Spring wheat yields unchanged after winter pea vs winter wheat in dryland Pacific Northwest USA

The 2-year winter wheat (WW) ( Triticum aestivum L.)-fallow (F) system (WW-F) in the low-precipitation dryland Pacific Northwest (PNW) lacks diversity, increasing weed and erosion risk, whereas diversified rotations improve soil health and disrupt weed cycles. Winter pea (WP) ( Pisum sativum L.) is an alternative to WW in 3-year rotations for its deep-sowing emergence, cold tolerance, and early maturity. However, long-term SW yield responses following WW and WP remain unclear. This study assessed the effects of WP and WW on SW yield and the influence of crop rotation on yield stability. The study leveraged a 14-year-old field experiment near Ritzville, WA, USA, comparing two 3-year crop rotations: WP–SW–F and WW–SW–F, to understand soil water dynamics and SW yield following WP and WW. Winter wheat showed higher soil water storage and PSE (WW = 73%, WP = 63%) due to its taller, thicker stubble. Spring wheat yields varied across years under both rotations, with WW providing greater yield stability. Despite this, 13‑year average SW yields after WW and WP were similar, and residual nitrate‑N levels were generally comparable, although WP received no N fertilization. Although WW improved soil water storage relative to WP, this advantage did not result in higher yields. Both rotations performed similarly, suggesting that biological nitrogen fixation in WP compensated for its lower soil water storage relative to WW, leading to comparable average SW yields. Winter pea is a viable alternative to WW in 3-year rotations in the dryland PNW, USA. • Winter wheat stubble retained more overwinter precipitation than winter pea residue. • Across 13 years, spring wheat yields were similar after winter wheat or winter pea. • Winter Pea’s nitrogen fixation explains similar wheat yields despite lower moisture. • Spring wheat had slightly higher yield stability after winter wheat than winter pea. • Winter pea offers an alternative to winter wheat for rotation diversity in the PNW.