FERTILIZATION OF SPRING CANOLA
A soil test is highly recommended in the spring. A good soil test will eliminate guessing on soil nutrient test levels and will easily pay for themselves in fertilizer savings or better crop yields. A top soil to 10-12" and a subsoil sample of 10-20" is recommended.
NITROGEN
Total Nitrogen Requirement = 0.06 x Yield Goal in Lbs./Acre
In the San Luis Valley this will equal 170-190 Lbs./A Nitrogen. Don't use more than 200 for this total.
In other areas with a lower yield goal the nitrogen requirement will be lower. A realistic yield goal is necessary for this formula to work well for your farm.
Use a Nitrogen budget and soil test results to determine what the actual field will need:
Nitrogen requirement: ___________________________
Surface soil Nitrate-N: _____________________________
Subsoil Nitrate-N /2 : _____________________________
Organic Matter N Release: _________________________
Manure N Release: _______________________________
Irrigation Water Nitrate: ___________________________
NITROGEN FERTILIZER REQUIRED:_______________ (Lbs./A)
(Subtract the various nitrogen forms available from the nitrogen requirement to get the nitrogen required)
Organic matter release in the SLV = 10 x % Organic Matter in topsoil which is usually 10 units nitrogen/A.
In Warmer areas the O.M. release will be 20 x O.M.% or even 30 x O.M. %.
Irrigation well water supplies some nitrogen, but varies with location and depth of well. Use the following table to interpret water test results to estimate the nitrogen supplied by the irrigation well water.
|
Nitrogen Credit from Irrigation Water | |||||
| No3N-N in Water | Water Applied (inches) | ||||
| ppm | 6 | 12 | 18 | 24 | 30 |
| 1 | 1 | 2 | 4 | 5 | 7 |
| 2 | 3 | 5 | 8 | 11 | 14 |
| 3 | 4 | 8 | 12 | 16 | 20 |
| 4 | 5 | 11 | 16 | 22 | 27 |
| 5 | 7 | 14 | 20 | 27 | 34 |
| 6 | 8 | 16 | 24 | 32 | 41 |
| 7 | 9 | 19 | 28 | 38 | 47 |
| 8 | 11 | 22 | 32 | 43 | 54 |
| 9 | 12 | 24 | 36 | 49 | 61 |
| 10 | 13 | 27 | 40 | 54 | 67 |
| 12 | 16 | 30 | 45 | 60 | 75 |
| 14 | 19 | 38 | 57 | 76 | 95 |
| 16 | 22 | 43 | 65 | 86 | 108 |
| 18 | 23 | 49 | 73 | 97 | 122 |
| 20 | 27 | 54 | 81 | 108 | 135 |
Calculating release of nutrients from manures is always tricky and is best done with experience and a nutrient test of the manure to be used. Soil temperature can influence release as well from year to year. Use the table below to estimate nutrient content on a dry basis of various manures.
| Manure | Total N | Ammonium N | Phosphorus | Potassium | Sulfur |
|
Lbs./Ton | |||||
| Non-Composted Poultry | |||||
| Turkey | 35 | 4 | 53 | 37 | 6 |
| Fresh Broiler | 78 | 6 | 51 | 53 | 9 |
| Fresh Layer | 79 | 8 | 125 | 67 | 16 |
| Aged Layer | 43 | 9 | 164 | 79 | 14 |
| Non-Composted Dairy/Steer | |||||
| Fresh Dairy separator solids | 43 | 1 | 17 | 12 | 10 |
| Fresh Dairy corral scrapings | 47 | 2 | 26 | 141 | 12 |
| Aged Dairy separator solids | 41 | 1 | 13 | 8 | 9 |
| Aged Dairy corral scrapings | 26 | 5 | 31 | 66 | 8 |
| Composts | |||||
| Broiler | 38 | 2 | 86 | 50 | 11 |
| Dairy | 27 | 1 | 27 | 57 | 9 |
| Dairy/Steer | 33 | 0 | 17 | 51 | 9 |
| Dairy/Poultry | 34 | 2 | 39 | 75 | 29 |
If you don't have soil sample results the top and subsoil nitrogen residual can be estimated:
After a wet winter you'll want to subtract 20 - 30 units from these amounts and after a dry winter you'll want to add 20 - 30 units nitrogen to these residual amounts.
Nitrogen Timing: Canola responds to splitting nitrogen applications. Applying 10 - 30% of nitrogen fertilizer required just as flower buds appear can improve yields. The remaining should be applied preplant or at planting with any needed phosphorus, potassium or sulfur fertilizer. The timing for any injected nitrogen is also a good time to apply any needed Boron fertilizer.
Nitrogen and water. If the canola crop is water short such as in a dryland crop, water will be the limiting requirement and extra nitrogen will not increase yields. Under a water rich field early season adequate nitrogen is key to high yields. Again, use a realistic yield goal in these calculations.
Use a soil sufficiency method to determine any needed phosphorus:
| Mehlich test results
ppm |
Olsen Sodium Bicarbonate results
ppm |
Phosphate Requirement in Lbs./A P2O5 |
| Above 70 | Above 35 | None needed |
| 50 - 70 | 26 - 32 | 25 Lbs./A |
| 40 - 50 | 21 - 26 | 40 Lbs./A |
| 30 - 40 | 15 - 21 | 60 Lbs./A |
| 20 - 30 | 10 - 15 | 80 Lbs./A |
| 10 - 20 | 5 - 10 | 100 Lbs./A |
Phosphorus availability varies a lot in SLV soils. Adjustments should be made to these recommendations.
If you don't have soil test results fields with a good history of potatoes will need 0-25 Lbs./A phosphorus and grain on grain situations it can vary from 40 - 80 Lbs./A.
Potassium
Most western soils have sufficient potassium levels for a canola crops but some areas may need some additional potash applied. Use the following table to determine amounts needed:
| K test value in ppm | less than 50 | 50-150 | 150-250 | 250-350 | 350- |
| K needed in Units./A | 100 | 50 | 40 | 20 | 0 |
Sulfur
Canola is a heavy user of sulfur which is a mobile nutrient like nitrogen which can move with soil water. Sulfur availability should be 1 unit of sulfur to 4 units nitrogen, but apply at least 40 units/A sulfur at a minimum.
Micronutrients
Boron: In many western areas of the U.S., the irrigation water should contain enough boron for a good canola crop. Boron is a mobile nutrient and will move with soil water. Applications 0.5 to 1 Lb./A boron may boost yields in these areas. This is best injected at the start of blooming. There are commercial blends with boron or use 10% boric acid.
Studies to date on Canola have shown no yield response to any other micronutrient other than Boron. No other micronutrient should be needed on the canola crop.
Note: This information should only be used as a guide. Adjustments for local conditions must always be made.