Theses and Dissertations

Date of Award


Document Type


Degree Name

Master of Science (MS)


Agricultural, Environmental, and Sustainability Sciences

First Advisor

Dr. Alexis Racelis

Second Advisor

Dr. Bradley Christoffersen

Third Advisor

Dr. Pushpa Soti


Many farms use leguminous cover crops as a nutrient management strategy to reduce their need for nitrogen fertilizer. Biological nitrogen fixation (BNF) depends on a symbiotic relationship between legumes and nitrogen-fixing rhizobia. Under certain conditions despite inoculation with appropriate rhizobial strains, this symbiosis fails to form. Such failure was observed in a 14-acre winter cover crop trial in the Rio Grande Valley of Texas when three legume species (forage pea, crimson clover, and hairy vetch) produced no signs of nodulation and nitrogen fixation. This study examined nitrogen, phosphorus, moisture, micronutrients and biotic interference as potential causes for the failure and assessed arbuscular mycorrhizal fungi as a potential intervention to improve nodulation outcomes. Results from a controlled greenhouse study confirm moisture and micronutrient deficiencies as major suspects in the nodulation failure. Nitrogen and phosphorus deficiencies however were not likely causes, nor was mycorrhizal inoculation an effective intervention to improve nodulation results.


Copyright 2019 Stephanie L. Kasper. All Rights Reserved.

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