N Tracker. The N Tracker is based on the Ontario N Calculator, with some modifications that have been made based on additional research and field experience. It helps you to take into consideration many of the variables on your specific field and provides a tailored recommendation.
Below are three examples of fields with different rotations and manure applications and how the recommendations change for each. You will notice that giving the correct credit for the previous crop and for manure applications can have a huge impact on the N rate recommendation. Notice also that, in many situations, there is some efficiency gained by applying nitrogen in the sidedress window; that is, total N rates are lowered when N is applied in the sidedress window compared to the planting window.
For additional N rate inquiries, be sure to check out the 2021 version of the Maizex N Tracker.
Scenario A. A 2750CHU area with loam soil. The previous crop was grain corn, and the planter had 11 pounds of nitrogen in the starter at planting. The producer applied 5000 gal/ac of liquid dairy manure this spring (an N credit of 83 lbs/ac). This scenario requires an additional 109 lbs/ac of nitrogen at planting timing.
Scenario B. A 2750 CHU area with loam soil. Previous crop was alfalfa, and the producer applied 5000 gal/ac of liquid dairy manure this spring (an N credit of 83 lbs/ac). The planter had 11 pounds of nitrogen in the starter fertilizer. This scenario does not require any further nitrogen according to the N Tracker.
Scenario C. A 2750 CHU area with loam soil. Previous crop was wheat with the straw removed, and the producer applied 15 MT/ac of solid dairy manure this spring (an N credit of 66 lbs/ac). The planter had 11 pounds of nitrogen in the starter fertilizer. Recommended 100 lbs/ac additional nitrogen rate at planting.
Manure Credits. The above scenarios used manure credits calculated with the OMAFRA manure values from the tables seen below. Please see the OMAFRA Factsheet for other sources of manure that you may use on your farm and the average nutrient composition they may have.
Note: Multiply the Usable N1 by your application rate to determine your manure credit.
Liquid Dairy Manure
Solid Dairy Manure