Effect of potassium on the agronomic traits and fruit quality of Goji (Lycium barbarum L.)

To investgate the effects of potassium (K) application on the agronomic traits and fruit quality of Lycium barbarum L. (Goji), three levels of K fertilizer, namely LK (25 g/plant), CK (50 g/plant), and HK (75 g/plant), were applied to plants in phytotron for observing and measuring relevant indicators. The investigation involved seven agronomic traits: plant height, plant stem diameter, new branch increment, yield of fresh fruits per plant, dry fruit quantity within 50 g, ratio of different grade fruits, and ratio of longitudinal diameter to transverse diameter of Goji fruits. The results showed that K application level had significant effect on ratio of the longitudinal diameter to the transverse diameter of fresh Goji fruits, and that the influence on other agronomic traits was slight. In the meanwhile, the concentrations of amino acids, betaine, polysaccharides and flavonoids of Goji fruits in different levels of K fertilizer were tested. The K treatment increased the content of glutamic acid, and decreased that of flavonoids (P < 0.05), whereas the content of other amino acids, polysaccharides and betaine were unaffected. A total of 132 flavonoid metabolites was identified. Among them, K treatment up-regulated 36 metabolites and down-regulated 30 metabolites (P < 0.05). The results provided a basis for balanced K supply to regulate the agronomic traits and nutrients of Goji fruits.