Date Available


Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis


Agriculture, Food and Environment


Soil Science

First Advisor

Dr. Chris Matocha


Nitrogen (N) is a crucial element, often limiting productivity in ecosystems. This limitation is relieved N fertilizer additions. No-tillage (NT) agroecosystems are prone to lower N availability translating to lower crop yields. The default explanation for lower N availability in NT is microbial immobilization of added N fertilizer. Historically, N availability is often assessed using chemical extractions such as KCl to evaluate levels of inorganic N in the soil. The possibility of this abiotic clay mineral fixation as mechanism in well-drained NT soils has been overlooked. The objectives of this study are to quantify N availability using KCl, NaCl, and water extractions. To tease out the contributions of biotic pathways from abiotic immobilization, the selective inhibitor methionine sulfoximine (MSX) was employed to inhibit glutamine synthetase. Extractable ammonium decreased suggesting that the KCl might be trapping native ammonium. Ammonium removal from solution was rapid under all conditions. In all treatments, ammonium removal was greater in the presence of MSX when compared with control samples. X-ray diffraction analysis of the clay fraction revealed layers of chlorite, vermiculite, mixed-layer vermiculite-illite, illite, kaolinite, and quartz in the 0 kg N/ha treatment. The implications of these results for NT systems will be discussed.

Digital Object Identifier (DOI)

Funding Information

USDA-NIFA grant (2020-67019-31172)

Available for download on Thursday, December 12, 2024

Included in

Soil Science Commons