Analysis of nutrient contents and change rate of the drainage solution in hydroponics of strawberries

Analysis of nutrient contents and drainage rate in a plastic house was undertaken to improve hydroponics of strawberries by recycling the solution more efficiently. The experiment was conducted in January when the air temperature was the lowest. When each plant was given 150 mL of irrigation nutrients daily, the regression coefficient of the drainage rate among relative humidity, intensity of solar radiation and air temperature were r²=0.80 (regression coefficient between the drainage rate and the relative humidity), r²=0.75 (regression coefficient between the drainage rate and the intensity of solar radiation) and r²=0.70 (regression coefficient between the drainage rate and the air temperature). It was concluded that the relative humidity is the factor affecting the drainage rate of the residual solution the most. When the pH and electrical conductivity (EC) of the nutrient solution were 6.5 and 1.2 (dS m^-1) in January, the pH and EC of the drainage solution were 7.0-6.6 and 1.2-1.4 (dS m^-1), respectively. It was observed that when drainage percentage increased, EC decreased (r²=0.65). The pH also increased when drainage percentage increased (r²=0.40). However, the statistical significance was low which meant that drainage percentage affected EC more than it affects the pH. When the nutrients mole concentration rate (NO₃-N:P:K:Ca:Mg = 11.4:1.8:6.8:3.5: 1.5 mM) were supplied, the nutrient mole concentration rate of the drainage solution was NO₃-N:P:K:Ca:Mg = 7.1:1.6:4.6:3.5:1.5 mM. Difference in NO₃-N concentration of influx and efflux solution was the greatest, followed by K and P, respectively.