Effects Of Nitrogen Application Rate,Planting Density And Topdressing Type On Yield And Quality Of Potato

Heilongjiang Province is a dominant area of potato production in China,but the level of production management is relatively extensive,and there is a lack of excellent varieties.The development of potato industry urgently needs efficient cultivation techniques around new varieties to improve the yield of potato and promote the upgrading of varieties.In this experiment,two new potato varieties bred independently in recent years were used to carry out research on supporting cultivation techniques,determine suitable cultivation density and fertilization scheme,and provide basic data and planting guidance for the promotion and expansion of new varieties.In this study,fresh food variety Dongnong 312 and processing variety Dongnong 321 were used as test materials.Two groups of field experiments were set up in Harbin,Heilongjiang Province.One was the two-factor experiment of planting density and nitrogen fertilizer,and 3 planting densities(A1=42 000 plants/hm~2,A2=51 000 plants/hm~2and A3=63 000 plants/hm~2)and 4nitrogen application levels(B1=75 kg/hm~2,B2=135 kg/hm~2,B3=195 kg/hm~2and B4=255 kg/hm~2)were set.The second is a single factor topdressing test,setting up 5 fertilizer treatments(CK=conventional topdressing,C1=nitrogen reduction topdressing,C2=Humic acid,C3=Organic matter and C4=Microelement Zn and Mn).The effects of nitrogen application rate,planting density and topdressing on agronomic traits,yield and quality of each variety were investigated.The results show that:(1)The effects of cultivation density and nitrogen application rate on the plant morphological indexes of the two varieties were different.At the seedling stage,budding stage and full-bloom stage,the nitrogen application rate had a very significant effect on the plant height,stem diameter,SPAD and canopy coverage of the two varieties.The cultivation density had a significant effect on plant height,stem diameter,SPAD and canopy coverage at the early flowering stage.The effect of nitrogen application rate on the above indexes was greater than that of cultivation density.(2)The nitrogen application rate had a significant effect on the yield,commodity potato yield and potato number per plant of the two varieties,and had a significant effect on the single potato weight of Dongnong 312.The yield of the two varieties increased first and then decreased with the increase of nitrogen application rate under the treatment of 75 kg/hm~2～255 kg/hm~2.The planting density had a significant effect on the yield and single tuber weight of the two varieties.In the range of 42 000 plants/hm~2～63 000 plants/hm~2,the yield of the two varieties increased with the increase of planting density,and the single potato weight decreased with the increase of planting density.The highest yield and commodity potato yield of Dongnong 312 were A3B3 treatment,and the yield and commodity potato yield were 67 197 kg/hm~2and 50 769 kg/hm~2,respectively.The yield of Dongnong 321 was the highest under A3B2 treatment,which was 60 409 kg/hm~2,and the yield of commercial potato was the highest under A1B2 treatment,which was 42 629 kg/hm~2.(3)Nitrogen application rate had significant effects on the contents of dry matter,starch,crude protein,vitamin C and reducing sugar in the two varieties.With the increase of nitrogen application rate,the contents of starch and vitamin C in the tubers of the two varieties showed a downward trend,while the contents of crude protein and reducing sugar increased.In general,high nitrogen application rate is not conducive to the formation of excellent tuber quality.The cultivation density only had significant or extremely significant effects on the dry matter and crude protein content of the two varieties.The best tuber quality of the two varieties was A1B1treatment.(4)Topdressing C3 treatment(Organic matter)could improve the plant height,SPAD,potato number per plant,yield,dry matter content,starch content and vitamin C content of Dongnong 312,and the yield was 54 748 kg/hm~2,which increased by 3.43%.The plant height,stem diameter,canopy coverage,yield,commodity potato yield,potato number per plant,starch content and vitamin C content of Dongnong 321 were increased by C1 treatment(reducing nitrogen topdressing).The yield was 51 973 kg/hm~2,and the yield was increased by 8.50%.(5)In summary,the optimum cultivation schemes of Dongnong 312 and Dongnong 321 were nitrogen application rate 195 kg/hm~2,cultivation density 63 000 plants/hm~2and nitrogen application rate 135 kg/hm~2,cultivation density 63 000 plants/hm~2.The best topdressing measure is spraying Organic matter foliar fertilizer on Dongnong 312;Dongnong 321 can be reduced nitrogen topdressing(Urea:30 kg/hm~2).