Effects of Different Potassium Concentrations in Nutrient Solution on Growth，Quality and Nutrient Solution Utilization Efficiency of Hydroponic Lettuce

Taking“Flanders”lettuce as research object，five nutrient solution potassium concentrations of 0.6（T1），1.5（T2），2.4（T3），3.0（T4）and 6.0（T5）mmol/L-1 were set up to explore effects of different nutrient solution potassium concentrations on growth，yield，quality，nutrient solution consumption and nutrient solution utilization efficiency of hydroponic lettuce.Results showed that，T4 treatment had the largest leaf area，which increased by 9.33%~65.91% compared with other treatments.Potassium concentration treatment of nutrient solution had no significant effect on SPAD value of lettuce leaves.T4 treatment had the largest crown fresh weight，which increased by 5.91%~145.82%，the root fresh weight of T3 treatment was the largest，which increased by 0.30%~71.88% compared with other treatments.Potassium concentration of nutrient solution was negatively correlated with soluble sugar of lettuce，and it had no significant effect on VC content and no significant effect on lettuce nitrate content.T1 treatment consumed the least nutrient solution，which was 16.01%~35.63% less than other treatments.T5 treatment consumed the most nutrient solution，which was 2.39%~55.48% more than other treatments.T1 treatment has the lowest nutrient solution utilization efficiency，nutrient solution utilization efficiency of T4 treatment was the highest，which was 2.21%~61.89% higher than other treatments.Through relationship between lettuce yield，nutrient solution utilization efficiency and nutrient solution potassium concentration，optimization of nutrient solution potassium concentration was established.When nutrient solution potassium concentration was 3.9 mmol/L，yield of lettuce was the highest，which was 142.03 g/plant；when potassium concentration of nutrient solution was 3.5 mmol/L，nutrient solution utilization efficiency of lettuce was the highest，which was 186.16 g/L.Based on comprehensive considerations，3.7 mmol/L was optimized to be optimum potassium concentration in nutrient solution for hydroponic lettuce.