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Irrigation Management of Sugar Beets

 
 
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 Introduction
Sugar beets consume up to 560 mm (22 inches) of water during the growing season. The seasonal water requirement varies depending on plant density, soils, climate and weather conditions; as well as, irrigation and crop management. Soil moisture levels should be maintained above 65% available moisture. Sugar beets develop in an active root zone of 1.0 metre (3.3 feet) with 70% of the water being drawn from the top 60 cm (2.0 feet) of this root zone. It is important to maintain adequate soil moisture levels from two to three weeks after seeding until two weeks prior to harvest. Sugar beets are most sensitive to moisture shortages in the early growing stages but their peak moisture use comes late in the season when they have complete ground cover. Over the peak 30 day growing period (July 21 - Aug.20), maximum water use is 6 mm/day or 0.24 inches/day. Maximum use during a 10-day peak will reach 7 mm/day (0.28 inches/day). A dark green colour of the beet leaves is an obvious sign of stress; and, irrigation should be started immediately, as moisture stress reduces the growth rate of the storage root. There is a positive relationship between water use, root development and sugar content. Soil moisture should be monitored on a weekly basis using a soil auger. Under irrigating will cause stress and reduce yield, while over irrigating near harvest reduces sugar content. Irrigation management of this crop is influenced by the method of irrigation you are using.

Pivot irrigation systems
Center pivots are an excellent "tool" when irrigation is required for germination. The sugar beet's small seed size and shallow planting depth make uniform germination a real challenge for growers with dry seedbed conditions. Whenever possible, irrigation for germination should be applied before seeding. If this is not possible, then several light applications may be necessary to obtain uniform germination. Large amounts of water may cause soil crusting and cool soil temperatures. A firm, moist seedbed will lead to good germination and a better stand. Some pivot operators underestimate the amount of water applied to the crop, which can lead to a fairly rapid depletion of the soil moisture in the top 50 cm (1.6 feet) of the root zone. Due to economic reasons, most pivot systems are not designed to keep up to the sugar beet water consumption during peak use. Because of this, early spring or fall irrigation is recommended to build-up moisture levels in the lower root zones. Good moisture in the lower root zone provides a buffer in case of a sprinkler breakdown or other unforeseen circumstances.

Wheel move irrigation systems
Under normal growing conditions, a producer can expect to irrigate a sugar beet crop three to five times during the growing season. The number of irrigations is dependent on nozzle size of sprinklers, rainfall and soil moisture holding capacities. A four or six-hour set may be required to fill the top 50 cm (1.6 feet) of the root zone before the sugar beet plants have 100% ground cover. During peak moisture use, near the end of July and the first two weeks of August, the beets will use upwards of 50 mm (2 inches) per week. Most wheel move systems require 15 days to apply 65 mm (2.5") to 75 mm (3") of water to a 160-acre field. During peak use, irrigations should be carefully managed to ensure proper available moisture. It is important to plan the final irrigation as both wet and dry conditions will hamper harvesting.

Surface Irrigation Systems (furrows)
A producer can expect to irrigate sugar beets three to four times during the growing season. The main problem with surface irrigation is ensuring good soil moisture for plant germination and seedling growth. Planning a fall irrigation in the previous year is a good management practice. Depending on rainfall, soil texture and weather conditions, most surface irrigators will apply their first irrigation near the end of June.

Experience and research have shown
  • A mandatory four-year rotation is in effect for sugar beets or host crops of the beet cyst nematode.
  • Sugar beets are sensitive to soil salinity during the germination and seedling stage.
  • Wilted or moisture stressed beets tend to be more difficult to store and process.
  • An average yield for sugar beets is 17 tonnes/acre to 20 tonnes/acre. Top producer yields are as high as 23 tonnes/acre to 27 tonnes/acre.
This information was prepared by the Irrigation Branch.

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Old Agdex Reference. 561-6.		  
 
 
 
For more information about the content of this document, contact Alan Efetha.
This document is maintained by Deb Sutton.
This information published to the web on June 21, 2002.
Last Reviewed/Revised on February 12, 2008.