Sodic Soil Reclamation Potential of Gypsum and Biochar Additions: Influence on Chemical, Physical, and Biological Parameters.

ABSTRACT

Reclamation of sodic soils is proving increasingly vital as greater land area becomes salt-affected in the northern Great Plains. Flue gas desulfurization gypsum (FGDG) can be an agriculturally important resource for increasing land productivity through the ameliorating of sodic soils. Along with FGDG, organic amendments have also been considered for reclamation purposes. Biochar is an organic amendment formed through thermal decomposition of organic material, and offers another possible resource for reclaiming Na-affected lands. The aim of this study was to determine sodic soil reclamation potential of FGDG and biochar additions. A laboratory incubation experiment was used to assess this potential through observed soil chemical and physical properties and soil respiration changes. Flue gas desulfurization gypsum treatment rates of 33.6 and 67.2 Mg ha^-1 and biochar treatment rates 16.8 and 33.6 Mg ha^-1 were assessed.  Among chemical analyses, increased electrical conductivity (EC) and decreased sodium adsorption ratio (SAR) were seen with FGDG-treated sodic soil. Biochar-treated sodic soil EC and SAR values remained relatively unchanged in retrospect to untreated sodic soil. Physical properties of water retention and bulk density were positively influenced by the biochar treatments, while FGDG proved to be unfavorable to each of these components. In terms of soil respiration, FGDG-treated sodic soil remained very similar to respiration rate and cumulative respiration of untreated sodic soil over the 52 day incubation period. Additions of biochar to sodic soil significantly increased C mineralization with greater respiration rates and cumulative respiration over the incubation period. An integrated treatment of FGDG and biochar was also investigated, and, incorporating an organic material and high Ca material, may represent a viable option to improving the productivity of sodic soils.

Keywords: sodic soil; land reclamation; gypsum; biochar; soil respiration