Effection Of Nitrogen Fertilizer And Water Retaining Agent On Growth And Relavant Enzyme Activities Of Compound Sand Culture Tomato

In recent years,with the increasing demand for tomato export,the compound sand culture tomato industry has developed rapidly.Compound sand culture has the advantages of avoiding root continuous cropping obstacles,less diseases and insect pests,and easy to obtain high-yield and high-quality products,but as a substrate,it has some disadvantages,such as weak buffer capacity,poor performance of water and fertilizer conservation and so on.In order to achieve the goal of high yield and high income,farmers blindly open the high nitrogen model,the emergence of water-retaining agent can make up for the poor water retention of sand and effectively alleviate the damage caused by short-term water shortage.Therefore,the study on the amount of nitrogen and water-retaining agent is of great significance to the application of compound sand tomato.In order to select the best application amount of water-retaining agent under the condition of appropriate amount of nitrogen fertilizer,under the condition of sand:coconut bran:chicken manure=2:1:1(volume ratio),firstly,the best treatment of different nitrogen application rate was selected,and then,on the basis of the optimum nitrogen application rate,the best treatment of different water-retaining agent application rate was selected,the physiological mechanism of tomato was discussed,and the reasonable nitrogen application rate and water-retaining agent application management system of compound sandy tomato cultivation were constructed.In this study,nitrogen application rate and water-retaining agent application rate were used as single factors to explore the effects of nitrogen application rate on nitrogen metabolism enzyme activity,photosynthetic characteristics,yield and quality of tomato.Then,the effects of water-retaining agent application rate on antioxidant enzyme activity,photosynthetic characteristics,yield and quality of tomato were studied.(1)Appropriate amount of nitrogen application can promote the growth of tomato plants,increase the activity of nitrogen metabolic enzymes in leaves,enhance the photosynthetic characteristics of leaves,and then improve fruit quality and yield.Compared with the control,the plant height,stem diameter and leaf area of 285 kg/hm2 significantly increased by 3.81%,8.71%and 24.19%respectively.The total chlorophyll content,nitrate reductase activity and glutamine synthetase activity were the highest in the full fruit stage,of which were 13.14%,42.79%and 182.93%higher than those of the control.With the increase of nitrogen application rate,the net photosynthetic rate and transpiration rate of tomato increased at first and then decreased,and the net photosynthetic rate of 285 kg/hm2 treatment increased by 48.89%compared with the control.The transpiration rate of 428 kg/hm2 treatment increased by 28.10%compared with the control.The lycopene content,soluble protein content,soluble sugar content,soluble solids content,sugar-acid ratio and yield of 285 kg/hm2 treatment increased by 364.35%,33.33%,21.43%,17.98%,20.53%and 66.92%428 kg/hm2 respectively compared with the control.Vitamin C content,soluble protein content,soluble sugar content and soluble solids content were the highest in fruit quality.Compared with the control,it increased by 70.33%,66.67%,25.00%and 27.25%respectively,and its yield was also the highest,with an increase of 66.92%.Considering the growth and physiological characteristics,fruit quality and yield of tomato,it can be inferred that the best nitrogen application rate of compound sand culture tomato should be between 285 kg/hm2～428 kg/hm2.(2)Under the same amount of nitrogen application,the combination of nitrogen fertilizer and waterretaining agent increased plant height,stem diameter,number of true leaves,SOD,CAT,POD,APX enzyme activity,net photosynthetic rate,yield and quality of tomato plant.When the dosage of water-retaining agent was 180 kg/hm2,the stem diameter of tomato was the thickest,the length of the first Internode was the shortest,and the plant height and leaf area of tomato were the largest when treated with 135 kg/hm2.The activities of POD and APX in 13 5 kg/hm2 treatment were the highest,and the activities of SOD and CAT in 180 kg/hm2 treatment were the highest.With the increase of the amount of water-retaining agent,proline reached the lowest value in 135 kg/hm2 treatment,and the content of soluble protein and soluble sugar in tomato leaves treated with 180 kg/hm2 was the highest.With the increase of the application amount of waterretaining agent,the contents of MDA and O2·-decreased gradually,and the net photosynthetic rate and transpiration rate of tomato increased at first and then decreased.When the dosage of water-retaining agent was 135 kg/hm2,the contents of lycopene,vitamin C,soluble protein,soluble sugar and soluble solids in tomato fruit were the highest.Considering the drought resistance,fruit quality and yield of tomato,which was concluded that 135 kg/hm2 was the best application rate of water-retaining agent for compound sand-cultured tomato.