Trait-specific sources of variation reveal a two-level strategy for oat grain yield improvement across environments

The soil is classified as calcareous chestnut soil. The Baotou site was located at the Science and Technology Park of Inner Mongolia Agricultural University in Beizhitu Village, Tumed Right Banner (40.48° N, 110.55° E; 993.5 m above sea level). The site has a continental semi-arid monsoon climate, with a long-term mean annual temperature of 7.1 °C, annual precipitation of 350 mm, annual sunshine duration of 3056 h and a frost-free period of 132 d.

The growing degree days (≥ 5°C) for oats during the growing seasons of 2022 and 2023 were 1,363.5°C·d and 1,427.5°C·d, respectively. The soil is a sandy-loam meadow soil developed on alluvial deposits of the Yellow River floodplain. The Hohhot site was located at the Oat Science and Technology Backyard in Wuchuan County (41.13° N, 111.35° E; 1627 m above sea level).

The site lies in Shangtuhai Town on the northern foothills of the Yinshan Mountains and represents a semi-arid agricultural environment. The long-term mean annual temperature was 2.6 °C, mean annual precipitation was 350 mm, and the frost-free period was 120 d. The growing degree days (≥ 5°C) for oats during the 2023 growing season totaled 1,422°C·d.

The soil has a sandy-loam texture. At each site-year, the experiment was arranged as a randomized complete block design with four blocks. The study included 14 oat cultivars representing the major oat-growing regions of northern China (Table 1).

Each experimental plot measured 18 m² (4.0 m × 4.5 m). The sowing is conducted by artificial seeding, with the sowing quantity of oat being 150 kg·ha-1, and the application of basic fertilizer 150 kg·ha-1 (NH₄)₂HPO₄. The sowing depth is 3-5 cm and the row spacing is 25 cm.At Ulanqab, sowing was conducted on 17 May 2022 and 18 May 2023, and harvest began on 18 August 2022 and 22 August 2023, respectively.

At Baotou, the corresponding sowing dates were 22 April 2022 and 30 March 2023, and harvest began on 14 July 2022 and 20 July 2023. At Hohhot, the crop was sown on 24 May 2023 and harvest began on 6 September 2023. Individual plots were harvested when the corresponding cultivar reached maturity.