Effect of combined K and N application on yield, qualities and K absorption of ginger

Field experiment was carried out to study the effect of combined potassium (K) and nitrogen (N) application on yield, qualities and K uptake in ginger（Zingiber officinale） rhizome. The results showed that there was an obvious response of ginger growth and qualities to the combined N and K application. A suitable rate and ratio of K and N combined application could obviously promote ginger growth, increase rhizome yield, improve nutrition qualities and enhance K recovery efficiency. The rhizomatous yield and its components increased with the increase of K application rates as it applied with less than K2O 450 kg/hm2. The largest values of plant height, branches number, stem diameter, dry weight of shoot and weight of single rhizome were found in K450 (medium K application rate),. The maximum rhizomatous yield was attained by the treatment of N450K450. The results of quality analyses indicated that a suitable K and N application ratio could improve the nutrition qualities by increasing the content of vitamin C and sugar and dropping the concentration of nitrate in ginger rhizome. Combined application of N and K increased the content of vitamin C in rhizome compared single K application, and the highest content was obtained by the treatment of K450. But there were no significant effects of raising N application rate to vitamin C. K application increased the concentration of soluble sugar and sucrose, but it differed with the combined N and K application rate. The concentration of nitrate increased significantly with the increase of N application rate at low K application, but it showed an opposite trend with high K application rate. The lowest content of nitrate was attained in N375K375 and N450K450. K application significantly improved the concentration of K in ginger shoot, rhizome and total plant, and enhanced K absorption compared to control. The concentration and uptake of K in ginger shoot, rhizome and total plant also increased obviously as increased N application rate at the same K application rate. The agricultural efficiency of K was highest in K450 and it declined with the increase of K application rate at low rate of N application. The highest K recovery efficiency was obtained in K450 with two N application rates.