369-4

See more from this Division: SSSA Division: Soils & Environmental Quality
See more from this Session: Nitrogen Fertilizer: Practices for Minimizing Environmental Impacts

Wednesday, November 18, 2015: 11:50 AM
Minneapolis Convention Center, M101 C

ABSTRACT WITHDRAWN

Abstract:

Improved N fertilizer management practices can increase rice yields and mitigate global warming potentials (GWP). Three field experiments were conducted to quantify the effect of fertilizer N and placement on emissions of CH4 and N2O from flooded rice systems. We hypothesized that in continuously flooded rice systems in which GWP is dominated by CH4 emissions, deep placement of urea in bands would reduce CH4 emissions with minimal effect on N2O emissions. Rice yields and greenhouse gas (GHG) emissions were measured from field experiments which had three treatments: (1) no N (N0), (2) urea broadcast (U-BR) on soil surface and (3) urea banded at 7.5 cm soil depth (U-BA). All urea was applied in a single application before flooding in preparation for planting at N rates of 143-150 kg N ha-1. Emissions of CH4 and N2O were measured throughout the rice growing season using a vented flux chamber and gas chromatograph. Across all fields, N fertilizer application increased yield by about 121% and average N use efficiency (NUE) was 37 kg grain kg-1 N urea with no yield differences in N fertilized treatments. Daily N2O emissions were low to negative while daily CH4 emissions varied during the vegetative period. Total seasonal CH4 emissions ranged from 6.3 to 297 kg CH4-C ha-1 season-1 setting CH4 emission as the major source of GWP emissions during the growing season. Addition of urea-N increased GWP (by increasing CH4 emissions) by 32% on average; but there was no effect of urea-N placement on either CH4 or N2O emissions.

See more from this Division: SSSA Division: Soils & Environmental Quality
See more from this Session: Nitrogen Fertilizer: Practices for Minimizing Environmental Impacts