The possibility of using sintered materials from sludge in tagonoura bay as plant growth medium (1) element analysis of sintered materials and preliminary plant growth experiment

摘要

Sintered materials from sludge dredged from Tagonoura bay were used as plant growth medium. The materials were sintered at temperatures of 900-1050 deg C (LT medium), 1050-1120 deg C (MT medium) and 1120-1160 deg C (HT medium). Trace element analysis of the elutions of sintered materials showed that the concentrations of elements tended to increase with decreased sintering temperature. Their concentrations were less than the allowable levels except for vanadium, which showed concentration of about 2 #mu#g/g in LT medium. In the preliminary plant growth experiment, lettuce (Lactuca sativa L. cv. Okayama) was grown in LT, MT and HT media. Nutrient solutions passing through the three sintered media had high pH (about 9) 4 days after the beginning of the experiment, followed by a pH of about 7 measured 11 and 18 days after the beginning of the experiment. The dry and fresh weights and leaf area of lettuce were lowest for plants grown in LT medium. Lettuce growth in MT and HT media were also delayed compared with that in rock wool medium. These low growth rates of lettuce grown in sintered media might be related to the trace elements eluting from the media. Sintering technology should be developed to decrease the trace elements eluting from sintered materials and further research is needed to utilize the sintered materials as plant growth medium.