Posted August 31, 2017 

In Western Canada, our growing seasons are short. Applying NH3 post-harvest has a few distinct advantages including lower fertilizer prices, greater equipment availability and a workload that is spread more evenly throughout the year, allowing more time for seeding in the spring.

Surveys have shown a clear link between high-yielding crops and fall fertilizer application. This is often related to earlier seeding times and better seedbed quality. Properly applied, fall fertilizer is generally equal in effectiveness to a spring application. Fall banding is generally better than spring broadcasting and very comparable to spring banding.

Getting optimum results

Generally the concern with fall-applied nitrogen (N) is that it will be lost before the crop gets to it next spring. The following guidelines are recommended for optimum performance in annual crops:

Use ammonium fertilizers – either ammonia or urea

These preferred sources best resist loss. Since liquid N contains about 25% nitrate nitrogen, it is slightly more vulnerable to losses.

Band the fertilizer

Concentrating the fertilizer in bands slows down the rate that soil microbes convert nitrogen into a form that could be lost in the spring. Banding 3-5 inches deep with shank spacings of 10-16 inches is recommended. If using ammonia, ensure soil flow around the shanks is adequate to retain the ammonia. Soil that appears quite dry will still hold ammonia as long as there is good movement of soil around the shanks.

Soil test to determine how much fertilizer is needed

Depending on the region, soils are often cool enough (below 10 degrees Celcius) to begin fall banding by late September. The cooler the better, but you do run the risk of waiting too long and being caught by freeze-up. Fall sampling can start immediately after harvest and no major changes in nutrient levels are expected. Soil test values can be influenced to varying degrees by precipitation, organic matter, nutrient levels and previous crop. 

Don’t delay 

There is a perception that there is a high risk to N lost when fertilizer is applied in the fall.  A number of research studies have shown that we can apply N fertilizer much earlier that what is conventionally thought, at temperatures below 10 degrees Celcius. (See figure 1.)

Start on well drained land

Start banding the fields that are well drained or prone to drying out. These soils will benefit the most from fall banding and there is a reduced risk of N loss in these fields. In addition, these soils suffer the most from spring tillage operations. Leave the poorly drained land until last. Land that ponds in spring is more susceptible to N losses. Delaying fall banding in these situations allows the soil to cool more, which helps preserve the nitrogen. (See figure 2.)

Nutrien Ag Solutions supplies growers with NH3 from many of our locations, primarily in the northern Prairies. For NH3 to be a good choice of crop nutrition for a farm, it needs to fit within the parameters of 4R Nutrient Stewardship agronomy – the Right fertilizer applied at the Right rate, at the Right time and at the Right place in the soil.

Talk to your local Nutrien Ag Solutions retail for help with soil sampling and which fall fertilization options will work best for your farm. 

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Posted September 01, 2017