Journal Article

Is CO₂ evolution in saline soils affected by an osmotic effect and calcium carbonate

Chittleborough, David, Setia, Raj, Baldock, Jeff, Marschner, Petra

2010

Overview

Salt-affected soils are widespread, particularly in arid climates, but information on nutrient dynamics and carbon dioxide (CO₂) efflux from salt-affected soils is scarce. Four laboratory incubation experiments were conducted with three soils. To determine the influence of calcium carbonate (CaCO₃) on respiration in saline and non-saline soils, a loamy sand (6.3% clay) was left unamended or amended with NaCl to obtain an electrical conductivity (EC) of 1.0 dS m⁻¹ in a 1:5 soil/water extract. Powdered CaCO₃ at rates of 0%, 0.5%, 1.0%, 2.5%, 5.0% and 10.0% (w/w) and 0.25-2 mm mature wheat residue at 0% and 2% (w/w) were then added. Cumulative CO₂-C emission from the salt amended and unamended soils was not affected by CaCO₃ addition. To investigate the effect of EC on microbial activity, soil respiration was measured after amending a sandy loam (18.8% clay) and a silt loam (22.5% clay) with varying amount of NaCl to obtain an EC₁:₅ of 1.0-8.0 dS m⁻¹ and 2.5 g glucose C kg⁻¹ soil. Soil respiration was reduced by more than 50% at EC₁:₅ ≥ 5.0 dS m⁻¹. In a further experiment, salinity up to an EC₁:₅ of 5.0 dS m⁻¹ was developed in the silt loam with NaCl or CaCl₂. No differences in respiration at a given EC were obtained between the two salts, indicating that Na and Ca did not differ in toxicity to microbial activity. The effect of different addition rates (0.25-2.0%) of mature wheat residue on the response of respiration to salinity was investigated by adding NaCl to the silt loam to obtain an EC₁:₅ of 2.0 and 4.0 dS m⁻¹. The clearest difference between salinity levels was with 2% residue rate. At a given salinity level, the modelled decomposition constant ‘k' increased with increasing residue addition rate up to 1% and then remained constant. Particulate organic carbon left after decomposition from the added wheat residues was negatively correlated with cumulative respiration but positively correlated with EC. Inorganic N (NH ₄ ⁺ -N and NO ₃ ⁻ -N) and resin P significantly decreased with increasing salinity. Resin P was significantly decreased by addition of CaCl₂ and CaCO₃.

• Publisher: Berlin/Heidelberg : Springer-Verlag,Springer-Verlag,Springer Nature B.V
• Subject: Agriculture / ammonium compounds / Arid climates / Biomedical and Life Sciences / calcium / Calcium carbonate / calcium chloride / Carbon dioxide / carbon dioxide production / carbon sinks / Clay / climate / correlation / Crop residues / Decomposition / electrical conductivity / Evolution / Experiments / glucose / Life Sciences / Microbial activity / Microorganisms / nitrates / Nutrient dynamics / Original Paper / osmotic pressure / Particulate organic carbon / Respiration / Saline soils / Salinity / Salt / Salts / sand / Sandy loam / sandy loam soils / silt / Silt loam / sodium / Sodium chloride / soil respiration / Soil Science & Conservation / toxicity / Wheat