Fall Fertilization Tips
Date of publication : 10/17/2008
Source : Govt of Alberta Agriculture and Rural Development
When it comes to fertilization, application at the time of seeding (seed-placed, sidebanded, or mid-row banded) is the most effective method of application while fall broadcast is the least effective.
"However, fall-banded N will be as effective as spring banded if there is no concern with wet, saturated soils in the spring," says Dr. Ross McKenzie, agronomy research scientist with Alberta Agriculture and Rural Development, Lethbridge. "In fact, fall-banded N may be more effective than spring banded when lack of seedbed moisture is a concern."
If soils tend to be saturated with water for extended periods in the spring, then fall application is probably not a good option. However, if saturated soil conditions are normally not a problem, fall banding should work well.
Soil test to determine the optimum rates of fertilizer required. "We encourage producers to sample 0 to 6, 6 to 12, and 12 to 24 inches to determine the cumulative N to 2 feet," says McKenzie. "Apply a conservative rate, say 75 per cent of soil test recommendation, or 75 per cent of what you would expect to apply next spring, or if you haven't got your soil test results back at time of application. This conservative fall rate is a hedge against such things as high soil test N levels, low spring moisture or low crop prices. If conditions look favorable come spring, additional N can be applied at the time of seeding.
However, the amount of additional N that can be drilled with small seeded crops like canola is only 10 pounds per acre with a disk drill (10 per cent seedbed utilization) and up to 20 to 35 pounds per acre with an air seeder, depending on seedbed utilization."
Select a fertilizer formulation that is right for the conditions. "Generally under low risk conditions, such as in southern Alberta, anhydrous ammonia (82-0-0), urea (46-0-0), or liquid nitrogen (28-0-0) perform equally well when fall banded," says McKenzie. "However, soils in southern Alberta tend to be alkaline (higher pH), and losses through ammonia volatilization can occur if the bands are too shallow or the soil is dry and cloddy."
Avoid the use of the nitrate-containing products such as 28-0-0 on soils that tend to be saturated in the spring. Nitrates are subject to both denitrification and leaching losses under wet spring conditions.
"Apply N in late fall after the soil temperature has dropped below 7øC and the nitrification process has slowed down," says McKenzie. "And band, don't broadcast. Banding restricts the contact between soil and fertilizer, and as a result, losses over winter are lower."
Other management factors:
* Fall fertilization can improve your time management. By applying fall fertilizer, a field operation can
be eliminated in the spring, which can allow earlier planting.
* Fertilizer prices and payment schedules tend to be more favorable in the fall, making it economical
to fall apply.
* Availability of product and application equipment is often better in the fall than during the peak
demand periods in spring.
* Soils tend to be drier in the fall, so N application equipment is less likely to cause soil compaction.
"As you can see, there are a number of agronomic factors to consider before you go ahead and fall apply N," says McKenzie. "You may want to consult with a soil fertility specialist while you're setting up your fall fertilizer program. It is always a good idea to get several opinions and consider all the factors before you make your final decision."
By Dr. Ross McKenzie
Agri-News - Government of Alberta Agriculture and Rural Development
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