Study On The Effects Of Different Environments On The Occurrence And Quality Of Dry Heartburn Of Hydroponic Lettuce Under Facility Cultivation

Plant factory is the advanced stage of facility cultivation.Its environment can be automatically controlled by manual or computer to achieve the optimal growth environment for cultivated crops,so as to achieve the purpose of high-quality cultivation.The tipburn disease of lettuce is a common physiological disease of lettuce in plant factories.Its incidence rate is much higher than that of open field cultivation.The disease often occurs in the heart leaves of lettuce.Brown spots begin to appear on the edge of the diseased leaves,and then develop into brown spots.In severe cases,the heart leaves of lettuce rot,which seriously affects the quality of lettuce and reduces the economic benefits of plant factories.Therefore,in order to improve the quality of lettuce and reduce the incidence of tipburn,the common lettuce varieties ’ Lvya ’ and ’Italy ’ in Beijing were used as test materials in this experiment.The effects of different environments and cultivation methods on the quality of lettuce and the incidence of tipburn under facility cultivation were explored from the aspects of light,nutrient solution concentration and foliar fertilizer,in order to lay a theoretical foundation for the high-quality production of lettuce under facility cultivation.The results of this experiment are as follows :(1)Under the treatment of different light quality and light ratio,it was found that the net photosynthetic rate was the highest and the dry heart rate was the lowest under the treatment of red and blue light ratio of 3 : 1,while the dry heart rate of lettuce under blue light treatment was the highest.The growth status of lettuce was also better than that of monochromatic light treatment under red and blue light mixed treatment.The yield of two varieties of lettuce reached the highest under the treatment of red and blue light ratio of 5 : 1.At the same time,the nutritional quality of lettuce did not decrease significantly under the treatment of red and blue light ratio of 3 : 1,and the red and blue light ratio of3 : 1 was the most suitable light quality treatment for lettuce facility cultivation.(2)In this experiment,by adjusting the amount of calcium nitrate and ammonium sulfate in the hydroponic nutrient solution,the calcium ion concentration of the hydroponic nutrient solution and the ratio of ammonia to nitrate of nitrogen were changed.The results showed that after adjusting the calcium ion concentration in the hydroponic nutrient solution,it was found that the disease of lettuce dry heartburn increased first and then decreased with the increase of calcium ion concentration in the nutrient solution.When the calcium ion concentration in the nutrient solution was 2.4 mmol / L,the disease of dry heartburn decreased to the lowest,and the yield,root activity and soluble sugar content of lettuce were the highest,while the Vc content and soluble protein content were not seriously affected.In general,it is the most suitable formula for facility cultivation.(3)Foliar spraying of calcium chloride is an effective cultivation measure to supplement calcium in leaves.After spraying different concentrations of calcium chloride solution on leaves,it was found that the concentration of calcium ion in heart leaves increased with the increase of spraying concentration,but the trend of increase gradually slowed down.The condition of dry heartburn also decreased with the increase of the concentration of calcium chloride solution,and the onset time was delayed.Under the treatment of 0.5 % concentration of calcium chloride solution,the yield of lettuce reached the highest,and then the yield decreased with the increase of concentration,while the nutritional quality was the best under the treatment of 0.5 % concentration of calcium chloride solution.At the same time,some physiological indexes also showed a trend of increasing first and then decreasing with the increase of calcium chloride spraying concentration,and reached the highest at 0.5 % concentration.The treatment of lettuce with 0.5 % concentration of calcium chloride solution under facility cultivation is an effective cultivation measure to prevent dry heartburn.