2019 ASHS Annual Conference

We investigated how to reduce nitrate contents in leafy vegetables grown in plant factor conditions. It is well-known that excess nitrate has sometimes bad influence human health. It is noteworthy that it is relatively easy to control the concentration of nutrient solution at hydroponic culture. However, when plants were grown under low concentration of nitrate condition, it became light green and had no market value. Thus, to reduce the contents of nitrate in leafy vegetable, and keep fresh green, we investigated how to grow leaf lettuce (Lactuca sativa L. s. var. crispa) under controlled culture conditions (plant factory).
At five days before cultivation, we changed the nutrient solution to water, or cut the half amount of root, or cooled nutrient solution, and analyze the contents of nitrate in the lettuces. Also, we checked SPAD value for measuring concentrations of chlorophyll. As a result, we were able to reduce nitrate contents without decreasing SPAD value, by changing nutrient solution to water. This technique might be efficient for growing low nitrate contents of leaf lettuce in plant factories.