| In order to realize theprecise control of nutrient solution management for lettuce plant factory cultivation,the effects of nutrient solution controlon growth,yield and quality of lettuce?Lactuca sativa L.?were studied by means of Nurtrient Film Technique?NFT?in the paper.The research includes three parts:The effect of different nutrient solution pH supply on lettuce;The effect of different management methods for nutrient solution concentration on the lettuce from planting to harvest;The effect of the different intermittent supply time of nutrient solution.The experiment were performed in the plant factory locating in Beijing Vegetable Research Center of Beijing Academy of Agriculture and forestry Sciences.In the factory,artificial light NFT cultivation system,light environment for LED light source,the light intensity of 300 mol/m2/s light cycle for 16 h continuous light,were used.Japanese Yamazaki formula and lettuce general trace element formula was selected asnutrient solutionon formula.The lettuce variety was "the father of No.3 lettuce cultivars".The results are as follows.1.Effects of sixnurtrient solution pH?4.0,5.0,6.0,7.0,8.0,9.0?on the growth,yield and quality of lettuce were studied.The results showed that the growth shape,physiological condition and the quality of lettuce were affected by the pH of the nutrient solution during the period from planting to harvest.In the range from4.0 to 9.0 nutrient solutionpH,lettuce can survive,but from a comprehensive point,the most suitable pH is around6.0.As the pH was set at 6.0,number of leaf lettuce is 22.5,plant height of 22.46 cm,on fresh weight of mass 118.47 g,underground fresh weight was 17.42 g,the whole plant fresh weight was 135.83 g,content of chlorophyll 3.86mg·g-1FM,186.25mg·kg-1 for the content of vitamin C,soluble sugar was 38.58g·kg-1,the above content were the highest,which higher than other treatments.However,nitrate content,close to 2119.17mg·kg-1,which was significantly lower than other treatments.When the pH of the nutrient solution was over 6.0,the nitrate content of lettuce had a significantincreased,while the other indexes decreased significantly.2.Effect of different nutrient solution concentrationsat different stageon growth,yield and quality of lettuce were investigated.The seven treatment group were set,respectively,T1?1/2c,1c,2c?,T2?1/2c,2c,1c?,T3?1c,1/2c,2c?,T4?1c,2c,1/2c?,T5?2c,1c,1/2c?,T6?2c,1/2c,1c?and CK?1c,1c,1c?.The results showed that,different concentration management modes had different effects on three different stages of growth and development of lettuce.At its seedling stage,low concentration management mode couldpromote the growth of lettuce,on the contrary,high concentration management mode could inhibit its growth.At its growth and harvest stages,high concentrationmanagement mode significantly promotes the increase of lettuce plant height,leaf length and width.During the harvest period,the biomass accumulation was significantly higher than CK.The T1 and T3 treatments significantly promoted the aboveground and underground lettuce,fresh and dry weight,which were higher than the other treatment.At the same time,the treatment alsoincreasedthe chlorophyll content and root activity in plantssignificantly.Besides,T1 and T3 treatment significantly increased nitrate content,whereas,inhibited the content of soluble sugar,soluble protein and vitamin C in lettuce plants.Under T2 treatment,the content of soluble sugar,soluble protein and vitamin C in lettuce plants had a significant increase,whereas,the nitrate content of lettuce plantswere significantly reduced.It could be inferred that T2 was the most suitable mode to realize the high-effective and high-qualitycultivation inplant factory.3.Effects of NFT cultivation system of different intermittent cyclic fluid feeding time on the growth of lettuce were detected.Four groups were set,CK:as the control groupused as deep-water cultivation,T1: every 10 min for 10 min solution supply,T2:every 20 min for 10 min solution supply,T3: every 30 min for 10 min liquid supply.The results show that,with increasing the nutrition solution interval,height oflettuce plant in the CK group,leaf length and width were decreased significantly.Under the T1 and T2,they had no significant difference.Under T3 treatment,plant height,leaf length,leaf width was significantly lower than that of T1 and T2 treatment,therefore,T3 treatment significantly inhibited the lettuce plants growth.The chlorophyll content and root activity of T1 and T2 treatments were significantly higher than that of T3 treatment,butthe difference between T1 and T2 treatment was not significant.T1 and T2 treatment significantly promoted the increase of chlorophyll content and root activity,while,T3 treatment inhibited the increase of chlorophyll content and root activity.The contents of soluble sugar and vitamin C under theT3 treatmentwere significantly lower than that of T1 and T2,which indicates that T1 and T2 treatment promoted the increase of soluble sugar and vitamin C content in lettuce plants.Under the T3 treatment,nitrate content of lettuce plants were significantly higher than those of T1 and T2,and soluble sugar and vitamin C content in lettuce decreased with the intermittent time of nutrient solution,the content of nitrate increased with nutrient solution intermittent time prolonging,the quality of lettuce decreased,it can be inferred that T3 treatment is not suitable for lettuce cultivation in NFT system. |
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