Optimizing Nitrogen Fertilizer Rates for Annual Cereal Forage Production
Applied Research
Joseph Sagers
Extension Educator
University of Idaho
Rigby
Abstract
Nitrogen fertilizer is essential for cereal forage production, providing significant returns but also significant costs. Understanding nitrogen requirements is crucial for maximizing yield, quality, and cost-effectiveness while minimizing environmental impact. Different annual cereal forage species and cultivars may exhibit varying responses to nitrogen availability. This study was to determine the optimal nitrogen fertilizer rate for three forage barley (Hordeum vulgare) varieties (‘Hays’, ‘Haybet’, ‘Lavina’) and three forage oat (Avena sativa) varieties (‘Monida’, ‘Otana’, ‘Ajay’). The study was conducted at the University of Idaho Aberdeen Research and Extension Center and Brigham Young University – Idaho (BYUI), Rexburg in 2021 and only at BYUI in 2022. The experimental design was a split-plot design where nitrogen rates (0, 35, 70, 105, 140 lb/ac) and variety were the main effects. At the Rexburg site, nitrogen rates significantly influenced dry matter yield in 2021 but not at the Aberdeen site, where the residual soil nitrogen concentration at planting was 141 lb/ac. Nitrogen rates had a significant effect on crude protein at both sites, although the impact varied between years. Following the first harvest, only oat test varieties showed significant regrowth, with a general decline in forage quality observed post-harvest. The optimal nitrogen rate for maximizing economic returns, taking into account pre-planting residual soil nitrogen across both locations, was determined to be between 140-175 lb/ac. Forage quality assessments showed that crude protein percentages were above 13%, indicating premium quality, while total digestible nutrients percentages were above 52%, reflecting average to good quality in 2021 but slightly declined in 2022. The optimal nitrogen rate for maximizing economic returns generally for all varieties was determined to be 175 lb/ac across both locations. The study concluded that Lavina and Haybet barley, as well as Monida and Otana oats, were the most viable options for maximizing yield. Ajay oats can be chosen if forage quality is prioritized due to their short stature and are less prone to lodging. The research highlights the importance of considering local climate, residual soil nitrogen before planting, and variety-specific responses to nitrogen fertilization when optimizing forage production strategies.
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
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Sagers, J. Extension Educator, University of Idaho, Idaho, 83442