Canola Irrigation Guide: Water Needs, Systems, and Best Practices for Higher Yields
Canola is cultivated as a dryland crop in the majority of cases. However, research and practical experience have shown that, like small grains, canola reacts positively in irrigation, producing significantly higher yields. In case a farmer decides to apply irrigation to his/her field, it is important to take into account the rainfalls, the environmental conditions, soil type, the type of canola cultivated, the water needs, and the critical stages of the plants.
How much water does Canola need?
From seed germination until pod ripening, canola plants benefit from sufficient water availability. At any moment during crop growth, irrigation should be applied just before the available soil water is depleted to 60%, bringing it near field capacity. Throughout the growing season, the crop requires approximately 400-480 mm (or 16 to 19 in) of water, with more than half of it needed near flower and pod fill, considered the most critical and sensitive stages for drought stress (1). Compared to small grain crops like wheat and barley, canola has the lowest Water Use Efficiency since, for every 25 mm (1 in) of water used, canola produces 3.5-4 bushels per acre (0.24-0.27 tons/ha) (almost half the amount compared to the other crops) (2).
For winter-type canola, one irrigation may be needed at sowing to bring the moisture of the seedbed to the desired levels and facilitate germination and plant emergence. On the other hand, rainfalls and water moisture are usually sufficient during the planting of the spring-type canola. The first growth stages are essential for successful plant establishment and leaf and root development, so water stresses at that time should be avoided. During early growth, the water use of canola is 0.1-0.8 mm (0.004-0.03 in) per day. However, as the plants grow and the weather becomes warmer, the water use peaks during the period from stem elongation until the end of pod filling, reaching 7-12 mm (or 0.3-0.5 in) per day. The lack of water during this period will result in important yield losses (3, 4). To cover these needs, usually, 4 irrigations are needed during spring, with the last one to be performed 10-15 days after the end of flowering. More specifically, early spring irrigation will increase the number of pods produced per plant, while later applications will maximize seed size and oil content. However, avoiding over-irrigation (especially over-head irrigation) during flowering is crucial since it can cause flower losses and reduce pollination (5). Using sensors to monitor soil moisture and plan irrigation is highly recommended.
Keep in mind that when canola is cultivated under irrigation, the amount of fertilizers used may be needed to increase a well and assist the plant in producing a larger canopy and higher yields.
Irrigation systems used in canola cultivation
There are four irrigation systems that can be used in fields where canola is growing.
- Overhead irrigation
- Border check
- Raised beds
- Rice layouts (it is not advised due to poor drainage)
The farmer should select the most suitable irrigation system depending on the morphology and the soil type of his/her field, as well as the water availability in the region during the growing season.
Overhead irrigation using center pivots and lateral moves is suitable for canola and should be preferred in red-brown and sandhill soil. This irrigation strategy offers higher flexibility, more frequent and lighter water applications, improved water-use efficiency, reduced risk of water logging and soil crusting, and is more environmentally sustainable. The greatest disadvantage of this method is the high cost of establishing, operating, and maintaining the system.
Border check is the most widely used irrigation system for canola since it is suitable for various soils. It is a furrow irrigation method, meaning the whole field is covered with water. The farmer should wait until the plants have grown a bit (later vegetative stages) before irrigating with this technique. Otherwise, there is a high risk of damaging the young seedlings. The field should have a slope to reduce the risk of waterlogging and a good soil surface drainage rhythm (opportunity time, around 6 hours from the moment of irrigation). The field slope should be higher if the farmer wants to use this technique in heavier soils.
Raised beds irrigation is still considered a flood irrigation type but has an acceptable drainage rhythm, and it can be used in fields with a slope of 1:1500 or less. The farmer should start forming the beds before crop sowing (6, 1, 7).
Drip irrigation is less common for canola but can be employed in regions with water scarcity. It delivers water directly to the root zone, reducing evaporation and water use. This method is particularly advantageous in sandy soils or regions with limited water supplies (8).
References
- http://www.australianoilseeds.com/__data/assets/pdf_file/0015/8016/82_GRDC_Canola_Guide_Irrigation_management.pdf
- https://open.alberta.ca/dataset/9a017865-5692-464d-92ac-93b5d50558db/resource/c0d20e0c-9f14-4f6d-8144-b8a6bc3452ba/download/5485851-2011-agri-facts-crop-water-use-requirements-revised-100-561-1-2011-11.pdf
- https://hort.purdue.edu/newcrop/afcm/canola.html
- https://www1.agric.gov.ab.ca/$Department/deptdocs.nsf/ba3468a2a8681f69872569d60073fde1/c23b310b6e0ff2d287257873004ffdb0/$FILE/149_561-1.pdf
- https://bookstore.ksre.ksu.edu/pubs/MF2734.pdf
- https://irec.org.au/wp-content/uploads/Irrigated-canola-in-southern-cropping-systems-2018.pdf
- https://waterquality.montana.edu/farm-ranch/irrigation/other_crops/canola.html
- https://www.extension.iastate.edu/alternativeag/files/documents/canola_crop_guide.pdf
Further reading
- History, Uses, and Nutritional value of oilseed rape (Canola)
- Canola Planting Guide: Soil Requirements, Seeding Rates, and Best Planting Time
- Plant Information and Variety Selection of Rapeseed
- Canola Irrigation and Water Needs
- Canola Fertilization Guide: Key Nutrients, Rates, and Application Timing
- Canola Pest and Disease Management
- Canola Weed Management
- Yield, Harvest, and Storage of Canola