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Nutrient Management Research Database
General Information
Research Title
Research Specifications
Authors
Summary/Abstract from Original Source
Agricultural management practices such as subsurface drip irrigation (SDI) and winter legume cover cropping (WLCC) influence soil water dynamics as well as carbon and nitrogen cycling, potentially changing emission rates of soil CO2 and N2O, principal greenhouse gases. A split plot tomato field trial in California’s Central Valley was used to evaluate the use of SDI and WLCC on event-based CO2 and N2O emissions. SDI and WLCC were compared to the region’s more conventional practices: furrow irrigation (FI) and no cover crop (NCC). Our results indicate that SDI offers the potential to manage cover crops without the significant increases in greenhouse gas production during the growing season as seen under FI cover-cropped systems. The highest N2O emissions occurred during the beginning of the rainy season in November in the FI–WLCC treatment (5mgm-2 h-1) and the lowest in August in the SDI–NCC treatments (4.87 gm-2 h-1). CO2 emissions ranged from 200mgm-2 h-1 during the rainy season (winter) and >500m-2 h-1 during the growing season. Though no differences were detected in CO2 emissions between irrigation practices, mean CO2 emissions under WLCC were 40% and 15% greater compared to NCC under FI and SDI, respectively. The treatment with the greatest effect on CO2 and N2O emissions was WLCC, which increased average growing season N2O and CO2 emissions under FI by 60 gN2Om-2 h-1 and 425mgCO2m-2 h-1 compared to NCC. In SDI there was no effect of a cover crop on growing season CO2 and N2O emissions. In the rainy season, however, SDI N2O and CO2 emissions were not different from FI. In the rainy season, the cover crop increased N2O emissions in SDI only and increased CO2 emissions only under FI. Subsurface drip shows promise in reducing overall N2O emissions in crop rotations with legume cover crops.
Research Highlights
Design and Methods
- The study plots were initiated in 2003 at the Russell Ranch Sustainable Agricultural Research Facility on the University of California, Davis campus.
- Field data collection began in spring 2006.
- Treatments were set up as a randomized split plot design with subsurface drip irrigation (SDI) and furrow (FI) irrigation as the main plot treatments.
- Subplot treatments were winter legume cover crop (WLCC) and no winter legume cover crop (FI).
- The WLCC treatments were seeded with a 1:3 mass ratio of hairy vetch and Australian winter pea.
- The cover crop was mowed, mulched and incorporated in spring 2006.
- Beds were on 1.52 meter spacing. Drip tape for SDI plots was installed at a depth of 25.4cm in 2003.
- Irrigation events were usually every 6-10 days for FI and every 2-4 days for SDI.
- Plots were fertilized with the same total N input according to typical grower practices.
- Soil samples were taken for total C, N and inorganic N throughout the experiment, focusing on times of cover crop biomass increases and following cover crop incorporation.
- Soil C02 and N20 sampling measurements were taken from the plant line, shoulder of the bed, and furrow for all treatments and a weighted average of the 3 zones was used to estimate total crop-bed emissions for each sampling.
- N20 and CO2 sampling were carried out on the same day.
- Emissions for both gases were measured every 10 days throughout the growing seasons with greater frequency around fertilization and tillage events.
- During the rainy season, gas measurements were taken every 2-3 weeks.
- At the time of each gas sampling, soil temperature and soil moisture were measured at 6 and 12-cm depths.
Results
- Total soil C and N did not change significantly under irrigation treatments.
- WLCC had a significant positive effect on the average soil C content.
- Total soil N was not affected by the cover crop.
- The cover crop mix added a mean 107 kg biomass N/ha and 1.5 t biomass C/ha to the WLCC treatments annually.
- Average tomato crop yields were 79t/ha and did not vary between treatments.
- SDI was estimated to have over 100% higher water use efficiency compared to that of FI.
- Soil temperature, irrigation events and WLCC had the largest influence on N20 emissions and soil moisture was also positively correlated to N20.
Additional Information
Tags (links to other subject matter in database)
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