Analysis of nitrogen in 'eco pots' made from Shochu distillation lees

摘要

Japanese whiskey 'shochu' is an alcoholic spirit made mainly from sweet potatoes or cereals, Shochu production, however, results in as much as 621 thousand tons of waste by-product ('distillation lees') every year, of which a fifth is dumped into thesea. As a source of fibre and a potential source of agricultural nitrogen, a technique to make paper (eco paper) from shochu distillation lees has been developed and its application hi agricultural materials is being investigated. In the present study, ~(15)N-labeled eco paper was pasted on the inside walls of black polyethylene pots to determine the behavior of its nitrogen during the growth of komatsuna (Brassica chinensis var. komatsund). Above-ground plant parts absorbed 14.6% and the root system absorbed 1.9% of the total eco paper nitrogen. Just over half (54.2%) of the eco paper nitrogen was retained in the bulk soil. The inorganic nitrogen content of the soil and EC were essentially unchanged over the course of the experiment, suggesting that nitrogen originating from the eco paper is transformed into organic nitrogen by soil microorganisms. Therefore, a longer time is deemed necessary for the plants to absorb all of the nitrogen from the eco pots, indicating that eco pots would be more effective for crops with long cultivation periods, such as fruit and vegetables, than for those with short cultivation periods, such as komatsuna.