Location: Soil Management ResearchTitle: Naturally occurring soil salinity does not reduce N-transforming enzymes or organisms
|DESUTTER, THOMAS - North Dakota State University|
|CASEY, FRANCIS - North Dakota State University|
|BRUGGEMAN, ROBERT - North Dakota State University|
|CLAY, DAVID - South Dakota State University|
Submitted to: Canadian Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2017
Publication Date: N/A
Interpretive Summary: Soil salinity and excess salts cause yield reductions and can limit soil microbial activity. This study was conducted to determine whether reducing soil salinity would improve soil microbial quantities. Over three years, soil salinity was reduced by maintaining residue cover, but, microbial quantity did not increase. Growing 3 different cover crop mixes caused some microbial species to increase, but other species decreased. Overall, the microorganisms found in soil can tolerate a wide range of salts. The ability of the organisms in the soil to tolerate saline conditions is a benefit to producers because producers do not need to worry about restoring the beneficial soil microbial community when reducing soil salinity.
Technical Abstract: Soil salinity can negatively affect plant production and important biogeochemical cycles which are mainly carried out by soil microbes. The objective of this study was to contribute new information on soil biological N transformations by examining the impact primary salinity reduction has on a) the quantity of N-transforming organisms and b) the biological community structure of N-transforming organisms. Alternative management treatments including subsurface tile drainage, gypsum application, and 3 cover crop mixes were tested to reduce salt deposition in the rooting zone. N-transforming organisms were analyzed with qPCR using bacterial/archaeal amoA and nosZ and sequencing by synthesis in conjunction with soil environmental conditions (pH, electrical conductivity (EC) and sodium adsorption ratio, total organic C and inorganic N) over three years. Soil EC was reduced from an average of 7.0 to 4.5 dS m-1 over three years, but the quantity of bacterial/archaeal amoA and nosZ genes did not respond to the reduction in salinity or treatments. However, the community structure and diversity of N-transforming organisms was a function of sampling time and treatment. Abundance of ammonia-oxidizing organisms was lower than typically found in agricultural soils and the quantity and several community members more closely resembled marine and estuary sediments. The diversity of organisms with nosZ genes was relatively constant as this gene are found in phylogenetically diverse organisms. These results suggest N-transforming organisms can tolerate a wide variety of environmental conditions including soil salinity. Therefore, reducing the EC of naturally-induced soil salinity can proceed without special focus on restoring N-transforming organisms.