Optimum fertilization for high sugar and low-nitrate pumpkin production in the Loess Plateau

The optimization design of the three ingredients(NPK) was adopt in a field experimentation on pumpkin in the Loess Plateau of Shaanxi Province. The effect of different fertilizer doses on pumpkin quality with regard NO₃^--N and soluble sugar was investigated. The results show that N has a notable effect on pumpkin NO₃^--N and soluble sugar contents; that K has a minimal effect on pumpkin NO₃^--N and soluble sugar contents. The effect of N and P interaction on sugar and nitrate contents is significant, and N and P fertilization need not be high when K supply is optimum. The optimal fertilization doses of 95～ 120 kg·hm^-2(N), 40～70 kg·hm^-2(P) and 35～80 kg·hm^-2(K) with the ratio of N∶P₂O₅∶K₂O as 1∶0.42∶0.37 keeps pumpkin NO₃^--N content lower than 200 mg·kg^-1 and soluble sugar content higher than 7%.