Zahangir Kabir1, Cynthia Kallenbach1, William Horwath1, Dennis Rolston2, and Jefferey Mitchell1. (1) Univ of California at Davis, Dept of Land, Air and Water Resources, One Shields Ave, Davis, CA 95616, (2) Univ of California at Davis, Dept of Land, Air and Water Resources, One Shields Ave, Davis, CA 95616
Carbon dioxide (CO2) and Nitrous oxide (N2O)
emissions from agricultural soils are a significant contribution to global
greenhouse gases. Alternative
agriculture management strategies, such as subsurface drip irrigation, reduced tillage
and winter cover cropping have the potential to reduce both soil CO2
and N2O emissions. A field
trial in California,
planted in processing tomatoes, was used to compare combinations of subsurface
drip irrigation (SDI), strip tillage (ST), and winter cover crop (CC) to furrow
irrigation (FI), conventional tillage (CT) and no cover crop (NCC) to evaluate
system differences in CO2 and N2O emissions. CO2 and N2O fluxes were
measured throughout the growing season every 14 days and during the off-season
every three weeks. Overall, total seasonal CO2 flux was lower in the
SDI treatments than in the FI treatments in the growing season. During
the winter season (October, 2005 to January 2006) no significant difference in total CO2 flux
was found between irrigation treatments.
Annually, the SDI treatments had an emission rate 4% lower than that of
FI treatments. CO2 flux in both SDI and FI increased following
an irrigation event, as did soil moisture. Preliminary N2O
results show that SDI had lower total N2O emissions compared to FI
during the growing season. The N2O flux in the FI treatments was
highest (813.60 ųg m-2 h-1)
in the furrow and remained high at the edge of the bed but was drastically
reduced in the plant line (65.13 ųg m-2 h-1). In contrast, the SDI generally had higher N2O
emissions in the plant line (24.26 ųg m-2 h-1)
than in the edge of the bed and in the furrow (4.87 ųg
m-2 h-1). There was no significant treatment effect on N2O
during the winter season.