Tips for Maximizing Alfalfa Growth in Minnesota's Challenging Seasons

Craig Sheaffer, an Extension forage agronomist, discusses the resilience of alfalfa in Minnesota's fluctuating climates. Despite drought and elevated temperatures, alfalfa remains resilient and enhances its winter survival capabilities. This is due to the redirection of carbohydrate energy to the plant's crowns, allowing it to endure long dry spells by entering dormancy.

Farmers are advised against irrigating alfalfa during autumn. This can trigger regrowth, upsetting the dormancy process. The consequence is reduction in the plant's free water and an uptick in the use of stored energy reserves.

Before diving into alfalfa harvesting, it's important to consider several factors:

• Winter Survival: Fall harvests pose potential risks to the plant's ability to survive winter. Factors like stand age, variety traits, and soil fertility play a role in influencing this outcome. Crucially, the number of harvests per season is a key determinant. Generally, a third cut is less risky than a fourth or fifth cut.
• Forage Needs and Yields: Though fall forage is of high quality, yields are often lower post multiple spring/summer harvests. Moreover, fall harvests might result in reduced yields the subsequent spring.
• Harvest Timing: To minimize risks, it's recommended to delay harvests until average temperatures drop to around 24 F, reducing the chance of regrowth.
• Stubble Significance: Leaving a stubble of a minimum of 6 inches is beneficial. It insulates overwintering crowns and helps in capturing snow to insulate the soil surface.
• Drying Times: Fall's climatic conditions can extend drying times. Opting for haylage or baleage can help mitigate this.

The fall brings about a dormancy reaction in adapted alfalfa varieties. This process, stimulated by decreasing day length and temperatures, prepares the plant for spring by forming crown buds. A balance in the starch and sugar levels in the crown and root ensures the plant has enough energy during winter.

The ideal time for alfalfa harvesting is when air temperatures hover around 24°F. Such conditions, which usually persist for several days, result in the termination of the plant's terminal buds and canopy. However, temperatures slightly above this can still allow the plant to grow.

The presence of unharvested stubble on fields is beneficial. Not only does it capture snow, but it also prevents premature soil warm-up during mid-winters. As winter progresses, the leaves fall off, and the remaining stems dry out, ensuring no compromise on the yield or quality of the upcoming harvest.

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