Abstract:Lycium barbarum (goji) fruit is widely used as a medicinal food in China. Aiming to investigate how different types of salt ions in brackish water affected the yield, appearance quality, and nutritional quality of Lycium barbarum. A field crossover experiment was conducted in the Hetao Irrigation Area, using five representative groundwater salinity types (NaCl, CaCl2, CaSO4, NaHCO3, Na2SO4) at four concentration levels (0.1g/L, 0.5g/L, 2.0g/L, 4.0g/L), along with a total of 21 control treatments. The irrigation amount was 100mm of brackish water in Wulat Front Banner, the main production area of Lycium barbarum. Throughout the growth period, Lycium barbarum was irrigated three times. The results revealed that NaCl had the strongest inhibitory effect on the osmotic regulation of Lycium barbarum among the tested salinity types. NaHCO3 had the most significant impact on the secondary stress. CaCl2 at concentrations below 2.0g/L helped alleviate osmotic stress, while both CaCl2 and CaSO4 reduced secondary stress. The yield and dry mass of 100 grains of Lycium barbarum was decreased with the increase of concentrations of NaCl, Na2SO4, and CaSO4, reaching their peak at 0.1g/L.The yield and dry mass of 100 grains was initially increased and then decreased with the increase of concentrations of NaHCO3 and CaCl2, reaching their peak at 0.5g/L. Total sugars, flavonoids, and total amino acids were increased and then decreased with the increase of concentrations of CaCl2 and CaSO4, reaching their peak at 0.5g/L, 2.0g/L, and 2.0g/L, respectively. Betaine and total amino acids were decreased with the increase of concentrations of NaCl, Na2SO4, and NaHCO3, and significantly decreased after exceeding 0.1g/L. Carotenoid content was increased and then decreased with the increase of concentrations of CaCl2 and NaHCO3, reaching its peak at 2.0g/L and 0.5g/L, respectively, which was significantly higher than that of the control treatment. The comprehensive scores indicated that under the same anion (Cl-, SO2-4) environment, Na+ inhibited the planting benefits of Lycium barbarum, while Ca2+ promoted them. Under the same cation (Na+) environment, the inhibitory strength of different anions on the planting benefits of Lycium barbarum was observed in the order of Cl-,SO2-4,HCO-3. Based on Gaussian regression, it was found that when Na+, Ca2+, Cl-, SO2-4 and HCO-3 were ranged from 18.6mmol/L to 19.2mmol/L, 12.2mmol/L to 13.0mmol/L, 63.0mmol/L to 68.4mmol/L,6.3mmol/L to 14.4mmol/L and 5.5mmol/L to 14.0mmol/L, respectively, the planting benefit compatibility of Lycium barbarum was higher (Ci>0.7). With the improvement of Ci standard, Na+, Cl-, SO2-4, HCO-3 approached the lower limit (18.6mmol/L, 63.0mmol/L, 6.3mmol/L, 5.5mmol/L), and Ca2+ approached the upper limit (13.0mmol/L). The planting benefits remained satisfactory (with an average fit degree greater than 0.46) within the simulated range. The upper concentration thresholds were determined as 34.8mmol/L for Na+, 81.6mmol/L for Cl-, 22.6mmol/L for SO2-4, and 21.4mmol/L for HCO-3. The lower concentration threshold for Ca2+ was determined as 9.8mmol/L. These research findings provided a scientific basis for guiding the cultivation of Lycium barbarum in different water-quality areas of the Hetao Irrigation Area. The research evaluated the effects of different salinity levels of brackish water salt ions on the irrigation of Lycium barbarum and proposed suitable concentration ranges of various sensitive ions for irrigating Lycium barbarum, providing a theoretical basis for the promotion of brackish water irrigation for Lycium barbarum. The main innovation lied in the establishment of the relationship between brackish water salt ion concentration and the comprehensive benefits of Lycium barbarum through cross experiments and numerical simulations. The research findings demonstrated strong applicability in moderately saline-alkaline soils, mainly including loess and loam soils.
