Effects of long-term phosphorus fertilization on quality and starch RVA characters in sweetpotato

A long-term located field for fertilizer experiment established in 1980 in Xuzhou were conducted to investigate the effects of long-term phosphorus (P) fertilization on quality and RVA（rapid visco analysis）characters in four sweet potato cultivars with different starch contents. There were three treatments, the CK（without fertilization), fertilizer NK and fertilizer NPK. The results show that under the long-term P treatments(between NPK and NK)in four sweetpotato cultivars，production-increasing effect is highly significant ( F=7.45, P 0.01)，the increase rate of Xushu18 production is the largest, up to 45.49%. It has an efficient contribution to protein synthesis and dry matter accumulation. The dry matter rates of four cultivars with NKP treatment are all higher than those of the NK treatment. The increased protein content of Yushu10 is the largest increase, up to 37.89%. The differences of the starch content are significant or highly significant (F=4.28，P0.01), and the starch increase rates of Xushu18 and Xushu22 are up to 57.89% and 60.1% respectively. However, There are some downward trends on sugar contents（reducing sugar and soluble sugar）in sweetpotato roots. The RVA curve of sweetpotato starch shows a typical A or C-shape. The differences of peak viscosity (PKV) are highly significant in four cultivars under the long-term P treatments (F=10.26, P0.01). There are extremely significant differences of cold paste viscosity (CPV) in Xushu 18and Xushu 25, significantly different in Yushu 10. There is significantly different of hot paste viscosity (HPV) in Xushu18, significant differences of breakdown viscosity (BDV) in Xushu 18 and Xushu 22, and the consistence viscosities (CSV) in Yushu 10 are obtained between the two treatments. Moreover, there are no significant differences of peak time and pasting temperature in four cultivars under the long-term P treatments.