[Effects of sewage sludge compost on the growth and element uptake of Neolamarckia cadamba seedlings].
Sewage sludge compost (SSC) is rich in organic matter and nutrient elements indispensable to plant growth. Utilizing SSC as seedling growing substrate is generally recognized as a new ecological method for utilization of sewage sludge. We investigated impacts of SSC treatments including 0% (CK), 25% (T1), 50% (T2), 75% (T3), and 100% (T4) on the growth and nutrient uptake of Neolamarckia cadamba seedlings in a 7-month pot experiment. The changes in element contents in substrate after pot experiment were also addressed. Results showed the SSC treatments had significant impacts on the growth of N. cadamba seedlings. The seedlings in T4 treatment grew abnormally and all died in two weeks after transplanting. Seedling height, ground diameter and biomass in T1, T2 and T3 treatments were significantly higher than CK, with those in T2 being the best among all treatments. Seedlings in T2 and T3 treatments took up significantly more N, P, K, Cu, Zn, Pb and Cd, while those in T1 treatment absorbed significantly more N and Pb than CK. The heavy metal uptake amount of each treatment exhibited the order of Zn＞Cu＞Pb＞Cd. At the end of the pot experiment, the contents of organic matter, N, P and K in growing substrate were still relatively high, and a certain portion of heavy metals still remained in the substrate, but with lower contents than the standards set for agricultural usage-oriented sewage sludge, indicating that the post-experiment substrate may be reused.