Study On Hydroponic Technology Of Lettuce

Selection of seedling substrates and nutritional solutions ofhydroponic lettuce; optimization of nutritional concentration; experiment of fertilizer substitution partly of nutritional solutions; effects of different Nitrogeous forms and NO3- to NH+4 ratio on Nitrate content in lettuce are studied. The results are summarized as follows: l)Vermiculite, rockwool, sponge, flowermud are studied as the hypodronic substrates. The result of vermiculite seedling is the best. The result of rockwool seedling is second. But in consideration of the application of hydroponic production, rockwool is thought to be the most suitable for hydroponic seedling. 2)Four kinds of nutritional solutions A, B, C, Dare selected in this experiment. Solutions B and D are thought to be more suitable for hydroponic production. 3)The optimization of nutritional concentration is based on solutions B and D. Seven treatments of gradient EC=1.5, 2.0, 2.5, 3.0,3.5, 4.0, 4.5 are set up to look for the most suitable concentration of solutions B and D. Treatment EC=3.0 is the most suitable concentration of solutions B and D; treatment EC=3.5 is the more suitable concentration of solution D. 4)On base of Nitrogen concentration 151.1 g/t of solution D, six kinds of different solutions NO3- â–¡NH+4=80â–¡ 20 ,70â–¡30, 60â–¡40, 50â–¡50, urea substitutable for NO3- and solution D (CK) are set up in the experiment of fertilizer substitution partly of nutritional solutions. The result is treatment NO3~-N: NH4+-N =70 : 30 is the best.; treatment NO3'-N: NH4+-N =80020 is better. Fitful NH/-N is better than urea. 5) On base of Nitrogen concentration 151.1 g/t of solution D, six kinds of different solutions NO3-N: NH4-N=90: 10, 80: 20, 70: 30; NO3-N: CO(NH2)2=75: 25, 50: 50, 25: 75 are set up in the experiment of effects of different Nitrogeous forms and NO3- to NH+4 ratio on Nitrate content. The result is only the Nitrate content of treatment NO3-N: CO(NH2)2=25: 75 is able to be not beyond standard 2, other indexes are good too. So this treatment is thought to be suitable for application in the production.