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Effects of biochar types on properties of sludge-soil mixture and plant growth
Received:September 22, 2022  
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KeyWord:ecological restoration;biochar;sludge utilization;Ruellia simplex
Author NameAffiliationE-mail
LU Jie College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China  
FENG Jiayi College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China  
SHENG Han College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China  
PENG Weixin College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China  
WU Daoming College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China  
ZHANG Xueping Forestry Science Research Institute of Foshan, Foshan 528222, China  
ZENG Shucai College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China sczeng@scau.edu.cn 
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Abstract:
      This study aims to investigate the effects of three biochar types on the physicochemical properties of sludge-soil mixed substrate (mass ratio 1:1) and the growth of garden plants grown in the substrate and explore the potential of biochar application in sludge utilization. A pot experiment was conducted to quantify the effects of three biochar types(added at 4.5% of the substrate mass), including sludge biochar(SB), tree litter biochar(LB), and rice straw biochar(RB), on the physicochemical properties of the substrate, availability of heavy metals, and the growth of Ruellia simplex. Results showed that all the biochar types decreased the bulk density and raised the total porosity and capillary capacity of the substrate compared with that of the control(substrate without biochar addition, CK), with no significant effect on pH. These biochars differently enhanced substrate nutrient levels. SB only significantly increased total P content, whereas LB increased the contents of organic matter, total N, total P, alkaline solubilized N, and available K, and RB promoted the total P, total K, available P, and available K contents. The addition of SB and LB decreased the available P content, while SB reduced the contents of available Cd, Pb, Cu, Zn, and Ni. LB and RB only reduced the available Cu content. These biochars remarkably promoted root biomass and the uptake of N and K by R. simplex, while only SB enhanced the aboveground biomass and the uptake of P by R. simplex. The membership function values showed that the overall effect of the three treatments on substrate improvement and plant growth exhibited the following order:SB > LB > RB > CK. This study shows that the addition of SB, LB, and RB to the sludge-soil mixture effectively improved the substrate quality and promoted the growth of garden plants, with the sludge biochar outperforming the others.