Fall Nutrient Care Supports Nebraska Alfalfa Success

By Scout Nelson

As the harvest season winds down, October provides an ideal opportunity for producers to collect soil samples and plan alfalfa fertility for the next growing season. Alfalfa removes large quantities of nutrients annually, and maintaining proper soil fertility is critical to ensuring stand vigor, forage quality, and long-term persistence.

According to the Nebraska Extension NebGuide EC155, a five-ton alfalfa crop removes approximately 50 lbs. of phosphorus (P₂O₅), 300 lbs. of potassium (K₂O), and 40 lbs. of sulfur (S) per acre. Without replenishment, nutrient depletion can lead to slower regrowth, reduced winter survival, and weaker stands.

Phosphorus supports strong root systems and stands health. If soil tests are low, 60–80 lbs. P₂O₅ per acre applied in the fall is recommended. Common fertilizer sources include monoammonium phosphate (MAP) and diammonium phosphate (DAP), with MAP preferred for seed-placed applications.

Maintaining a soil pH between 6.5 and 7.5 is essential, and lime should be applied to soils below 6.2.

Potassium plays a key role in stand persistence and winter survival. Fields testing below sufficiency benefit from 120 lbs. K₂O per acre, which can extend stand life by several years. Sulfur deficiencies are common in sandy or low organic matter soils, particularly in the Sandhills and northeast Nebraska. Applying 30–40 lbs. S annually or 100 lbs. every three years maintains protein levels and overall plant health.

Boron is another essential micronutrient. While deficiencies are uncommon, 1–3 lbs. per acre every other year can prevent yield losses. However, care must be taken to avoid toxicity, especially in irrigated fields where boron may already be present.

The best time to apply nutrients is from mid-October through early November, allowing fertilizers to settle before dormancy and support early spring growth. Early spring or post-harvest top-dressing may be used if fall applications are missed.

Though fertilizer costs are significant, under-fertilizing alfalfa is more expensive in the long term. Research shows correcting deficiencies can return $1.50 to $2.00 in forage value per dollar spent, proving that sound fertility management is a profitable investment.

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