By Cheryl Manness
One of the most challenging factors for producers when planting winter wheat is nitrogen (N) fertility. According to Fertilizer Canada, the 4R Nutrient Stewardship approach, Right Source @ Right Rate, Right Time, Right Place, can be helpful in enhancing production and profitability while protecting the environment and improving sustainability.
Using the 4R approach begins with understanding soil fertility and selecting the right source to ensure the soil has a balanced supply of essential plant nutrients. Every field is different when it comes to nutrient contents in the soil and can vary from year to year, so it is essential to perform soil sampling and testing prior to planting any new crop.
Applying nutrients at the right time will ensure nutrient uptake when the demand is high and applying them in the right place helps minimize the risk of loss while increasing availability of nutrients to the crop.
A four-year research study conducted in southern Alberta in the brown, dark brown, and thin black soil zones, concluded that nitrogen fertilizer can be successfully applied in the fall. The study found that reduced winter hardiness, reduced plant populations, or reduced yield were not observed with increasing rates of fall applied N fertilizer, but when seeding winter wheat in stubble fields low in soil N, the N fertilizer improved stand establishment and overwintering ability. Nitrogen applied at the time of seeding was generally as effective and often more effective than spring broadcast nitrogen.
Research data examined and published by Westco Agronomy states there are a number of advantages for farmers to be able to apply all of the N requirements for their winter wheat crops at planting time, including more favourable nitrogen pricing, ability to use a less expensive nitrogen format, reduced application costs, mitigation against wet spring conditions, and maximized yield potential.
Early spring N is extremely important to the crop’s final yield. Fall applications help ensure N is available as wet spring fields often make it difficult to apply N on a timely basis.
Possible disadvantages of N applications at seeding time are the risk of seedling damage and the risk of significant N losses. Seedling damage can be overcome with openers, which place fertilizer away from the seed row. The risk of N losses due to denitrification or leaching can be substantial if warm, moist soil conditions persist for a long period following seeding. The use of slow release N products can mitigate some of the challenges associated with unpredictable weather.
Topdressing with urea in the late fall, usually at temperatures below 100 Celsius has gained attention. At temperatures this low, N losses are usually minimal; however, precipitation, as wet snow or rain within a five- to seven-day window, is required to move the fertilizer into the soil so it does not volatize. If temperatures are warmer, 150 Celsius, a rain within a day or two of application is necessary or losses will occur.
Another option is to split the N fertilizer application between the fall and spring. This option may be a good choice for growers who want to ensure their crop has enough N to make it through the first few weeks of growth in the spring until they can get out and top dress the balance. The remaining N requirement based on soil moisture and crop conditions would be applied in the spring.
Choosing the right source/lowest risk product based on best management practices may help reduce risks associated with broadcasting if this is the best choice to achieve the desired nutrients to the crop at the right time and right rate.
Regardless of the option chosen, it is critical to use adequate rates to support the growth requirements of the crop.
To learn more about 4R Nutrient Stewardship practices go to the Fertilizer Canada website at Farming4RFuture.ca.