Alfalfa growth tactics for wet springs

By Scout Nelson

Craig Sheaffer, Extension forage agronomist, along with Krishona Martinson, Extension equine specialist, and Claire LaCanne, Extension educator-crops, offer insights into managing new alfalfa stands this spring. Minnesota's unusual spring weather, marked by above-normal rainfall, has posed unique challenges for alfalfa seedlings, including issues with soil crusting, seed washouts, and flooding.

Excessive rainfall can hinder alfalfa seedling emergence and persistence. Soil crusting, particularly in medium and heavy textured soils, can prevent or delay seedlings from breaking through the soil surface. Managing seeding depth is crucial to avoid these issues, ideally not exceeding ¼ inch.

Erosion from heavy rainfall can wash away shallow-planted seeds and dislodge small seedlings. Companion cropping can be an effective strategy to mitigate erosion on vulnerable soils.

Flooding, meanwhile, harms plants by creating an anaerobic environment, inhibiting respiration and nitrogen fixation in alfalfa seedlings. Flooding can be particularly damaging to germinating seedlings and those in early growth stages.

Employing disease-resistant varieties and fungicide-coated seeds can help manage root diseases in wet conditions.

Previous crops treated with herbicides may also impact alfalfa stands. The persistence of herbicide residues depends on moisture and microbial activity in the soil. If herbicides were used in previous seasons, it's essential to adhere to rotation restrictions to prevent damage to alfalfa crops.

For new alfalfa seedings, ideal plant populations should reach 30 to 35 plants per square foot by fall. A range of 15 to 25 plants per square foot at the start of the first production year is acceptable for maximum yields. It's crucial to assess your stands by counting plant numbers across different areas within the field to ensure adequate population levels.

For fields with inadequate populations, options include tilling and reseeding or interseeding using no-till methods. No-till seeding can help maintain soil structure, reduce erosion, and ensure effective seed placement.

Although optimum spring seeding dates have passed, the existing soil moisture levels still allow for successful late seeding until mid-July. If late seeding is not feasible, another strategy is to harvest or mow the current crop 60 days after planting and then seed immediately afterward to ensure good stand establishment.

This comprehensive approach to alfalfa stand management helps producers overcome the adversities of an unusual spring, ensuring the development of robust and productive alfalfa fields.

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