Effects of different seeding rates on seed yield and components of alfalfa

In order to determine the optimum sowing rate of alfalfa seed field in a semi-arid area of the Ningxia region, a single factor randomized block design was used to study the effects of different sowing rates (S₁: 1.2 kg·ha⁻¹, S₂: 1.8 kg·ha⁻¹, S₃: 2.4 kg·ha⁻¹, S₄: 3.0 kg·ha⁻¹, S₅: 3.6 kg·ha⁻¹) on alfalfa seed production performance and composition factors. Plant height, number of primary branches, number of inflorescences per reproductive branch, number of spikelets per inflorescence, number of pods per inflorescence, number of reproductive branches per unit area, number of seeds per pod, 1 000-grain weight, actual seed yield, and the performance seed yield of alfalfa were significantly affected by sowing rate (all P < 0.05). The number of reproductive branches per unit area, number of inflorescences per reproductive branch, number of pods per inflorescence, number of seeds per pod, and the 1000-grain weight were the highest under S₄ sowing rate (177.09, 23.35, 12.56, 6.16, and 1.88 g, respectively). Plant height and number of spikelets per inflorescence reached their maximum under S₂ sowing rate (87.81 cm and 18.18, respectively). The above indices initially increased and then decreased with increasing seeding rate. Seed and actual seed yields were the highest under S₄ treatment (5993.39 and 630.68 kg·ha⁻¹, respectively), representing respective increases of 180.25% and 38.41% compared with S₁ treatment. Correlation analysis revealed that the number of inflorescences per reproductive branch was positively correlated with the number of spikelets per inflorescence and seed yield (S₄ > S₃ > S₂ > S₅ > S₁). The findings suggest that the best sowing rate for alfalfa seed production in the semi-arid area of Ningxia is 3.0 kg·ha⁻¹.