The Effects Of Fertilization And Planting Density On The Yield And Quality Of Superhigh Starch Potato Cultivar

In order to understand the influences of fertilization and planting density on superhigh starch content potatoes, as the theoretical basis of the cultivation techniques of higher yield and higher quality of potatoes, a new potato cultivar, Longshu No.8, was employed to invastigate the influence of phosphorus, nitrogen and planting density on yield and quality of superhigh starch content potatoes. Mathematic models describing the relationship between nitrogen(X₁),phosphorus(X₂),planting density(X₃) and the yield and quality attributes of Longshu No.8 were built via a field experiment using the quadratic general rotational combination design.The results were as follows:1. The mathematic model for three applications, nitrogen(X₁),phosphorus(X₂),planting density(X₃), and the yield(Y₁) of Longhshu No.8 was built as follow: Y₁=37.62086-2.09978X₁²-2.03013X₂²-2.67767X₃². The influencing order of three cultural factors on yield of Longshu No.8 was: planting density (X₃)> N (X₁)> P (X₂); Single factor effect analysis showed that each three cultural factor in the secondary levels had the highest yield; Too low, and too high levels could reduce the yield. Interaction effects showed that the interaction of fertilization and planting density could promote the yield when they were below 0 levels.2. Mathematic models for three applications, nitrogen(X₁),phosphorus(X₂),planting density(X₃), and the starch content (Y₂), the vitarmin C content (Y₃), the crude protein content (Y₆)of Longshu No.8 were built respectively as follow: Y₂= 26.31810-0.88225X₁²-1.20929X₂²-1.39844X₃², Y₃=249.20-13.20X₁²-15.64X₂²-26.21 X₃², Y₆=2.74606 -0.31221X₁²-0.29630X₂²-0.32812X₃². The influencing order of three cultural factors on starch content of Longshu No.8 was: P (X₂)> planting density (X₃)> N (X₁), on vitamin C content was: N (X₁) >P (X₂) >planting density (X₃), on crude protein content was: planting density (X₃) >N (X₁) >P (X₂); Single factor effect analysis showed that each three cultural factor in the secondary levels had the highest starch content, the highest vitamin C content and the highest crude protein content. Interaction effects showed that the interaction between fertilization and planting density could promote the three contents when they were below 0 levels.The mathematic model for three applications, nitrogen(X₁),phosphorus(X₂),planting density(X₃), and the soluble sugar content( Y4 ) of Longshu No.8 was built as follow: Y₄= 0.23516+ 0.05907X₁²-0.02755X₂²- 0.04346X₃². The influencing order of three cultural factors on soluble sugar content of Longshu No.8 was: N (X₁)> planting density (X₃)> P (X₂). Single factor effect analysis showed that when the three cultural factors was below 0 levels, the soluble sugar content decreased with the increase of nitrogen, increased with the increase of phosphorus and planting density; When the three cultural factors was beyond 0 levels, the soluble sugar content increased with the increase of nitrogen, decreased with the increase of phosphorus and planting density. Interaction analysis showed that soluble sugar content≤0.2% with the interaction between nitrogen was 105.44¹94.62kg/hm² and non-phosphate or phosphate was 270 kg/hm², and soluble sugar content≤0.15% with the interaction between nitrogen was 105.44¹94.62kg/hm² and planting density was 30,000plants/hm² or 52,500 plants/hm²; Soluble sugar content decreased with the interaction between phosphate was more than 135kg/hm² and planting density was more than 52,500 plants/hm².The mathematic model for three applications, nitrogen(X₁),phosphorus(X₂),planting density(X₃), and the reducing sugar content (Y₅) of Longshu No.8 was built as follow: Y5= 0.13564+0.02014X1-0.02137X2+0.02943X₃². The influencing order of three cultural factors on reducing sugar content of Longshu No.8 was: P (X₂)> N (X₁)> planting density (X₃); Single factor effect analysis showed that the reducing sugar content increased with the increases of nitrogen, reduced with the increases of phosphorus. Reducing sugar was highest content when planting density was at 0 level. Interaction effects analysis showed that the interaction of nitrogen and phosphorus could reduce the reducing sugar content; Longshu No.8 has the minimum reducing sugar content (≤0.15%) with the interaction of nitrogen rated of 60.9²39.25kg/hm² and planting density of 30,000⁵2,500 plants/hm², or with the interaction of the phosphate rated of 0¹35kg/hm² and planting density of 30,000 52,500 plants /hm².3. By the simulation of the DPS, the cultivation program in high yield and top quality of Longshu No.8 was: pure N rateing of 120.96～137.8kg/hm², P₂O₅ rateing of 126.7～160.68 kg/hm², planting density rateing of 49,958～56,781 plants/hm². Cultivating Longshu No.8 in the humid region of high-elevation of south Gansu province with the program, the yield would be more than 32t/hm², starch content would be more than 23.9%, vitamin C content would be more than 200mg/kg, and crude protein content would be greater than 2.75% .