Forage harvest intensification improves feed nutritive value without reducing grain yields in organic Kernza

Abstract

Managing Kernza [ Thinopyrum intermedium (Host) Barkworth & Dewey] as a dual‐use crop for grain and forage has potential to improve economic viability, particularly in organic systems where premiums and diversified outputs can enhance profitability. We evaluated how the timing and frequency of Kernza forage harvest affected grain and forage yields, forage composition, and weed pressure in organic systems. A 4‐year study (2020–2023) was conducted across five diverse environments in the US Midwest. Four forage harvest strategies coupled with an annual grain harvest were evaluated: (1) a single summer harvest (1x‐Su), (2) spring and summer harvests (2x‐SpSu), (3) fall and summer harvests (2x‐FaSu), and (4) fall, spring, and summer harvests (3x‐FaSpSu). Forage harvest timing and intensity affected forage nutritive value more than grain or total forage yields. Strategies including spring harvests (2x‐SpSu and 3x‐FaSpSu) improved overall nutritive value by increasing total crude protein from 5%–6% to 10% and increasing total relative feed value from 70–80 to 80–92 compared to summer harvest alone (1x‐Su). Grain yields were impacted by stand age, declining substantially over time, ranging from 385–860 kg ha ⁻¹ in Year 1 to 45–224 kg ha ⁻¹ in Year 4 across sites, while forage yields remained relatively stable (2.8–4.8 Mg ha ⁻¹ in Year 1 to 2.2–7.5 Mg ha ⁻¹ in Year 4). Weed biomass was similar among treatments but increased in Year 4, which can be a consideration for termination timing of Kernza. Our findings show that well‐timed forage harvests may improve forage quality without sacrificing productivity, offering organic farmers more flexible and profitable management for this perennial grain crop.