Optimal Proportion Selection Of Nutrient Solution And Quality Adjustment Of Hydroponic Lettuce

Plant Factory is a kind of efficient agricultural production method,which relys on modern high-tech agricultural facilities and cultivation techniques.It has high Land productivity, high labor productivity and economic benefits,achieving a balanced annual production of vegetables and other agricultural products, has already become the important means of developing modern agriculture. Hydroponics plant is the leading cultivation techniques of the Plant factory, nutrition nutrient ratio determines the yield and quality of vegetables.Study the influence of different NPK ratio and concentration on growth of hydroponic lettuce, it has important scientific significance and application value for optimal management of the lettuce, reaching the aims of high yield, high quality, low cost production. Chosing the Hong Kong glass brittle leaf lettuce as experiment material,adopted the deep hydroponic method,studied the effects of different concentration of NPK and nutrient solution on hydroponic lettuce growth,quality and the mineral dynamic absorption.(1) When the nitrogen level was 6 mmol·L-1,lettuce can obtain maximum yield,and higher nitrogen levels improved the lettuce quality;Different nitrogen concentration significantly affected the lettuce nitrogen absorption,as nitrogen level increased, phosphorus,potassium,calcium and magnesium absorption efficiency increased first and then decreased,and the nitrogen utilization efficiency linear decreased. (2) When phosphorus level was 0.6 mmol·L-1,lettuce yield gained maximum;and when was 0.4 mmol·L-1,the lettuce quality was the best;as phosphorus level increasing, nitrogen uptake of lettuce had no significant difference,while the phosphorus uptake continually increased,and uptake of potassium reached the peak in the 10 d before harvest,the absorption of calcium,magnesium didn’t change significantly in the whole growth period. (3) When the concentration of potassium level was 3 mmol·L-1,lettuce yield got to the maximum;and when was 4 mmol·L-1,the comprehensive quality of lettuce was best; nitrogen and phosphorus absorption gained the maximum in the 20-30 d after plantpotassium uptake increased as the potassium level increasing,the calcium and magnesium absorption were uniform in the whole growth stage.(4)Relative to the not replacement,the treatment of replacement markedly improved the yield and quality of the lettuce,while the NPK level almost kept the same as the treatment of unchanged nutrient solution when the lettuce yield and quality gained the maximum,the yield difference was not significant,the mineral elements uptake obviously increased,and 30-40 d mineral elements uptake increases continuously.(5) In the quality-control tests of changing the concentration of the nutrient solution at the last of the growth,as the concentration increased,the yield increasd accordingly,and reached the maximum in the 2 times fomula;when the concentration was 0 times,the lettuce gained the lowest nitrate,highest vitamin C and soluble sugar,when the concentration was 0.5 times,the lettuce gained the highest soluble protein,Chlorophyll a and Chlorophyll b.(6) In the quality-control tests of changing the concentration of the nutrient solution at the last of the growth,the sequence stages which influenced the lettuce yield were 30～40 d、20-30d、0-20d after planting,at last,got the optimization of production plan,that was in the stage of 30～40 d,20～30 d,0～20 d,the corresponding nutrient solution was ltimes,ltimes,ltimes,orl times,0.75 times,0.5 times.