Effects of HA-K fertilizers on the absorption and utilization of potassium and the storage root yield in sweet potato for table use

Sweet potato belongs to the crop favoring potassium. The storage root yield is often increased significantly by the application of potassium fertilizer. Humic Acid（HA）can promote crop growth and increase fertilizer utilization．The objective of this study was to clarify the effects of the combined application of HA and potassium fertilizer on the absorption and utilization of potassium and the storage root yield in sweet potato for table use．The variety “Beijing 553”, a wide-planted variety for table use in China，was grown in the field at agricultural experiment station of Shandong Agricultural University in 2005，and two kinds of HA-K fertilizers were applied in the field experiment．The changes of T/R ratio in plants, N/K ratio in leaves and storage root, and storage root thickening rate during storage root development and their relations with storage root yield were determined by using the methods of periodic sampling during storage root development and measuring yield at harvest．The differences in potassium efficiency for production and potassium utilization efficiency among treatments were analyzed．The results showed that potassium fertilizer application reduced the T/R ratio in plants and N/K ratio in leaves and storage roots，increased storage root thickening rate, biomass yield and its distribution in storage roots, and storage root yield (by 24.18%)．Applying HA decreased the N/K ratio in storage roots and increased the N/K ratio in leaves，storage root thickening rate and biomass yield, and storage root yield (by 5.7%)．At the same time, applying HA increased potassium efficiency for the production of biomass and storage roots．Compared with application of same rate of K2O，applying HA-K fertilizers decreased T/R ratio in plants and N/K ratio in leaves and storage roots，and increased storage root thickening rate at the early stage and medium stage of storage root development. The storage root yield was increased by 8.11%–9.50%. Moreover, the recovery efficiency and agronomic efficiency of HA-K fertilizer were all increased significantly.