Effects of different fertilizers on nutrient quality and mineral elements in different economic forage groups in Qilian Mountain alpine meadows

The objective of this study was to examine the responses of nutrient quality and mineral elements of forages in different economic groups forages in the Qilian Mountains alpine meadows to different fertilization treatments. Eight fertilization treatments, potassium (K), nitrogen (N), zinc (Z), boric (B), copper (Cu), phosphorus (P), molybdenum (Mo), and selenium (Se), were sprayed onto forage roots, and no fertilizer was applied as a blank control (CK), with four replicates in each group. The forage trace element contents and nutritional quality of each economic group in to different treatments were determined in mid-August, and the trace element surplus and deficiency were analyzed. Compared with that in the control, the forage crude protein (CP) content in different economic groups under different fertilization treatments increased and fluctuated within the range of 7.7%–23.94%. The dry matter digestibility (DMD) ranged from 38.78% to 77.34% and showed no significant differences in DMD among treatments (P > 0.05). The DMD of legume forages was significantly higher than those of Gramineae grasses and sedges; there were no significant differences in forage acid detergent fiber (ADF) between any treatments and the control (P > 0.05), but ADF showed a decreasing trend in the treatments compared with that in the control. The P content increased by 81.81% in legumes (P < 0.05); however, it decreased by 38.46% and 61.29% in wilted grass and forbs (P < 0.05) and increased in Gramineae grasses and legumes under N treatment by 92.86% and 50% (P < 0.05), respectively. The Cu content under Cu, N, Zn, B and Se treatments increased significantly by 33.81%∼346.49% compared with that in the control. There were no significant differences in Zn content among the economic groups under different treatments (P > 0.05), but legumes showed better absorption of Zn. Consequently, the forages in this study were evaluated as having medium Cu (8.1–20 mg/kg), medium Se (0.11–1.0 mg/kg), and medium (30.1–60 mg/kg) to high (60.1–100 mg/kg) Zn contents. Comprehensive analysis showed that the application of different fertilizers could increase the CP and DMD of various forages, reduce ADF, and effectively improve the nutritional quality of pastures. The contents of N, Cu, Zn, and Se in forages increased under all treatments, and the contents of all forage elements were at appropriate levels. Applying K, N, P, Cu and Mo is beneficial to dominant species in Qilian Mountains alpine meadows.