Impact of grain number and grain weight variability on autumn-sown oat yield and quality in a high-yield potential maritime climate

Oat ( Avena sativa L.) is among the most important cereal crops worldwide and is increasingly being cultivated and utilised. However, there is limited information about the physiological processes limiting yield in high-yield potential maritime climate regions that consistently produce large sink capacity in cereals. A three-year study was conducted to (i) characterise the variation in growth pattern and yield components contributing to yield in autumn-sown oat crops across sites and seasons, (ii) identify periods of development most likely to influence yield and (iii) identify grain quality characteristics that can be influenced by variations in yield and its components. Field experiments were conducted on cv. Husky at three sites with contrasting latitudes (Carlow, Meath and Cork) on the island of Ireland from 2021 to 2024. A detailed assessment programme of crop growth and development, including canopy development, light interception, biomass accumulation and nitrogen dynamics, was carried out. Across the nine sites/seasons, the grand means of 10.3 t ha −1 for grain yield, 28,651 for grain number m −2 and 36.4 mg for mean grain weight were achieved. Variability in grain number m −2 had a larger influence on grain yield than variations in mean grain weight. Plant establishment and the early season main stem number m −2 influenced harvest panicle number m −2 . Grain quality traits varied more with seasons than with the sites, showing minimal influence from variation in yield and its components. The present study shows that the grain yield of autumn-sown oat is generally sink-limited by grain number per unit area, with pre-anthesis growth rate and nitrogen uptake rate significantly influencing grain numbers. Furthermore, grain weight was found to be sink-limited, with occasional co-limitation by source-sink, and was strongly influenced by grain filling rate and duration. • The grain yield of autumn-sown oat was primarily driven by grain number m −2 . • Tiller dynamics did not influence sink size; the crop displayed a uniculm growth habit. • Pre-anthesis growth and nitrogen uptake rate influenced grain numbers. • Oat in the maritime Irish climate exhibited occasional co-limitation in the post-anthesis source-sink balance. • Grain quality traits varied more with seasons than with sites.