STABLE PRODUCTION OF SUMMER SPINACH (SPINACIA OLERACEA L.) IN SOILLESS CULTURE IN THE HIGHLANDS

Differences among cultivars, conditions of nutrient solution, nursing materials, and soilless culture systems were investigated to select suitable cultivar and cultivation methods for stable production of summer spinach in the highlands. The ‘Quinto’ spinach showed the earliest growth and highest yield. For yield increase of summer spinach, optimal solution pH was 6.0, EC was 2.0 dS m^-1, and NH₄-N ratio of nutrient solution was 30%. Growth of spinach in nursing seedlings, at 200-cell-tray filled with nursing soil, was earlier than those grown in urethane sponge and rock-wool. Yield was also 43 to 33% higher than those in urethane sponge and rock-wool. Plant length and yield of spinach in peat filled nutrient film technique (PFNFT) system were 18% longer and 50% higher than those in deep flow technique (DFT) system, respectively. However, changes of solution temperature, pH and EC showed similar pattern with DFT. Therefore, growing ‘Quinto’ cultivar at pH 6.0, EC 2.0 dS m^-1, NH₄-N ratio of 30%, at 200-cell-tray filled with nursing soil, and PFNFT cultivation system, was the best for production of summer spinach in the highlands.