By Britt Fossum, PhD Student
The Critical Zone Research (CZR) Group, organized under Principal Investigator Dr. Arindam Malakar (Nebraska Water Center and School of Natural Resources (SNR)), investigates hydrogeochemical dynamics that impact processes within the critical zone (which covers Earth’s land surface extending from the top of the vegetation canopy through the soil to subsurface depths at which fresh groundwater freely circulates) that may ultimately impact transport of contaminants like nitrate into groundwater. The critical zone emerges as a focal point for understanding the delicate balance of carbon and nitrogen cycles.
Research in the CZR group includes laboratory-scale column experiments and field-scale experiments, with work from graduate students within SNR and students co-advised in the department of Agronomy and Horticulture.
PhD student Chandan Kumar has been utilizing column experiments studying reactive nitrogen, specifically nitrate transport and biogeochemical transformation in the vadose zone and its subsequent impact on groundwater pollution, particularly in regions where agricultural practices rely heavily on irrigation. This work involves studying how different irrigation methods such as rain fed, pivot, and gravity irrigation influence nitrogen dynamics that could prevent mobility into groundwater and uses a unique design that simulates a soil and groundwater system to monitor impacts of irrigation and fertilizer at various depths in the vadose zone.
MS student Japhet Dushimeyesu performs research focused on other aspects of agroecological systems including sampling of greenhouse gases and has recently completed a three-year crop sampling event at a research site in Sutherland, NE, where the team collaborates with a local farmer. The crop production data will be used to ground next generation process-based crop simulation models developed by USDAARS Advanced Cropping System Laboratory at Beltsville, Maryland.
PhD student Britt Fossum, co-advised by Dr. Michael Kaiser (Agronomy and Horticulture), primarily focuses on soil amendments and how they impact nitrogen and carbon dynamics in agricultural soils. One project established at UNL research farms (ENREEC and SCAL facilities in Mead, NE and Clay Center, NE) has been ongoing since April 2022. It focuses on biochar field aging and impacts on nitrate retention. A second field experiment established at farmland owned by the City of Lincoln aims to clarify how biochar impacts soil properties when applied at 1-acre scales and how combining biochar with biosolid fertilizer may impact nutrient retention and carbon storage. This field experiment has also enabled study of arsenic mobility in soils following biosolid and biochar application through USGS 104b support.
Research under development in this group, involving PhD student Saurabh Sharma and MS student Kaitlyn Richards, focuses on complete nitrogen budgeting in the vadose zone by using samples from agriculturally intensive sites in various natural resources districts (NRDs) in Nebraska that will be used to compare how water management impacts nitrate reactivity under natural environmental conditions. MS student Kalley Collins, co-advised by Dr. Trenton Franz, is studying enhanced rock weathering of olivine to lock carbon dioxide in cropland. She is leading field experiments in Mead, NE.
