Methane Emissions and Ammonia Volatilization from Drill-Seeded, Delayed-Flood Rice on a Silt-Loam Soil in Arkansas

<p>The Environmental Protection Agency (EPA) currently uses a single methane (CH4) emissions factor of 160 kg CH4-C ha-1 for a primary rice (Oryza sativa L.) crop. The emissions factor is based on studies that do not adequately represent current management practices in Arkansas. Another concern is pre-flood fertilizer nitrogen (N) management, as the common N source, urea, is prone to loss via ammonia (NH3) volatilization. Thus, the objective of this research was to investigate trace gas emissions from rice on a silt-loam soil, including CH4 emissions as influenced by nitrogen (N) fertilization (i.e., optimal N and no N) in 2011, and previous crop [i.e., soybean (Glycine max L.) or rice] and cultivar (i.e., semi-dwarf, standard-stature, and hybrid) in 2012, and to assess the impact on grain yield of ammonia (NH3) volatilization from preflood urea application with and without the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT). A chamber-based method was used to measure methane fluxes and linear interpolation and numerical integration between individual sample dates was performed to determine seasonal emissions. Ammonia volatilization was measured using semi-open static chambers. In 2011, no differences (P > 0.05) were measured in CH4 emissions due to N fertilization where mean annual emissions were 195 kg CH4-C ha-1. Methane emissions in 2012 were greater (P < 0.05) when rice was the previous crop (184 kg CH4-C ha-1) compared to when soybean was the previous crop (127 kg CH4-C ha-1), and emissions were greater from the semi-dwarf pure-line cultivar (169 kg CH4-C ha-1) and standard-stature pure-line cultivars (186 kg CH4-C ha-1), which did not differ, compared to the hybrid cultivar (111 kg CH4-C ha-1). Ammonia volatilization was reduced (P < 0.05) and grain yield increased when using NBPT compared to untreated urea. Methane results suggest the EPA's emissions factor potentially overestimates CH4 emissions in Arkansas, as 70% of rice production follows soybean and 50% </p> <p>of production is from hybrid rice. Results also indicate NH3 volatilization can be reduced by the usage of NBPT. Thus, trace gas emissions measurements from rice will improve long-term sustainability assessments of rice. </p>

Name thesis:degree_name

Doctor of Philosophy in Crop, Soil & Environmental Sciences (PhD)

Level thesis:degree_level

Dissertation

Year dc:date.available

2014

Author dc:creator

• Rogers, Christopher Wade

Advisor dc:contributor.advisor

• Norman, Richard J.

Contributors dc:contributor

• Brye, Kristofor R.
• Evans-White, Michelle A.

• Ammonia Volatilization
• Methane
• Rice
• Trace Gases
• Agronomy and Crop Sciences
• Biogeochemistry

Repository record dc:identifier

https://scholarworks.uark.edu/etd/2355

OAI identifier oai:identifier

oai:scholarworks.uark.edu:etd-3894