The Role of the Mineralosphere in Dictating the Fate of Ammonium in Soils

Grants and Contracts Details

Description

Nitrogen (N) is an essential element, often limiting plant productivity in many ecosystems. As a result, N fertilizers are added to enhance crop yields which has also introduced reactive N into the environment. Despite recognition of the importance of N as a nutrient and potential contaminant, uncertainty remains regarding the fate of added ammonium inputs to soil. One possible abiotic immobilization pathway of fertilizer ammonium is clay mineral fixation yet the mechanism of this process, how it competes with biological assimilation, and the reactivity of the bound ammonium are poorly understood. Accordingly, the overall goal of this proposed project is to investigate the contribution of abiotic and biological immobilization processes and nitrification processes in natural clay mineral assemblages and bulk soils from undisturbed sod and long term no-tillage soil samples from four locations spanning a climate gradient (MAP 400-1300 mm). This goal will be achieved through two specific objectives: 1) Perform reactivity (kinetic) studies of 15,14 NH 4 + removal with bulk soil and clay fractions from these sites using wet chemical and cutting-edge spectroscopic techniques (NanoSIMS, ATR-FTIR, XRD, and SEM-EDS); 2) Investigate the transformations of bound (clay mineral- and microbial-bound NH 4 + ) from the four sites to nitrify to NO 2 - and NO 3 - in soil using wet chemical and in situ spectroscopic techniques (ATR-FTIR). Historically, following the clay mineral fixation of added fertilizer ammonium relied heavily on wet chemical extractions using mineral acids to dissolve the silicate structure. This proposed work is both creative and original because it combines spectroscopic tools (NanoSIMS and ATR-FTIR) for following reactivity of ammonium with clay minerals with stable isotope measurements and wet chemical experiments to unravel the complexities of N transformations in undisturbed grassland and no-tillage agroecosystems. A n expected outcome is fundamental rate data of abiotic versus biological immobilization processes and how this is related to closely linked nitrification pathways, information that can be incorporated in transport models. This proposed study corresponds to USDA-AFRI’s program area priority to study nutrient cycles and management, including interrelationships between soil chemical, biological, and physical characteristics and processes controlling nutrient fate in soils. This research is a timely pursuit given the desire to minimize adverse environmental consequences of reactive N additions into ecosystems.
StatusActive
Effective start/end date6/1/205/31/24

Funding

  • National Institute of Food and Agriculture: $439,757.00

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