As with any cash crop, reducing stress and following best management practices is the best way to protect alfalfa in a drought situation. Setting the stand up for success by soil testing and maintaining proper P and K levels, scouting regularly for insects, and keeping an eye out for fungal diseases are all ideal ways to help reduce plant stress and boost yields. Minimizing field traffic as much as possible will also help to reduce additional stress on alfalfa stands.
Although we can’t control our precipitation with dryland alfalfa, we can apply the previously mentioned practices as well as control our cutting schedule to help protect the stand we have. A dry year likely means forage could be in short supply, so producers will be looking for tonnage. However, depending on the goals of your operation, it may be ideal to adjust that mindset a bit if conditions continue to be dry.
With roots mainly concentrated in the top 4 feet of soil but some reaching depths of up to 16 feet, alfalfa persists better than many other crops as it can find moisture lower in the soil profile. Alfalfa has a relatively high water-use rate at 0.1 to 0.3 inches of water per day depending on growth stage and other environmental factors. To ensure stand persistence, we want to protect the roots as much as possible. Once a stand reaches full bloom, it is generally accepted that root reserves are fully recharged, but how do we get there?
While many producers typically cut prior to full bloom to ensure higher quality alfalfa and more cuttings per season, drought-stressed stands may benefit from later and fewer cuttings to allow root reserves to build; in drought situations, stressed and delayed maturity alfalfa typically produces lower yields but higher quality feed (Table 1).
| Alfalfa trait | High stress | Medium stress | Low stress |
|---|---|---|---|
| Maturity* | 2.5 | 3.4 | 4 |
| Leaf/stem | 0.8 | 0.63 | 0.6 |
| IVDDM | 65% | 64% | 63% |
| NDF | 40% | 41% | 43% |
*Maturity: 2=vegetative; 3=early bud; 4=late bud. Source: Halim et al., 1989. Agron. J.
Keep in mind however, in drought situations, alfalfa increases carbohydrates in the crown root and will eventually go dormant to survive if drought persists. We always want to protect our crown roots, so cutting very low to the ground is not advisable, but even in drought conditions, leaving the standard 2.5-4” of stubble height is still considered acceptable to stand performance. Leaving a stubble height longer than 4” in drought conditions may seem ideal but can encourage smaller axillary buds to regrow. Although this is helpful for plant regrowth, you also want to promote crown bud growth which is stimulated by a closer cutting and shorter stubble height, making cutting height a balancing act.
No one hopes for drought, but if the season should progress into a dry one, these are some considerations to make to ensure the best possible outcome for your forage supply.
Resources
- Cassida, K. (2012, July 20). Managing alfalfa during drought. Michigan State University Extension.
- Halim, R. A., Buxton, D. R., Hattendorf, M. J., & Carlson, R. E. (1989). Water-stress effects on alfalfa forage quality after adjustment for maturity differences. Agronomy Journal, 81(2), 189–194.
- University of Minnesota Extension. (2024). Alfalfa during drought.
