Pedosphere 25(2): 177--185, 2015
ISSN 1002-0160/CN 32-1315/P
©2015 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Responses of soil microbial activity and biomass to salinity after repeated additions of plant residues |
B. ELMAJDOUB1,2 , and P. MARSCHNER1 |
1School of Agriculture, Food and Wine, The Waite Research Institute, The University of Adelaide, Adelaide SA 5005 (Australia)
2Biotechnology Research Centre, P.O. Box 30313, Tripoli (Libya) |
| ABSTRACT |
| Microbial adaptation to salinity can be achieved through synthesis of organic osmolytes, which requires high amounts of energy; however, a single addition of plant residues can only temporarily improve energy supply to soil microbes. Therefore, a laboratory incubation experiment was conducted to evaluate the responses of soil microbes to increasing salinity with repeated additions of plant residues using a loamy sand soil with an electrical conductivity in saturated paste extract (ECe) of 0.6 dS m-1. The soil was kept non-saline or salinized by adding different amounts of NaCl to achieve ECe of 12.5, 25.0 and 50.0 dS m-1. The non-saline soil and the saline soils were amended with finely ground pea residues at two rates equivalent to 3.9 and 7.8 g C kg-1 soil on days 0, 15 and 29. The soils receiving no residues were included as a control. Cumulative respiration per g C added over 2 weeks after each residue addition was always greater at 3.9 than 7.8 g C kg-1 soil and higher in the non-saline soil than in the saline soils. In the saline soils, the cumulative respiration per g C added was higher after the second and third additions than after the first addition except with 3.9 g C kg-1 at ECe of 50 dS m-1. Though with the same amount of C added (7.8 g C kg-1), salinity reduced soil respiration to a lesser extent when 3.9 g C kg-1 was added twice compared to a single addition of 7.8 g C kg-1. After the third residue addition, the microbial biomass C concentration was significantly lower in the soils with ECe of 25 and 50 dS m-1 than in the non-saline soil at 3.9 g C kg-1, but only in the soil with ECe of 50 dS m-1 at 7.8 g C kg-1. We concluded that repeated residue additions increased the adaptation of soil microbial community to salinity, which was likely due to high C availability providing microbes with the energy needed for synthesis of organic osmolytes. |
| Key Words: C availability, electrical conductivity, microbial biomass C, microbial community, respiration, saline soil |
| Citation: Elmajdoub, B. and Marschner, P. 2015. Responses of soil microbial activity and biomass to salinity after repeated additions of plant residues. Pedosphere. 25(2): 177-185. |
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