Comparative analysis of water purification efficiency of Oryza sativa L. and Cyperus alternifolius L. in the floating culture system

摘要

A study was made of the nitrogen absorption of rice and C. alternifolius grown in the floating culture system to examine the water purification efficiency of these species. The seedlings were transplanted onto floating boards placed on a water pooland grown with or without the application of a slow-release NPK fertilizer for about three months. C. alternifolius showed higher rates of nitrogen absorption from water (DELTANw) with and without fertilizer during the middle and late growth periods, resulting in higher water purification efficiency. Water purification efficiency was further improved with fertilizer application at transplanting because the fertilizer application increased both the root weight and nitrogen absorption rate on a unit rootweight basis. Rice had a negative effect on water purification when fertilizer was applied, although dry matter production was increased. The difference in nitrogen absorption and response to fertilizer application between rice and C. alternifolius was also confirmed by a 15N tracer experiment. A positive significant relationship was detected between DELTANw and the dry weight of roots in the non-fertilized plants of C. alternifolius.