Effect of phosphate fertilizer on seed yield of Onobrychis viciaefolia and soil in Linxia, Gansu Province

To improve the seed production of Onobrychis viciaefolia in the rainfed alpine region of Gansu Province, explore the effect of phosphorus on the soil and seed production, and determine the optimal phosphorus dosage in this area, we studied the effects of different phosphorus (P₂O₅) levels (C₁: 135 kg·ha⁻¹, C₂: 90 kg·ha⁻¹ was applied in twice, C₃: 90 kg·ha⁻¹, C₄: 45 kg·ha⁻¹, CK: 0 kg·ha⁻¹) on the seed yield and seed-yield-related traits of O. viciaefolia, and on soil nutrient changes. The results showed that phosphorus application increased plant height, inflorescence number, pod number, and seed yield of O. viciaefolia. The seed yield of C₁, C₂, C₃, and C₄ increased 16.18%, 25.00%, 17.65%, and 2.32% compared with those of CK, respectively, the available N of C₁, C₂, C₃ and C₄ increased 10.31%, 11.31%, 13.61%, 6.53%, the available K of C₁ increased 5.51%. Phosphorus application increased soil available N and available K. Compared with the CK group, C₁, C₂, C₃, and C₄ dropped 8.08%, 7.25%, 5.33%, 11.23%, and 16.67%, respectively; the available K of C₁ increased 5.52%. Phosphate caused a substantial increase in the available P. The contents of available P in C_1, C₂, C₃, and C₄ increased 356.69%, 98.16%, 62.60%, and 52.32% compared with that in the CK group. In the greening and early flowering stages, P₂O₅ 45 kg·ha⁻¹ is an ideal application for seed production in the rainfed alpine region of Gansu Province.