Abstract:

The aim is to explore the effects of different planting densities and different ratios of nitrogen, phosphorus and potassium on the yield and commodity rate of sweetpotato, in order to provide references for its high-quality and high-efficiency production. In 2019 and 2020, the new double-use sweetpotato variety ‘Zhenghong 23’ was used as the material, 7 density levels, 7 nitrogen, phosphorus and potassium ratio levels, and 49 treatment combinations were designed in the experiment. Results showed that the planting density significantly affected the yield and commodity rate of sweet potato. Along with the density increasing, the yield first increased and then decreased, and the commodity rate gradually decreased; the yield had an extremely and significantly positive correlation with the commodity rate, a significantly positive correlation with the number of potatoes per plant, and an extremely and significantly negative correlation with the fresh weight of shoots and leaves and shoot-to-root ratio. The commodity rate had an extremely and significantly positive correlation with the fresh weight of stems and leaves, the fresh weight of roots, the fresh weight of commodity tubers, the number of commodity tubers, the fresh weight of single commodity tuber and the number of tubers per plant, respectively, and an extremely and significantly negative correlation with the shoot-to-root ratio. The yield of 30,000 plants/hm ²was the lowest, followed by 75,000 plants/hm², and the yield of 45,000 plants/hm² was the highest, followed by 52,500 plants/hm². Although the commodity rate gradually declined with the increase of density, it could reach more than 90% at a density level of 45,000 to 52,500plants/hm². Different ratios of nitrogen, phosphorus and potassium had extremely significant effects on yield and the commodity rate, N:P:K=1:1:2 had both the highest output and commodity rate, followed by N:P:K=0.8:0.8:2. A two-year experimental study showed that when the planting density of sweet potato was 45,000 -52,500 plants/hm², and the ratio of nitrogen, phosphorus and potassium was N(0.8-1):P(0.8-1):K(2), the yield was the highest, reaching 22611.41 -22933.57 kg/hm², and the commodity rate was 90.40%-92.30%. Therefore, with the above density and nitrogen, phosphorus and potassium fertilizer ratio, sweet potato planting could obtain high yield and better commodity rate.

Key words: sweet potato, density, ratio of nitrogen,phosphorus and potassium, yield, commodity rate