In 1994, there were 300,000 ac (120,000 ha) of irrigated barley grown in Alberta. This equates to 24 per cent of the total irrigated area in Alberta. The varieties commonly grown under irrigation are: Harrington for malt, and Duke for silage and feed. Malt barley yields range from 80 - 100 bu /ac (4.3 - 5.4 tonnes/ha), feed barley 100 - 130 bu/ac (5.4 - 7.0 tonnes/ha), and barley silage 14 - 18 tonnes/ha (5.3 - 6.7 tons/ac) at dry weight basis.
The optimum time to seed barley is in the last week of April or first week of May. Depending on variety and seasonal growing conditions, barley requires 90 to 110 days to reach maturity. Late seeding will increase the risk of lower yields.
The seasonal water requirements for barley depends on variety, target yield and crop management. Barley requires 390 - 430 mm (15 - 17 in.) for optimum yield. Malt barley may require more water over the growing season than feed barley. This additional water is required to maintain the protein content of the grain and meet the standards set by maltsters.
During initial growth stages, crop water use will range from 1 - 3 mm/day rising to a high of 7 - 8 mm/day during the flag leaf to flowering stages. In soils well suited to irrigation, barley develops an active rooting depth of approximately 1.0 m (3.3 ft). By the flowering stage, full canopy cover is established and the active rooting depth has been established. Approximately 70 per cent of the crop water use comes from the top 0.5 m (1.6 ft) of the root zone, but the crop will use soil moisture to a depth of 1.0 m. Maximum water use will occur for 21 - 28 days.
To optimize yield, soil moisture levels should remain above 50 per cent of available moisture in the active root zone from seeding to the soft dough stage. Irrigators with centre pivot irrigation systems have less trouble irrigating up to the soft dough stage. However, irrigators who surface irrigate or use a side roll wheel line system need to manage irrigation differently. Surface irrigators are not limited by crop height but are generally limited by labor constraints and system design. Side roll wheel line operators are limited by crop height and time required to move the system across the field. The final irrigation may need to occur when soil moisture conditions are above the 50 per cent allowable depletion level. No matter what method of irrigation is used, adequate soil moisture conditions are needed for the entire season to ensure full crop development. In most years, irrigation of barley should be completed by late July or early August. If barley is grown for silage, final irrigation is usually completed by mid-July. .
It is important to know and be able to calculate the amount of moisture in the soil root zone in order to understand the amount of moisture available for crop use. The allowable depletion level is the amount of soil moisture that can safely be removed from the root zone by a crop before an irrigation is required. For barley, the allowable depletion level is 50 per cent of available moisture. The feel method is a simple way to determine soil moisture content. By feeling, squeezing and observing a handful of soil, one can determine the moisture present in the soil. Other methods to measure soil moisture include gypsum blocks, tensiometers and neutron probe.
Crop response to drought stress
Moisture stress at any stage of crop growth can cause an irreversible loss in yield potential. The severity of loss will depend on the timing, length, and severity of the drought period. Yield reduction can be due to loss of tillers, reduced kernel weights or fewer kernels. Research indicates that stress prior to, or just after, the onset of flowering, reduces yields the most. The yield-reducing effects of stress can be offset somewhat if the stress is relieved later in the season, but the yield recovery from stress near flowering stage is lower than recovery from stress in the vegetative stages of earlier growth. Moisture stress can also result in higher protein contents and a shortening of the grain filling period, leading to earlier maturity.
Barley is not tolerant of prolonged or excessive drought. It will tolerate soil moisture depletion to 30-35 per cent of available moisture during grain formation and 10-20 per cent near maturity. Protein content of the grain increases when available soil moisture drops below 50 per cent for extended periods of time. For optimum yield and quality, it is important to monitor soil moisture conditions regularly through out the growing season and irrigate accordingly.
Crop response to excess moisture
Excessive soil moisture during the jointing and boot stage, coupled with high nitrogen fertility, may promote vegetative growth that could result in lodging as the crop develops. Irrigation after the crop is well developed also promotes lodging due to the weight of water on the plants. Excessive soil moisture during the tillering and flowering stages will not depress yield nearly as much as during earlier stages of growth.
Old Agdex Reference. 561-15.