| The main environment of hydroponic plants is light and nutrient solution,light providing energy sources for plants,and nutrient solution providing essential nutrients for plants.Therefore,the light and nutrient solution are of great significance to the development of hydroponics.Biogas liquid contains a large amount of nutrients needed for vegetable growth and is a renewable resource,which can improve the effective utilization of resources.Therefore,biogas liquid is used to partly replace inorganic nutrient liquid to form compound nutrient solution for vegetable cultivation.The experiment of lettuce was carried out under the condition of combination of light intensity and nutrient solution,including light intensity,inorganic nutrient solution and compound nutrient solution,using lettuce as test material and sham formula as basic nutrient solution.Combine.The compound nutrient solution is based on the formula of sham,replacing the 40%.The effects of different combinations on the growth,quality,mineral element absorption,photosynthesis and chlorophyll fluorescence characteristics of hydroponically cultured lettuce were obtained as follows:(1)The experimental study on the combination of light intensity and inorganic nutrient solution showed that the yield,quality,water use efficiency and nutrient use efficiency of lettuce were obviously improved by increasing the light intensity or nutrient concentration.The change of fresh quality,chlorophyll content and nutrient absorption and utilization rate of lettuce increased first and then decreased with the increase of light intensity.The content of soluble sugar and soluble protein increased with the increase of light intensity and increased first and then decreased with the increase of concentration of nutrient solution;nitrate decreased with the intensity of light intensity.The content of chlorophyll was high,the net photosynthetic rate was the highest,the photochemical efficiency was higher,the fluorescence was less,heat dissipation was less,and the heat dissipation was low,with the increase of light intensity.The best combination of the 1.0 times nutrient solution concentration and 250umol/m~2s light intensity treatment is the best combination of water culture in 12 combinations.(2)The experimental study shows that adding biogas liquid can improve the content of VC in lettuce and increase the content of lettuce from the combination of light intensity and organic and inorganic compound nutrient solution.The nutrient utilization efficiency of lettuce could also improve the appearance of lettuce.Nitrate content decreased with the increase of light intensity,increased with the increase of the concentration of compound nutrient solution,and the light intensity and the concentration of compound nutrient solution were positively correlated with the content of soluble sugar;the light intensity was certain,the concentration of soluble protein increased first with the increase of the concentration of compound nutrient solution.The content of VC content increased first and then decreased with the increase of light intensity or the concentration of compound nutrient solution.When the concentration of compound nutrient solution was 0.6 times,the demand for water in the lettuce was the largest,and with the increase of light intensity,the trend was first and then decreased.The maximum light intensity was 250umol/m~2s,nitrogen,phosphorus and magnesium.The utilization efficiency of element utilization efficiency increased first and then decreased with the intensities of light intensity.When 0.6 times of nutrient solution concentration and 250umol/m~2s light intensity were treated,the utilization efficiency of phosphorus,potassium and magnesium in lettuce was the highest.The utilization efficiency of mineral elements and the fresh leaf weight of lettuce were the same,the higher the water use efficiency and the efficiency of nutrient utilization were.The higher and the yield accumulation effect,the better.Considering the combination of 0.6 times the combination of organic and inorganic compound nutrient solution and 250umol/m~2s light intensity,the yield of lettuce,the use efficiency and the water use efficiency are optimal.Compared with the inorganic nutrient solution,the content of VC in lettuce is improved to a certain extent,and the utilization of mineral elements is also improved obviously.High concentration of biogas solution significantly reduced the yield of lettuce,indicating that high concentration of biogas liquid is not conducive to the accumulation of dry matter in lettuce.(3)The principal component analysis of the element utilization,yield and quality of inorganic,organic and inorganic compound nutrient solution in Hydroponic Lettuce were analyzed.The optimum light intensity and the combination of inorganic nutrient solution were calculated.The combination of 1.0 times the concentration of nutrient solution and the intensity of250umol/m~2s light,the combination of the optimal light intensity and the organic and inorganic compound nutrient solution is the combination of 0.6 times the concentration of nutrient solution and the intensity of 250umol/m~2s light. |
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