Effect Of Nitrogen Application On The Potato Starch Accumulation And Yield In The Arid Zone Of Central Ningxia

In order to investigate the effect of different nitrogen levels on the accumulation and yield formation of potato tubers in arid region of Ningxia,the main cultivar in the southern mountainous region of Ningxia,namely Qingshu No.9 as the test material,and was designed by the single factor treatment with 4 nitrogen treatments.The effects of nitrogen rate on potato growth and development,dry matter accumulation and distribution,tuber starch accumulation and key enzyme activities of starch formation,plant nitrogen uptake and transportation,leaf photosynthetic and physiological characteristics,and yield and yield components in arid region of Ningxia were studied.The results are as follows:1.No nitrogen fertilizer inhibits the growth and development of potatoes.With the increase of nitrogen application rate,the plant height,stem diameter,and leaf area index of potato increased gradually,but high nitrogen could cause overgrowth of potato plant stems and leaves,and could easily cause late-maturing plant growth.Appropriate application of nitrogen fertilizer promotes total dry matter accumulation of potato.The highest rate of dry matter partitioning in potato tubers with a nitrogen application rate of 150 kg·hm-2,which is beneficial for the storage of dry matter before flowering of the stems and leaves of potatoes,and for the transfer and input of an assimilation product after anthesis into tubers.2.Under different nitrogen levels,the starch content in potato tubers was consistent with the slow-fast-slow "S"-shaped growth curve.The application of nitrogen fertilizer had different degrees of increase in the contents of amylopectin,amylose,total starch and key starch-forming enzymes in potato tubers.When the nitrogen application rate was 150kg·hm-2,the Tmax,Wmax,Gmax and starch accumulation rate were the highest,and the total starch content increased by 29.97%,17.24%and 9.08%than NO(No nitrogen fertilizer),N1(75kg·hm-2)and N3(225kg·hm-2)treatment,respectively;Appropriate amount of nitrogen fertilizer can promote starch accumulation in potato tubers.The activities of ADPG-PPase,SSS and SBE are closely related to the formation of amylopectin in the process of starch formation.3.The nitrogen content in different organs of potato has been gradually reduced with the progress of fertility,the nitrogen content of potato leaves,above-ground stems and tubers has gradually declined.When nitrogen application rate was 0-150kg·hm-2,the activities of key enzymes in nitrogen metabolism,nitrogen content,nitrogen accumulation,and NHI in potato tuber gradually increased with the increase of nitrogen application rate.High nitrogen is not conducive to the transfer of nitrogen into tubers.The nitrogen content of each organ showed as follows:leaf>aboveground stem>tuber.The highest nitrogen allocation rate in tubers under N2(150kg·hm-2)treatment,however under low nitrogen and high nitrogen conditions,they are not conducive to the transfer of nitrogen into tubers.The AE,PE,RE and PFP of potato gradually decreased with the increase of nitrogen application rate.4.When the nitrogen application rate was 150kg·hm-2,SPAD value,net photosynthetic rate(Pn),chlorophyll fluorescence parameter PI value and ABS/RC of potato functional leaves showed different degrees of improvement.Reasonable application of nitrogen fertilizer can reduce the senescence of potato shoots to a certain extent,which is beneficial to the accumulation and operation of photosynthetic products.No nitrogen fertilizer could increased the membrane lipid peroxidation of potato functional leaves,the cell membrane permeability,malondialdehyde,free proline and soluble sugar content increased significantly.Rational application of nitrogen fertilizer can significantly increase potato antioxidant enzyme activity.5.There are significant differences in potato yield and yield components under different nitrogen levels,application of nitrogen fertilizer is beneficial to increase the number of blocks per hole,potato weight per hole,and the number of large potatoes etc.When the level of nitrogen application was 0-150kg·hm-2,potato tuber yield and commodity potato yield increased significantly with the increase of nitrogen application rate,while continuing to increase nitrogen fertilizer will cause late-maturing potato lushness,it is not conducive to the improvement of potato production.Compared with NO treatment,the yield of potato treated with N1,N2 and N3 increased by 9.62%,17.35%,15.23%,respectively.Combining yield regression simulation equations with economic benefits,It is suggested that the best nitrogen application rate in this area is 184.11kg·hm-2.