Accumulation and translocation of nitrogen and potassium and their relationships with yielding traits for different type cultivars of sweet potato

The experiment systematically researched the dynamic changes of nitrogen and potassium accumulations, the difference of their translocations between vines and tuberous roots in 6 types of sweet potato. The relationships between N and K contents and yielding characters were analyzed. The results suggest that the nitrogen contents of the vines of all sweet potato cultivars are decreased gradually after tuberous root formation, the content is about 2% in vines, and the nitrogen contents in tuberous roots are changed a little during thickening. The potassium contents both in vines and in tuberous roots are relatively stable. For the distributions of nitrogen and potassium, the N content in vines is far more than that in tuberous roots, while the K content in tuberous roots is far more than that in vines. For the high-starch types, the N contents of tuberous roots are from 0.68% to 0.86%, and those of vines are from 1.98% to 3.32%. For low-starch types, the N contents of tuberous roots and vines are from 0.69% to 0.86% and from 2.00% to 3.17% respectively. Correspondingly, for the high-starch types, the K contents are from 5.83% to 6.66% and from 3.19% to 3.70%, and for the low-starch types, the K contents are from 6.12% to 6.36% and from 3.48% to 3.90%. For the all types, the K contents in roots are significantly and positively related with the N contents in roots, and the K contents in vines are closely related with the K ratios of R/T negatively. For the high-starch types, there are significantly and positively correlation between the N contents in vines and percentages of dry matter, and between K ratios of roots to tops and commercial percentages, while there is remarkably negative correlations between the K contents of roots and biomass. For the low-starch types, there are markedly positive correlations between the N contents in vines and biomass, and between the K contents in vines, biomass and starch yield, while there is notably negative correlation between the K contents in vines and starch yields.