Alfalfa irrigation makes it possible to plant alfalfa in areas of western Western Canada where there is little rainfall. The yield of alfalfa grass is proportional to the amount of water available to the plant. Due to the long growing season, the demand for alfalfa grass water is higher than other crops. Not only can alfalfa be planted in well drained and medium texture soil, but irrigation also allows alfalfa to be planted in more types of soil. Irrigation management should consider the water requirement of alfalfa, root development, key growth stages, soil characteristics, irrigation system, and rainfall during the growing season.

The use of water varies with seasons and climatic conditions. Climate conditions affect transpiration rate, which is the amount of water evaporated from plants and soil. The amount of water used throughout the season depends on temperature, humidity, length of the growing season, soil fertility, alfalfa varieties, and harvest management.

In summer, for every ton of hay produced, alfalfa requires 127mm-152mm of water, and one ton of hay requires 446677 liters of water. Each harvest of 2.7 tons of hay per hectare requires 190mm-230mm of water. If the efficiency of the irrigation system is 75% and all water is irrigated (with zero rainfall), then 250mm-300mm of water needs to be irrigated. Precipitation can provide a portion of water in most places. A successful water management plan needs to balance the amount of water utilized by plants with the amount of water provided by rainfall and irrigation. The key is to maintain the soil moisture content above 50% of the allowable depletion amount.

The management of irrigated alfalfa is consistent in its response to water during all stages of growth. If there is no water supply, alfalfa stops growing and enters dormancy. Wait for water to return to growth. Lack of water will seriously affect the yield of alfalfa. It is important to irrigate as needed throughout the entire growing season, especially after each harvest. Because the growth after harvest is not very fast, do not use too much water during this period. Irrigation should be completed 5 days before harvesting and restored 5 days after harvesting, except for sandy soil and soil with poor water holding capacity.

Excessive water can harm alfalfa, and excessive irrigation should not be trapped on the surface, otherwise it can lead to poor ventilation and cause diseases such as crown and root rot, which can harm alfalfa. During the hot season, the damage may be very severe. To prevent plant and yield losses, alfalfa should not be left in water for more than 24-48 hours.

The appearance of alfalfa can indicate soil moisture levels. When there is sufficient water, plants grow very quickly, and alfalfa appears light green. If there is a lack of water, alfalfa appears dark green until it begins to wilt. Immediate watering can reduce yield and quality losses. If there is 50% available soil moisture in the autumn field, there is no need for irrigation in autumn. If it is less than 50%, it is recommended to irrigate once in autumn to reduce freezing damage.