Effect of drip irrigation and boron application on enhancing seed production of sainfoin (Onobrychis viciifolia) in Northwest China

Sainfoin has gained considerable attention in the forage, medicinal, and food industries due to its exceptional nutritional profile and rich bioactive compounds. However, knowledge of agricultural practices for its seed production, particularly in arid and semiarid regions, remains limited. We conducted a three-year field experiment from 2021 to 2023 to evaluate the effects of four irrigation frequencies (2, 3, 4, and 5 applications of 50 mm each) and four boron concentrations (0, 0.3 %, 0.6 % and 0.9 %) on seed yield, quality, water use efficiency (WUE) and economic benefits in sainfoin. Our findings revealed a negative parabolic relationship between seed yield and both irrigation amount and boron concentration. The highest yields were achieved with four irrigations (200 mm) combined with a 0.6 % boron application, resulting in seed yield of 696.69 kg/hm2 in 2021, 1200.94 kg/hm2 in 2022, and 1687.91 kg/hm2 in 2023. This optimal combination also exhibited superior WUE and economic benefits compared to other treatments. Higher irrigation frequency increased seed dimensions (length, width, and height), but it had a negative impact on both germination percentage and speed. The impact of boron on seed quality varied with irrigation levels. All yield components, except for 1000-seeds weight, showed significant positive correlations with seed yield (P < 0.001). A structural equation model indicated that the number of reproductive branches per plant was the most significant contributor to seed yield. Our findings enhance the understanding of the mechanisms underlying seed yield responses to irrigation and boron application in sainfoin, offering valuable insights for agronomic practices aimed at improving seed yield in sainfoin and similar crops. •Seed yield shown a negative parabolic relationship with both irrigation and boron.•The optimal combination exhibited higher seed quality, WUE, and economic benefits.•The number of reproductive branches per plant was the key contributor to seed yield.