Abstract
Establishment of an experimental system composed of plants, animals and humans, in which materials are circulated in a closed loop, is underway using the Closed Ecology Experiment Facilities (CEEF), for investigation of carbon dynamics. The plant cultivation system takes roles of supplying food, oxygen and clean water to, and scrubbing carbon dioxide from, humans and animals in the experimental system. A hydro-culture technique is used for the plant culture system. It is necessary to circulate nutrient solution in the plant cultivation system in order to circulate water in the CEEF. To obtain data on carbon transfer using the CEEF, it is necessary to establish a steady plant cultivation system. In the system, water transpired from the plants are collected as condensate, and it is reused for replenishment of water in each plant cultivation bed. In order to circulate water, not only transpired water but also waste nutrient solution need to be regenerated and reused. Main crops in the plant cultivation system include rice, soybean and peanut. Some elements such as copper and zinc were accumulated, but total organic carbon (TOC) did not increase in the nutrient solution, when the nutrient solution was circulated. This study compared the soybean yield cultivated using the circulated nutrient solution (circulating system) with that cultivated using newly produced solution (non-circulating system). Result of this study showed that circulation of nutrient solution did not decrease soybean production compared to that without circulation of nutrient solution. This research was performed under contract with the Aomori Prefectural Government, Japan.
