Effects of Saline Soil Amelioration on Soil Nitrification.

Soil salinity negatively impacts plant and microbial growth by affecting osmotic balances and specific ion toxicities which reduces nitrogen mineralization, ammonification, fixation, and nitrification. Due to the negative effects of salinity on nitrogen transformations and crop yields, remediation strategies to reduce the impacts of salinity are employed.  In the northern Great Plains where primary salinity is a result of parent materials and a high water table, amelioration may include reducing surface evaporation, reducing capillary rise of salt-affected groundwater, tile drainage installation, or additions of organic materials. A randomized complete block design experiment with split plot arrangement was established on a Bearden silty clay loam, saline phase (fine-silty, mixed, superactive, frigid Aeric Calciaquolls) soil.  Whole plots consist of drainage treatments (tile drained and non-tile drained) with the split plots consisting of a control and three cover crop treatments.  An additional 4.48 Mg gypsum ha^-1 treatment was included in the study to reduce the risk of sodification during salt removal.  The objectives of this study are to: 1) determine the effect of salinity management strategies on soil enzyme activities which are crucial to nitrogen transformations and 2) identify changes in functional gene copy numbers of ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB). Changes in soil nitrification as a result of management strategies can give a short-term indication of remediation success.