The Growth, Nitrate Accumulation And Nutriment Quality Of Amaranth In Relation To Nitrogen Supply

Amaranth is one of the vegetables prone to high accumulation of nitrate that is believed to give rise to harmful effect on human health and therefore causes much public concern.In order to finding an effective and practical way to reduce the content of nitrate,the experiment studied the effects of nitrogen levels,nitrogen forms and kinds of fertilizer on the growth,nitrate accumulation and nutrient quality in amaranth through hydroponics and soil pot experiments.The results indicated that:1 In this experiment,the 22mmol·L^-1is the highest in biomass.The content of nitrate increased with the increasing of nitrogen levels,and positive correlation.The content of chlorophyll is 1063.45 mg·g^-1SOD activity and content of MDA declined firstly then increased with the increasing of nitrogen levels,POD activity increased gradually,soluble sugar and the protein decreased.The content of Vc increased firstly then decreased,but the change was not obvious.The content of organic acid also increased firstly then decreased.Results from this experiment shows that optimal N levels 14mmol·L^-1,are essential,from a comprehensive view,for amaranth to achieve high yield,protein and Vc content,and low nitrate content.2.The fresh weight of top and root,leaf length,leaf width and plant height decreased significantly with the increasing of ammonium proportion.There was a significant difference between each treatment.The content of chlorophyll in leaves was the highest when the ratio of nitrate to ammonium was 50:50,but decreased while the content of ammonium was 70 percent.The activity of SOD and POD,the content of MDA is effectec by with the increasing of ammonium proportion.The content of nitrate decreased gradually with increasing of ammonium proportion,and was the highest when supplied pure NO₃^--N.The content of Vc and protein increased with increasing of Hydroponic concentration,and were the highest when supplied pure NH₄⁺-N.The content of organic acid and soluble sugar decreased firstly then increased,and were highest when supplied pure NO₃^--N.The content of organic acid was the lowest when the ratio of nitrate to ammonium was 50:50.70:30.3.Under the condition of this experiment,there was significant difference among all the treatments fertilized.The plant of treatment fertilized urea was the highest,the treatment with compound fertilizer took second place,and the treatment with organic fertilizer was the lowest.There was no significant difference among all treatments of leaf length and leaf width.When supplied organic fertilizer,the yield of amaranth decreased obviously.The content of chlorophyll and the activity of POD and SOD,the content of MDA in all treatments was higher than the control treatment.Vegetables are prone to accumulation of nitrate when supplied compound fertilizer.The content of nitrate was the highest when supplied pure compound fertilizer in amaranth.The content of nitrate in the treatment supplied organic fertilizer was lower than that supplied only urea,but there was no significant difference between them.The order of nitrate content was that compound fertilizer＞urea＞organic fertilizer＞control.All the treatment could raise the content of Vc and soluble sugar.The content of Vc and soluble sugar in the treatment supplied organic fertilizer was higher than that supplied urea and compound fertilizer.The organic fertilizer had not significant effects of control treatment on the content of protein and organic acid,and could improve the qualities better than that supplied inorganic fertilizer.