Comparison of various fertilizer recommendations for forage crops in the Western United States

Abstract Farmers often use private and public labs, crop advisors, or fertilizer dealers to determine fertilizer needs for crops, with recommendations and resulting costs from these sources having the potential to vary greatly. Twelve on‐farm trials across the state of Utah in alfalfa (Medicago sativa), small grain forage, and silage corn (Zea mays) were established in 2021 to compare fertilizer recommendations from five labs and a nonfertilized control, two public labs (Utah State University and University of Idaho), and three commercial labs in the Western United States, with some sites being replicated in 2022–2023. A baseline soil sample from each field was split and sent to multiple labs for analysis and corresponding nutrient rates recommended by each lab applied at each site. Fertilizer recommendations from the five laboratories varied greatly, both for types of nutrients and rates recommended, with differences between highest and lowest treatment costs ranging from 528 to 2024 ha −1 across sites. Crop yield and forage quality data were collected from sites from 2021 to 2023, with fertilizer treatments having little to no impact at four silage corn or five alfalfa sites. Yield was increased by at least one private and university lab at all three small grain forage sites and crude protein content was increased at sites with multiple years of data. Fertilizer treatments occasionally improved forage yield and quality but not crop market value. The results of this study demonstrate that growers should be aware when selecting fertilizer recommendations, and opportunities exist for better public‐private coordination of science‐based recommendations.