Abstract
Potassium plays an important role in improving crop growth, yield, and quality; however, choosing the right potassium fertiliser remains challenging. To determine the optimal potassium fertiliser for kiwifruit, this study investigated the effects of different potassium sources on kiwifruit yield and postharvest quality as well as plant and soil nutrient contents in an orchard in Shaanxi Province, Northwest China. Two types of potassium fertiliser were examined (K(2)SO(4) and KCl; total K(2)O = 584 kg ha(-1)) at two different application stages (basal and topdressing) under the following four treatments: basal K(2)SO(4) + KCl topdressing, basal K(2)SO(4) + K(2)SO(4) topdressing, basal KCl + K(2)SO(4) topdressing, and basal KCl + KCl topdressing. The different potassium sources had no significant effect on kiwifruit yield; however, a slight increase in yield and economic gain was observed under combined treatment with K(2)SO(4) and KCl compared to single fertiliser treatment. Meanwhile, the single fruit weight and vitamin C content of the fruit were 7.0 and 4.6% higher under treatment with basal K(2)SO(4) + KCl topdressing compared with K(2)SO(4) treatment alone, and 3.1 and 14.9% higher compared with KCl treatment alone. Moreover, application of KCl promoted potassium and chlorine absorption by both the leaves and fruit. However, no significant differences in the content of sulphate or chloride ions in the surface soil (0-40 cm) were observed between potassium sources. In contrast, in deeper soil, the content of chloride ions was highest after KCl treatment, while that of sulphate ions was highest after K(2)SO(4) topdressing. Overall, these findings suggest that the most appropriate potassium source for kiwifruit production is basal application of K(2)SO(4) followed by KCl as topdressing in the study region.