Drying and wetting in saline and saline-sodic soils—effects on microbial activity, biomass and dissolved organic carbon
There are few studies on the interactive effect of salinity and sodicity in soils exposed to drying and wetting cycles. We conducted a study to assess the impact of multiple drying and wetting on microbial respiration, dissolved organic carbon and microbial biomass in saline and saline-sodic soils.
Different levels of salinity (EC1:5 1.0 or 2.5) and sodicity (SAR < 3 or 20) were induced by adding NaCl and CaCl2 to a non-saline/non-sodic soil. Finely ground wheat straw residue was added at 20 g kg−1 as substrate to stimulate microbial activity. The constant moist (CM) treatment was kept at optimum moisture content for the length of the experiment. The drying and rewetting (DW) treatments consisted of 1 to 3 DW cycles; each DW cycle consisted of 1 week drying after which they were rewet to optimum moisture and then maintained moist for 1 week.
Drying reduced respiration more strongly at EC2.5 than with EC1.0. Rewetting of dry soils produced a flush in respiration which was greatest in the soils without salt addition and smallest at high salinity (EC2.5) suggesting better substrate utilisation by microbes in soils without added salts. After three DW events, cumulative respiration was significantly increased by DW compared to CM, being 24% higher at EC1.0 and 16% higher at EC2.5 indicating that high respiration rates after rewetting may compensate for the low respiration rates during the dry phase. The respiration rate per unit MBC was lower at EC2.5 than at EC1.0. Further, the size of the flush in respiration upon rewetting decreased with each ensuing DW cycle being 50–70% lower in the third DW cycle than the first.
Both salinity and sodicity alter the effect of drying and rewetting on soil carbon dynamics compared to non-saline soils.
KeywordsDissolved organic C Drying and wetting Microbial activity Microbial biomass Salinity Sodicity
The authors thank Harsimranjeet Mavi, Colin Rivers and John Gouzos for the technical and analytical support. This project is being funded by an Endeavour scholarship from The University of Adelaide to the senior author and by Future Farm Industries, CRC, Australia.
- Anderson JM, Ingram JSL (1993) Tropical soil biology and fertility. CAB International, WallingfordGoogle Scholar
- Blake GR (1965) Bulk density. In: Black CA, Evans DD, Ensminger LE, White JL, Clark FE (eds) Methods of soil analysis. Part 1. Physical and mineralogical properties. American Society of Agronomy, Madison, pp 374–390Google Scholar
- Brady NC, Weil RR (2002) The nature and properties of soils. Pearson Education Ltd, New JerseyGoogle Scholar
- Chowdhury N, Yan N, Islam MN, Marschner P (2011) The extent of drying influences the flush of respiration after rewetting in non-saline and saline soils. Soil Biol Biochem. Accepted for publication Google Scholar
- Harris RF (1980) Effect of water potential on microbial growth and activity. Special Edition #9. In: Parr JF, Gardner WR (eds) Water potential relations in soil microbiology. Soil Science Society of America, Madison, pp 23–95Google Scholar
- Keren R (2000) Salinity. In: Sumner ME (ed) Handbook of soil science. CRC Press, Boca Raton, pp 3–25Google Scholar
- Martinez-Beltran J, Manzur CL (2005) Overview of salinity problems in the world and FAO strategies to address the problem: Proceedings of the international salinity forum. Riverside, California, April 2005, pp 311–313Google Scholar
- Meehl GA, Stocker TF, Collins WD et al (eds) (2007) Global Climate projections. In: Climate change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental panel on Climate change. Cambridge University press, Cambridge, UK, pp 747–845Google Scholar
- Rayment G, Higginson F (1992) Australian laboratory handbook of soil and water chemical methods. Inkata Press, SydneyGoogle Scholar
- US Salinity Laboratory Staff (1954) Diagnosis and improvement of saline and alkali soils, vol No. 60. USDA Handbook, US Government Printing Office, Washington DCGoogle Scholar
- Shainberg I, Letey J (1984) Response of soils to sodic and saline conditions. Hilgardia 52(2):1–57Google Scholar
- Sommers LE, Gilmour CM, Wildung RE, Beck SM (1981) The effect of water potential on decomposition process in soil. In: Parr JE, Gardner WR, Elliot LF (eds) Water potential relation in soil microbiology. Soil Science Society of America, MadisonGoogle Scholar
- Voroney RP (2007) The soil habitat. Soil microbiology, ecology and biochemistry. Elsevier, OxfordGoogle Scholar