Effects of nitrogen fertilization rate and seeding density on the forage yield and quality of autumn-sown triticale in an alpine grazing area of the Qinghai-Tibetan Plateau, China

‘Gannong No. 2’ triticale (×Triticosecale Wittmack) is a cold-resistant annual forage crop variety, which can be planted as artificial pasture to solve the problem of forage shortage in the Gannan alpine grazing area of the Qinghai-Tibetan Plateau. However, the optimal nitrogen fertilization rate and seeding density for obtaining high yield and quality forage are still unknown. In this study, the effects of nitrogen fertilization rate and seeding density on the forage yield and quality of autumn-sown ‘Gannong No. 2’ triticale were studied. We used a split-plot design, with five nitrogen fertilization rates assigned to the main plots, namely 0 (A1), 120 (A2), 240 (A3), 360 (A4), and 480 kg N ha⁻¹ (A5), and five seeding densities assigned to subplots: 506 × 10⁴ (B1), 675 × 10⁴ (B2), 843 × 10⁴ (B3), 1011 × 10⁴ (B4), and 1180 × 10⁴ seeds ha⁻¹ (B5). Significant differences in lodging rate, tiller number, hay yield, crude protein content, neutral detergent fibre, and relative feed value were observed at different fertilization levels. Significant differences were found in lodging rate, plant height, tiller number, hay yield, contents of neutral detergent fibre and acid detergent fibre, dry matter digestibility, and relative feed value among the seeding density treatments. The interaction of nitrogen fertilization rate and seeding density significantly affected forage yield and quality, with the A3B3 treatment having the highest comprehensive evaluation value. In alpine grazing areas of the Qinghai-Tibetan Plateau, 240 kg N ha⁻¹ and 843 × 10⁴ seeds ha⁻¹ should therefore be used for autumn-sown triticale.