Document Type

Thesis - Open Access

Award Date

2018

Degree Name

Master of Science (MS)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

David E. Clay

Abstract

Greenhouse gases (GHG) absorb and emit radiant energy in the thermal range. Their concentrations in the atmosphere are increasing and becoming an ever increasing issue as the Earth’s average temperature continues to rise. Agricultural practices, such as applying nitrogen fertilizer to increase crop yield can be a major source of GHG emissions and methods are needed to decrease these emissions. The measurements of GHG emissions have been difficult, expensive, and erratic. However, advancing technologies have increased the accuracy and confidence in measuring GHG emissions. The objectives of this study were to determine the 1) effects of different nitrogen fertilizer sources, 2) application dates on greenhouse gas (nitrous oxide and carbon dioxide) and ammonia emissions and 3) sampling requirements and associated errors. Gas samples were collected and measured for 21 days following nitrogen fertilizer application every four hours. A polymer coated urea (Environmentally Smart Nitrogen, ESN), urease inhibitor (NBPT) coated urea, and urea fertilizer were used as the nitrogen fertilizer source and applied at a rate of 224 kg N ha-1. Soil was sampled at the start and completion of each fertilizer application date for ammonium and nitrate concentrations and the microbial community was evaluated using the Phospholipid Fatty Acid (PLFA) technique. The enhanced efficiency nitrogen fertilizers (urease coated urea and polymer coated urea) reduced nitrous oxide emissions but did not influence carbon dioxide or ammonia emissions. Fertilizer application date, fertilizer source, and application season had a large impact on greenhouse gas emissions. Applying urea fertilizer, regardless of season, increased ammonia and nitrous oxide emissions, but did not increase carbon dioxide emissions. In the fall, as soil temperature decreased, nitrous oxide and carbon dioxide emissions decreased; although, ammonia emissions was less influenced by soil temperature. The decrease in carbon dioxide and nitrous oxide emissions were was attributed to decreasing microbial activity and nitrification rates. In the spring, the relationship between temperature and nitrous oxide emissions was less prevalent. Seasonal differences may have resulted from changes in the microbial community structure. Nitrous oxide results followed a similar trend to available nitrate detected in the soil (0 – 60 cm). Sampling for N2O-N at average air temperatures resulted in underestimating emissions and different fertilizer application dates resulted in changes in variance structure. This study showed that GHG emissions could be reduced by applying enhanced efficiency nitrogen fertilizers (urease coated urea and polymer coated urea) and adjusting the fertilizer application date.

Library of Congress Subject Headings

Nitrogen fertilizers -- Environmental aspects.
Greenhouse gases.
Crops and climate.
Climatic changes.
Greenhouse gas mitigation.
Urea as fertilizer.

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

256

Publisher

South Dakota State University

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Rights Statement

In Copyright