Study On Nutritional Effect Of Organic-N On Lettuce And Dissolved Oxygen Techniques In Hydroponics

In this experiment, We have studied the nutritional effect of organic-Non the lettuce fertilization ways of the amino acid sterilization ways of the nutrient solution and techniques of dissolved oxygen. The conclusions are as follows: The first: We studied the effect of different mixture of urea and amino acids as partial (20%) replacing nitrate of solution on nitrate content and quality of lettuce in hydroponics. Five treatments were done 12d before harvest. Compared to contrast treatment of total inorganic-N, the treatments of partial replacement of nitrate by organic-N can improve the production and the quality of the lettuce obviously and can reduce the nitrate content of the lettuce especially. The effect of two treatments of partial replacement of nitrate by Gly single and by Urea single on the growth and the total FW and DW of lettuce are better than other treatments. The mixture of Gly Iso Pro L-Ala Glu L-Arg with equal content had the best effect in elevating the physiological index and improving the quality of lettuce. The mixture of amino acids can reduce the nitrate content obviously. Compared to contrast treatment of total inorganic-N, The nitrate content of lettuce of the treatment with the mixture amino acids can reduce 24.14%, the two treatments of partial replacement of nitrate by Gly single and by urea single have the same effect of reducing nitrate content.The second: We studied the effect of different fertilization ways of amino acid and the sterilization ways of nutrient solution on the production and the quality of the lettuce in hydroponics when the 20% nitrate of the solution was replaced by mixed amino acid. The result are as follows: the way of fertilization 1 time is prior to the way of fertilization several times when the nutrient solution was not been sterilized; But, the way of fertilization several times can decreased the nitrate content of the lettuce than the way of fertilization 1 time. The production and the quality of the lettuce in sterilized nutrient solution will be higher than that of the lettuce in the fertilized nutrient solution; the way of sterilization by heating is prior to the way of sterilization by releasing ozone. The difference of the effect of the two ways of sterilization by heating and releasing ozone on the lettuce is not evident.The third: We studied the techniques of dissolved oxygen in DFT about lettuce when we take total inorganic-N as nitrate source, the conclusions are as follows: The density of the dissolved oxygen would not increase when the solution was circulating for 40 minutes by a water pump with the power of 20W; The oxygen consumption of the lettuce in the day was more than that in the evening, Even the oxygen consumption in the evening can be neglected; The larger the leaf area is , The larger the oxygen consumption velocity is ; The interval time of the circulating with the water pump=(7.9mg/L-4.5ml/L)*the volume of the solution /(the oxygen consumption velocity per plant *the number of the lettuce per group). Among them,the oxygen consumption date per plant can be calculated according to the regression equation of the leaf area and the oxygen consumption velocity: y=0.009X+0.1011 (R2=0.9966), (X represents leaf area in different period)...