Abstract: The effect of sludge-based mixed substrates (SBMSs) on the growth and flowering of Angelonia salicariifolia (ASA) was studied with a pot experimental method. The growth suitability of ASA to these substrates was then evaluated using entropy weight coefficient and TOPSIS method. The sludge was composted 60 days prior to mixing and potting with peats and sands at different ratios. Our results showed that SBMSs had lower values in bulk density and EC, but higher values in pH and nutrient content than latosolic red soil (CK) in the study region. The ASA in the differently mixed substrates all grew better than in the soil, with the increases in heights, branchlet numbers, fresh and dry weights by 29%-61%, 27%-67%, 17%-88% and 4%-50%, respectively. In addition, the first flowering of ASA in the SBMSs blossomed 2-16 days earlier, their flower numbers in the fullbloom stage increased by 49%-220%, the flowering duration prolonged 8-22 days, and the malformation rate of flowers decreased by 1%-5%. The absorption of nitrogen, phosphorus and potassium by ASA showed a significant increase over CK. All the 7 substrates in this study were suitable for ASA growth. Entropy weight coefficient and TOPSIS evaluation indicated that SBMSs with the ratio of 5∶3∶2 of sludge compost to peat to sand was most suitable for the growth of this plant, and the sludge compost alone was relatively less suitable, but still better than the soil (CK). Therefore, sewage sludge compost can improve flower quality and plant growth with a reduce cost, which is a feasible and effective way for sewage sludge reuse and disposal.

Key words: photosynthetic pigment, photosynthetic characteristics, Phragmites australis, chloroplast ultrastructure, UV-B radiation