Changes in chemical characteristics of drainage solution as influenced by years of root media use in successive hydroponic cultivations of ‘seolhyang’ strawberries

Abstract

Changes in the pH, electrical conductivity (EC), and concentrations of essential nutrients have to be analyzed to enable reuse of the drainage solution (DS) in closed hydroponic cultivation of a crop because the chemical characteristics (CC) of drainage vary in relation to the kind of crop grown and the root media used. The objective of this research was to investigate changes in the CC of DS during cultivation of ‘Seolhyang’ strawberries. The root medium is composed of coir dust, peat moss, and perlite in the ratio 6:2:2 (v/v/v), and the composition of the nutrient solution applied for crop cultivation is N, P, K, Ca, and Mg at 15, 5, 7, 6, and 2 mg·L-1, respectively. The changes in the CC of the DS as well as the growth, yield, and fruit quality were investigated in relation to the number of years the root media used. The pH of the DS decreased as the number of years of root medium usage increased. The ECs of DS in all treatments were in the range of 0.8 to 1.5 dS·m-1 during the growing season and tended to rise as the number of years of usage in the root medium increased. The concentrations of NO3 and Ca in the DS ranged from 200 to 600 mg·L-1 and 52 to 176 mg·L-1, respectively. The K concentration in the DS was in the range of 104 to 221 mg·kg-1 in all treatments during the growing season. The concentrations of P and Mg in the DS were 15 to 60 mg·L-1 and 18 to 48 mg·L-1, respectively. As the number of years of root media usage increased, the concentrations of NO3, P, Ca, and Mg tended to rise, whereas that of K tended to decrease. The different treatments with varying number of years of root medium usage did not lead to significant differences in plant growth, tissue nutrient content, budding and flowering date, and total yield. The results from this research, the changes in nutrient composition of the DS and their effect on tissue nutrient content, can be used to modify the nutrient composition in the DS when the solution is reused in closed hydroponic cultivation of ‘Seolhyang’ strawberries.