Microbial activity and dissolved organic matter dynamics in the soils are affected by salinity and sodicity

A laboratory incubation experiment was conducted to assess changes in microbial activity, dissolved organic matter (DOM) and nutrients dynamics in response to salinity and sodicity. We hypothesised that salinity would decrease microbial activity due to osmotic stress, whereas sodicity would increase microbial activity as a result of increased organic matter solubility. A non-saline non-sodic soil was repeatedly leached using a combination of 1M NaCl and 1M CaCl2 solutions to reach EC1:5 0.4, 1.2, 2.5 and 4.0 dS/m combined with SAR < 3, 10 and 20. Two percent finely ground wheat straw residue was added as an amendment. The results indicate that cumulative respiration on day 64 was more strongly affected by EC than SAR. Cumulative respiration was highest at low EC1:5 (0.4) and high SAR (20) and lowest at high EC1:5 (4.0) and high SAR (20). Increasing salinity adversely affected the microbial activity in the soil, whereas increased the microbial activity in response to sodicity was only observed at EC1:5 (0.4).M. S. Mavi, P. Marschner, D. J. Chittleborough and J. W. Co