Effects Of Nitrogen Fertilizer On Growth And Nitrate Accumulation Of American Ginseng

Nitrogen is one of the essential nutrients elements for plant growth,and nitrogen deficiency can seriously affect the normal growth of plants.However,excessive application of nitrogen fertilizer can bring certain harm to crops,soil and water source environment.In recent years,with the continuous improvement of people~'s living,the demand of American ginseng has been increasing.To increase the yield of American ginseng effectively,the rational application of nitrogen fertilizer is one of the effect measures to improve the yield and quality of American ginseng farmland cultivation.At the same time,nitrogen is also one of the main factors for nitrate accumulation in plants,and excessive accumulation of nitrate may bring potential risks to food safety.In order to investigate whether there is nitrate pollution in American ginseng,it is necessary to study the accumulation of nitrate in American ginseng under different nitrogen application levels.In this work,two year American ginseng seeding have been choose for the field test,and five nitrogen levels were set to explore the influence of nitrogen fertilizer rates for agronomic traits,yields and active ingredients.And this work was used for understanding the nitrogen requirement law of American ginseng to determinate the optimal nitrogen application amount,and providing the basis for scientific fertilization of American ginseng cultivation.Moreover,the effect of nitrogen fertilizer on the accumulation of nitrate in American ginseng was studied to understand the relationship between the nitrogen fertilizer amount and the nitrate accumulation,to provide more theoretical basis for the safety evaluation of American ginseng in food and medicine fields.This work mainly achieved the following research results:1.N2 level of 10 g/m~2 was determined to be the optimal nitrogen level with the yield about 107.58 g/m~2 for the two-year-old American ginseng.The total soluble sugar content was 15.12%,and the fruit,grape,cane and maltose was 0.3%,0.59%,7.16%and 2.70%,respectively.The total content of 9 saponins was 3.80%,the protein content was 8.65%,the content of 16 main amino acids was 2.40%,and the nitrate content was 14.74 mg/kg.2.The leaf area,leaf weight,stem height,stem weight,root length,root diameter,root weight,SPAD and photosynthetic rate of the two-year-old American ginseng at different growth stages showed the tendency to rise first and then fall with the increase of nitrogen level,and they reached the peak at N2 level,the difference was significant at the level of P<0.05.3.The content of active constituents in the stems and leaves of the two-year-old American ginseng during the two-year-old harvest increased first and then decreased with the increase of nitrogen fertilizer dosage.The total soluble sugar had a maximum of 13.49%at N1 level,which was 31.40%higher than the control group,and the difference was significant.The total saponin content peaked at the N1 level,which was10.35%.4.In the two-year-old American ginseng root,the content of soluble total sugar was significantly increased by 25.40%of N1 and 24.24%of N2 compared with N0,but significantly decreased by increased nitrogen levels;The total saponins reached a maximum content at N2 about 4.34%increased by 18.29%compared with N0,but with no significant difference;The protein content reached about 9g/100g with slight changes at a low nitrogen level,but the accumulation was significantly reduced at a high nitrogen level of N4;The different increased degrees of amino acids were present with the increase of nitrogen level,and the highest increase value shown at N1 by22.19%compared with the control level N0.5.The accumulation of nitrate in two-year-old American ginseng increased to different degrees with the increase of nitrogen levels.The variation range of nitrate content was 14.37-32.92 mg/kg,and the variation range of nitrite content was0.94-1.47 mg/kg.6.According to the risk assessment method of pesticide residues in Polish agricultural products,the chronic exposure of nitrate residues in three-year-old American ginseng was assessed.It was found that the HQ of nitrate and nitrite in American ginseng was 0.07%and 0.11%respectively,which was far less than 100%.This indicated that there was no chronic health risk of nitrate and nitrite in American ginseng and it was safe to eat.