Drought stress is one of the most significant limiting factors in crop production worldwide, and alfalfa is no exception. Dealing with droughts and water shortages can be challenging. However, there are some new tools available to alfalfa producers to help mitigate yield and profit losses.

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Donald Miller
Technical Forage Adviser / Mountain View Seeds / Nampa, Idaho
Miller was formerly the director of product development for Alforex Seeds.

Plant breeders are developing alfalfa varieties that can buffer alfalfa yields against the adverse effects of drought using what can be labeled as “climate change genetics." These genetic advancements, combined with innovative crop and water management techniques, are set to change the landscape of how alfalfa producers deal with drought while keeping alfalfa production profitable.

The following information highlights the current and future genetic improvements for drought and how they can be best utilized with new crop and water management techniques.

Genetic improvements in alfalfa for better drought performance

Current improvements

  1. Drought tolerance and water-use efficiency in alfalfa: Early genetic improvements in the 1970s and '80s enhanced alfalfa’s ability to produce economic yields with less-than-optimal moisture. 
  2. Salt tolerance: During a drought, salinity in irrigation water can worsen, resulting in an accumulation of salts in the soil profile. This buildup is generally compounded by the fact that less irrigation water is available to leach the salts out of the root zone. Salt-tolerant varieties have improved germination in saline soils and can be productive in marginal saline soils. Salt- and drought-tolerant varieties are more efficient in extracting available water from the soil profile. Therefore, varieties having both traits could enhance production and survivability during low water years.

Future improvement

3. Drought resilience: These varieties are bred to survive without irrigation during the summer months by going into a “drought-induced dormancy.” They also have the genetic resilience to return to normal or near-normal forage production once adequate moisture is available. This new class of drought-tolerant varieties should be commercially available in 2026. “Drought-resilient” varieties are being developed by Dr. Ian Ray from New Mexico State University using conventional non-GMO advanced breeding techniques. General attributes of these varieties are:

  • Less sensitivity to drought stress
  • Remain productive under reduced water allotments
  • Have more extensive root systems
  • Display mature plant vigor under deficit irrigation
  • Able to more thoroughly extract soil moisture
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The plots in the photo are part of the plant breeding process of identifying what alfalfa breeding lines have the genes for drought tolerance. Once the best lines are identified, the plants with the drought genes are crossed together to make a new potential variety. Photo provided by Don Miller.

Possible irrigation strategies

One strategy for managing irrigation with less-than-optimal water is what is often called the “starvation diet," where the available water is spread across the entire season. The disadvantage of this option is that the reduced yields of each cut may be so low they are uneconomical to harvest.

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Another option is to fully water high-value cuts in the spring and early summer. Irrigation water is then withheld for two to three cuts during the hot summer months when yields are low and water-use efficiency is poor. Withholding water during the summer months saves water for more productive cuts and places the crop into a drought-induced dormancy, enhancing the stand's survival until water is restored.

Which option is best?

Based on current wisdom, the second strategy of watering the high-value cuts and withholding water to the midsummer low-value cuts is the best option for the use of limited irrigation water. The following is the rationale behind this strategy:

  • Most of the seasonal yield is captured by applying available water to the spring and early summer cuts. In a four-cut system, the first cutting captures 35% to 38% of the total seasonal yield. These spring cuts are also the most profitable, having the highest forage quality and yield.
  • Water-use efficiency is highest in the spring and lowest in the summer. Concentrating water applications in the spring produced the most tonnage for each inch of water applied.
  • The “drought-induced dormancy” achieved by withholding irrigation water during the hot summer months allows more water to be applied to the most valuable cuts.
  • The total seasonal yields are lower with this reduced cut strategy. However, the loss in revenue is somewhat offset by eliminating the harvest-related expenses for those low-value cuts. Even with lower yields, this production strategy can provide important farm revenue during droughts.

(Note: In most production regions, plant survival following the drought-induced dormancy is generally high. However, stand losses can occur in regions with sandy soils with poor water-holding capacity and prolonged high temperatures.)

Best practices to mitigate profit losses

The following is the current thinking on how to best manage drought-tolerant alfalfa genetics when irrigation water becomes limited:

  1. Plant the best adapted drought-tolerant alfalfa variety available for your region. It should be noted, however, that this management system can also be utilized by using conventional varieties, but the greatest potential benefit will be with those varieties having some form of drought tolerance.
  2. Crop and water management of fall-planted stands can commence the following spring.
  3. Depending on the available water supply, apply full irrigation treatments to the first two to three cuts in the spring and early summer, when the water-use efficiency is greatest, and yield and forage quality is the highest.
  4. After the last full irrigation treatment, withhold water for the next two to three months to make the stand initiate a drought-induced dormancy during the less productive hot summer months.
  5. If there is some residual growth during that drought-induced dormancy, avoid taking any harvests if the crop height is 6 inches or less. If the top growth is greater than 10 inches, it can be harvested if it is economical to do so and there is at least 10% flowering.
  6. If water is available, irrigate the last fall cut to replenish root reserves going into winter.

New genetic improvements in alfalfa combined with innovative crop and water management can make alfalfa production profitable under drought conditions. This can be accomplished by shifting water to the most valuable cuts while reducing water and harvest expenses of lower-value cuts.