Diagnosis Of Potato Nitrogen Nutrition Based On Nitrogen Nutrition Index And Leaf SPAD

Nitrogen is one of the important factors to affect the yield and quality of potato.Rational application of nitrogen fertilizer can increase the yield of potato,improve the efficiency of nitrogen fertilizer,reduce production costs and environmental pollution.In this paper,based on the multi-site farmers surveys and field experiments for years,and understanding the potato fertilization status in the Yinshan area of Inner Mongolia,the traditional nitrogen nutrition index diagnosis method combined with non-destructive,convenient and low-cost SPAD diagnosis method was used.By analyzing the regression relationship between the two methods,the SPAD value of leaves was used to estimate nitrogen nutrition index(NNI),and then the nitrogen nutrition status of potato was diagnosed.The critical nitrogen dilution curve(Nc),nitrogen nutrition index and SPAD leaf position difference index(SL4-8)were established by analyzing the nitrogen content,biomass,SPAD value and yield distribution of potato in different years,cultivars,nitrogen levels and growth stages.A model for estimating NNI by SL4-8 was proposed.The main research results were as follows:1.The average yield of irrigated potato in the main potato producing areas of Inner Mongolia was 36 t/hm2,the nitrogen application rate ranged from 45 to 471 kgN/hm2,with an average of 225 kgN/hm2.Insufficient and excessive nitrogen application coexist.2.According to the relationship between biomass and nitrogen concentration,the critical nitrogen dilution curve of potato under drip irrigation was constructed.Kexin-1 was Nc=5.22W-0.50(R2=0.96),Shepody was Nc=5.02W-0.42(R2=0.94),Favorita was Nc=3.65W-0.51(R2=0.97).Based on the critical nitrogen dilution curve,the range of NNI of different potato cultivars was calculated to be 0.32-1.26.According to the NNI calculation results,the suitable nitrogen application rate of the tested potato cultivars was 300-450 kg/hm2 when they reached the maximum yield under the conditions of this experiment.3.With the increase of nitrogen application level,SPADL4 and SPADL8 of all cultivars showed an increasing trend,while SL4-8 gradually decreased.With the development of the growth process,SPADL4 and SPADL8 of all cultivars gradually decreased,while the values of SL4-8 gradually increased.The value of SL4-8 is not affected by the cultivar and year.4.SL4-8 and NNI are quadratic regression curves and closely related,so SL4-8 can be used to evaluate the nitrogen nutrition level of potato plants,It laid a foundation for the accurate,fast,real-time and field diagnosis of potato nitrogen nutrition and the recommendation of fertilization.