by James W. Bauder

Canola is a significant crop of the Canadian Prairies and has been grown there for quite sometime. For many irrigators in the cooler parts of Montana, canola has become a significant cash crop in a very traditional cereal grain rotation. And, many producers are finding the benefits of a high yielding, high quality canola crop to be more than just economic. Canola disrupts disease cycles, creates opportunity to diversity herbicide use, and changes the timing of field operations.

The strong history of canola production on the Canadian Prairies makes our neighbors to the north a good source of information. The Irrigation Branch, Alberta Agriculture, Food, and Rural Development Department has a very thorough web site which you might visit if you want more information about canola variety selection, disease and weed management, and fertility guidelines. The address is: http://www.agric.gov.ab.ca/. Much of the information in this article comes from that web page.

Climate and Water Use
Canola performs well under rainfed conditions if the predominant weather condition is ‘cool' and seasonal rainfall and soil moisture average more than 15 inches. Note that this is seasonal moisture, not annual. Canola's success on the Canadian Prairies is partly due to the weather, the rainfall conditions, and the high water holding capacity of the soils.

The seasonal water requirement for canola depends on variety, target yield, and crop management. Canola consumes up to 20 inches of water during a growing season and will use as much as 0.3 inches per day during peak periods. That puts canola water use right in the range of most grain crops. Polish varieties tend to use less water than Argentine varieties; the Polish varieties generally are earlier maturing, which accounts for the decreased water use. In general, the earlier you can plant the crop, while still avoiding the potential of early frost damage, the less water it will use.

The most critical times for irrigating canola are during late vegetation/spiking and throughout the flowering period. Moisture stress during these periods can cause major yield reductions. In general, soil moisture levels should be maintained above 50% available moisture in the active root zone throughout the growing season. Canadian researchers report that the active root zone for canola is 48 inches. Because of the differences in capability of various irrigation systems or designs, slightly different strategies are proposed for different irrigation methods.

Center Pivots
Irrigation of canola can start as soon as seeding has been completed. Light, frequent water applications should be applied until the crop has fully emerged to avoid crusting. Once the crop reaches the vegetative stage, moisture levels should be increased to near field capacity. The point here is that once the crop develops to the point of pre-flowering, soil moisture should be kept at a level which will minimize stress. This will allow irrigators to avoid continuous irrigations during flowering and potential disease problems caused by wet soil surface conditions. Canola will use large amounts of moisture during flowering, and once an irrigator falls behind it is difficult to catch up. Pivot irrigators should continue to irrigate this crop until flowering is complete.

Climate and Water Use
Canola performs well under rainfed conditions if the predominant weather condition is ‘cool' and seasonal rainfall and soil moisture average more than 15 inches. Note that this is seasonal moisture, not annual. Canola's success on the Canadian Prairies is partly due to the weather, the rainfall conditions, and the high water holding capacity of the soils.

The seasonal water requirement for canola depends on variety, target yield, and crop management. Canola consumes up to 20 inches of water during a growing season and will use as much as 0.3 inches per day during peak periods. That puts canola water use right in the range of most grain crops. Polish varieties tend to use less water than Argentine varieties; the Polish varieties generally are earlier maturing, which accounts for the decreased water use. In general, the earlier you can plant the crop, while still avoiding the potential of early frost damage, the less water it will use.

The most critical times for irrigating canola are during late vegetation/spiking and throughout the flowering period. Moisture stress during these periods can cause major yield reductions. In general, soil moisture levels should be maintained above 50% available moisture in the active root zone throughout the growing season. Canadian researchers report that the active root zone for canola is 48 inches. Because of the differences in capability of various irrigation systems or designs, slightly different strategies are proposed for different irrigation methods.

Center Pivots
Irrigation of canola can start as soon as seeding has been completed. Light, frequent water applications should be applied until the crop has fully emerged to avoid crusting. Once the crop reaches the vegetative stage, moisture levels should be increased to near field capacity. The point here is that once the crop develops to the point of pre-flowering, soil moisture should be kept at a level which will minimize stress. This will allow irrigators to avoid continuous irrigations during flowering and potential disease problems caused by wet soil surface conditions. Canola will use large amounts of moisture during flowering, and once an irrigator falls behind it is difficult to catch up. Pivot irrigators should continue to irrigate this crop until flowering is complete.

Wheel Lines
Good spring soil moisture conditions for seed germination are a must for high yields. If poor moisture conditions exist in the spring, it is possible to apply a light application (3 to 4 hr. set). The most significant issue with using wheel lines to ‘irrigate up' canola is the potential for crusting, which will significantly inhibit emergence. Once the crop fully emerges, irrigation should start and moisture levels should be increased in the entire root zone. Timing of the second and possible third irrigation is critical as it may become difficult to move wheels through this crop after elongation and flowering begin. It is important that the root zone is filled and available moisture is not limiting during elongation. This may mean crossing the field with 4 to 6 hour sets during the last week before elongation.

Flood Irrigation
Flood irrigate canola twice during the growing season, depending on spring soil moisture and climatic conditions. The key problem with growing canola on flooded ground is having sufficient spring moisture for seed germination and getting the crop into the vegetative stage. Flooding the crop earlier could cause damage to the crop by drowning or washing the young plants out of the ground. For these reasons, flooding is the least recommended irrigation method for canola. The most important times to flood irrigate canola, if soil moisture is limited, is during the late vegetative stage and during early to mid blooming. Moisture stress during the late vegetative to spiking stage can cause uneven growth and reduced yields.

Regardless of irrigation method, the most important time to ensure adequate soil moisture is during flowering. Stress during this time causes canola to abort flowers, significantly reducing yield.

Experience and Research Have Shown....
  • Moisture stress prior to or during flowering cause the highest yield reductions.
  • Canola continues to use soil moisture until full maturity. Keeping soil moisture levels at or above 75% increase the potential for lodging.
  • Maintaining good soil moisture conditions will lengthen the flowering period, increase the number of seeds per pod, increase seed weight, and in some instances improve oil quality and content.
  • The last irrigation should be completed by the 1st week in August. Irrigation past this point delays maturity and increases the risk of frost damage.

Varieties
Admittedly, some of the varieties developed for Canadian conditions might not be suitable the U.S., but a review of the Agriculture and Agri-Food Canada web page listing "Canola Varieties for Irrigation" offers some good insights into canola production. Out of a list of 27 canola varieties with yield data collected for periods of as much as 15 years, yields ranged from 30.4 to 53.6 bushels per acre among varieties. Hence, variety does make a difference. Oil percentage averaged 44% among the 27 varieties, with a range from 43 to 48%. The 27 varieties were also ranked with respect to lodging susceptibility and on a scale from 1 (very low lodging) to 5 (100% lodging), the ranking ranged from a low of 1.0 to a high of about 2.6, except for one outlier at 4.0. Hence, it pays to know the performance characteristics of the variety you select and plant.