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Residual Nitrogen Effects on Grains Following Non-Dormant Alfalfa

Applied Research

Joseph Sagers
Extension Educator
University of Idaho
Rigby

Abstract

Alfalfa is widely recognized for its ability to fix atmospheric nitrogen, yet questions remain regarding whether non-dormant, high nitrogen-fixing alfalfa cultivars provide greater residual nitrogen benefits to subsequent grain crops than traditional dormant varieties. This study evaluated the agronomic performance and residual nitrogen effects of a non-dormant, high nitrogen-fixing alfalfa cultivar (Hi-Nitro) compared to a traditional dormant cultivar (Stratica) on spring wheat and barley production. Alfalfa was clear-seeded in Aberdeen, Idaho, in 2023 and harvested four times, with yield, forage quality, and nodulation assessed. Both cultivars achieved USDA Supreme hay quality, with Stratica producing higher yields on the first three cuttings and greater crude protein, while Hi-Nitro produced an additional fall cutting that resulted in the highest total annual yield. No significant differences in nodulation were observed between cultivars. In 2024 and 2025, spring wheat (UI Gold) and spring malt barley (ABI Eagle) were planted following alfalfa termination, with varying nitrogen rates and tillage treatments. Grain yield and protein responded positively to increased nitrogen application regardless of prior alfalfa cultivar. Wheat consistently exhibited higher grain protein than barley. Yield increased under tilled conditions, while grain protein was higher in non-tilled systems. Overall, residual nitrogen effects on grain yield and protein were similar between alfalfa cultivars, indicating that non-dormant, high nitrogen-fixing alfalfa did not provide a measurable advantage over traditional dormant alfalfa for subsequent grain nitrogen availability.

Poster has NOT been presented at any previous NACAA AM/PIC

This poster is being submitted for judging. It will be displayed at the AM/PIC if not selected as a State winner. The abstract will be published in the proceedings.

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Authors: Joseph Sagers, J. Reed Findlay, Jared Spackman, Justin Hatch, David Callister, Jared Gibbons
  1. Sagers, J. Extension Educator, University of Idaho, Idaho, 83442
  2. Findlay, J. Extension Educator, University of Idaho, Idaho, 83221
  3. Spackman, J. Barley Agronomist, University of Idaho, Idaho, 83210
  4. Hatch, J. Extension Educator, University of Idaho, Idaho, 83276
  5. Callister, D. Extension Educator, University of Idaho, Idaho, 83213
  6. Gibbons, J. Extension Educator, University of Idaho Extension, Idaho, 83440