Canola is a nitrogen-intensive crop and nitrogen (N) management is a key factor to consider for successful production. Researchers at K-State University and Canola Council of Canada stated that canola requires 2.5–3.5 lb/ac available nitrogen (N) per bushel of seed produced. Ensuring sufficient N availability is crucial for achieving competitive yields. In AGR-1, the Lime and Fertilizer Guide for Kentucky, N recommendations include no more than 30 lb N/acre in the fall and up to 120 lb N/acre in February and March for Canola following corn, soybeans, small grains or fallow land. If Canola is following a perennial sod or legume, then the total nitrogen can be reduced to 90 lb N/acre. 

Recent research in Kansas, on different soils and in a drier climate, follows a different nitrogen guideline. Because several Canola resources reference this method, we are going to explain that method here. This method uses a yield goal approach, and factors soil organic matter (SOM) into the equation. 

In soil with 2% organic matter, Kansas State research suggests applying at least 2.5 lb of N/acre per expected bushel of canola using the following formula:

Soil organic matter (SOM) influences N availability and should be considered when determining N application rates. If the SOM is 3%, 15 lb less N/acre should be applied, whereas if the SOM is only 1%, increasing the N rate by 15 lb is beneficial. 

For example, if the expected yield target is 60 bushels/ acre in soil with 2% organic matter, the total N requirement is 150 lb N per acre. If SOM is 3%, then 135 lb N/acre is suggested. In this system, the farmer would apply up to 30 lb N/acre in the fall, 52.5 lb N/acre in February and 52.5 lb N/acre in March. For the example of 150 lb N/acre as a total application, the schedule would be 30 lb N/acre in fall, 60 lb N/acre in winter, and 60 lb N/acre in spring. (Note: These total N rate recommendations, based on calculations, end up very near the range suggested by the University of Kentucky.) Since N application is split between fall, winter, and spring, farmers should always subtract soil N from the fall application amount to avoid excessive early growth. For example, if the total N requirement is 150 lb/acre and the soil nitrate test from 1-foot soil cores shows 20 lb N/acre (10 ppm N), then only 130 lb N needs to be applied through fertilization. 

Early-planted canola requires only a small portion of its total N in the fall as suggested earlier— typically one-third to one-fourth of the total N requirement—since it has sufficient time for growth before winter. Applying excessive N in the fall can lead to excessive vegetative growth, reducing winter survivability. On the other hand, later-planted canola should receive a higher fall N application— up to 40% of the total N requirement—to promote rapid growth and ensure plants reach the rosette stage before winter dormancy. Therefore, a balanced N distribution ensures optimal crop development and maximizes yield potential. 

While growers use various sources of N fertilizer, such as chicken or poultry litter (which contains 34 -72 lb N per ton), caution is necessary to avoid over-application. For example, applying two tons of chicken litter could supply over half of canola’s total N needs, potentially leading to winter kill. Nevertheless, the N mineralization rate in chicken/poultry litter varies due to factors such as weather conditions, application methods, and soil properties. Therefore, exercise due diligence and consult with your extension agent or your supplier to understand the nutrient availability and appropriate application strategies for chicken or poultry litter.

For chemical fertilizers, ammoniated phosphorus sources, such as and DAP (18-46-0, commonly sold in Kentucky) and MAP (11-52-0, sold in Kentucky to a lesser extent), provide N without causing damage to small seeds and seedlings. N supplied through MAP and DAP should be considered as part of the total N. Furthermore, Kansas State University often observed yield increases to fertilizer sulfur (S) applications. The climate and soils in Kansas are very different than the soils in Kentucky. During winter and spring, Kansas State recommends applying N fertilizers in combination with S. They calculate 20 lb of S per one seventh of total N. For winter application, fertilizers like ammonium thiosulfate (21-0-0-26) or ammonium sulfate (12-0-0-24) provide both N and S, helping to support canola growth. In spring, avoid topdressing ammonium thiosulfate directly on tissues. Regardless of the specific product, the total amount of S should be applied in winter and spring, as fall application of S offers little benefit for canola. 

As winter application time approaches, farmers should be aware of the possibility of freezing temperatures in mid-February. Winter N applications are recommended when the average temperature exceeds 40°F. Winter N application ensures that N is readily available for the plant’s bolting process. 

Before applying N, it is highly recommended to monitor your canola closely and seek expert advice. Start by assessing whether your canola has survived the winter. Look for green leaves at the growing point and feel the growing point with your fingers. A fleshy growing point indicates a dead plant, whereas a firm growing point suggests the plant is still alive. 

An extreme lower limit for plant survival is two plants per square foot. If you find that your canola won’t meet this threshold, applying N may be a waste of money, and it might be best to consider switching to another crop.

The spring N application should be made about one month after the winter application, but it should be timed early enough to avoid delaying canola flowering and maturity. A delayed application could delay maturity, which would in turn push back soybean planting. 

Acknowledgement: We'd like to thank Dr. Edwin L. Ritchey, Extension Associate Professor, for reviewing the content of this article. 

Reference: 

Bushong, J., Lofton, J., Sanders, H., & Stamm, M. (2018). Great Plains canola production handbook. K-State Research and Extension. 

Canola Council of Canada. (n.d.). Nitrogen. Canola Encyclopedia. Retrieved [02/10/2025], from https://www.canolacouncil.org/canola-encyclopedia/fertility/nitrogen/  

Chastian, J.,P., Camberato, J.,J., and Skewes, P. (n.d). Poultry Manure Production and Nutrient Content (Chapter 3b). Retrieved [02/10/2025], from https://www.clemson.edu/extension/camm/manuals/poultry/pch3b_00.pdf   

University of Kentucky Cooperative Extension. (n.d.). AGR-1: Lime and nutrient recommendations. University of Kentucky. Retrieved [date], from https://publications.ca.uky.edu/sites/publications.ca.uky.edu/files/AGR1.pdf  

Optional Citation: Shamim, M.J., Lee, C., 2025. Nitrogen Management Strategies in Winter Canola. Kentucky Field Crops News, Vol 1, Issue 2. University of Kentucky, February 14, 2025.