Study On Nutrient Solution Regulation Model In Tidal Irrigation System Of Multi-layer Lettuce

In order to explore the suitable nutrient solution form of balcony leafy vegetables under tidal irrigation mode,the effects of nutrient solution management mode on the growth,growth and quality of lettuce grown in tidal irrigation system were studied by using tidal irrigation system.According to the morphological index,biomass,nitrate and other quality indexes,the following conclusions are obtained:The results were as follows:(1)the growth and nitrate quality indexes of lettuce were studied under five different nutrient solution of concentrations(0.4s,0.8s,1.2s,1.6s,2.0s).The results showed that under tidal irrigation system,When the EC value was 1.2,the growth index of lettuce could be promoted obviously,and the quality index of lettuce could be improved significantly when the range of EC value between1.2 and 1.6.Therefore,the EC value of 1.2 was suitable for the growth of lettuce.(2)The effects of non-stop liquid(CK)on the indexes of lettuce were tested in the experiment of stopping nutrient solution supply 4,8 and 12 days before harvest.The results showed that stopping nutrient solution for more than 8 days would affect the growth index and vitamin C content of lettuce.When the stopping time was 4 days,it had no significant effects on vitamin C,increased the content of soluble sugar,and significantly reduced the content of nitrate.Therefore,the experiment showed that stopping supplying nutrient solution 4 days before harvest was suitable to reduce the nitrate content of lettuce.(3)under the management of nutrient solution,the experiment was divided into four models: CK indicated constant concentration,T1: "high,low,medium" concentration model,T2: "medium,high and low" concentration model,and T3: "low,medium,high" concentration model.The different nutrient concentration ratios of lettuce at different growth stages were studied.The results showed that the plant height,the number of leaves,the yield per plant and the dry mass of shoot were the largest under the model of "medium high and low" concentration,and the nitrate content was significantly decreased.Therefore,the "medium-high-low" model is moresuitable for the growth of lettuce under multilayer cultivation in tidal irrigation system.(4)In the continuous light supplementation experiment 4 days before harvest,according to various quality indexes,B2 treatment significantly increased the fresh weight,soluble sugar content and vitamin C content of lettuce after 36 hours of continuous illumination,and content of nitrate decreased.Therefore,changing the nutrient solution with EC value of 0.6 before harvest and adding light for 4 days can make lettuce achieves the unity of high quality and low nitrate,thus improving the comprehensive quality of lettuce in water culture.It was an efficient and fast measure to control the quality of vegetables.