Nutrient Management Research Database

Knowing underlying practices for current greenhouse gas (GHG) emissions is a necessary precursor for developing best management practices aimed at reducing N2O emissions. The effect of no-till management on nitrous oxide (N2O), a potent greenhouse gas, remains largely unclear, especially in perennial agroecosystems. The objective of this study was to compare direct N2O emissions associated with management events in a cover-cropped Mediterranean vineyard under conventional tillage (CT) versus no-till (NT) practices. This study took place in a wine grape vineyard over one full growing season, with a focus on the seven to ten days following vineyard floor management and precipitation events. Cumulative N2O emissions in the NT system were greater under both the vine and the tractor row compared to CT, with 0.15±0.026 kg N2O–Nha-1 growing season-1 emitted from the CT vine compared to 0.22±0.032 kg N2O–Nha-1 growing season-1 emitted from the NT vine and 0.13±0.048 kg N2O–Nha-1growing season-1 emitted from the CT row compared to 0.19±0.019 kg N2O–Nha-1 growing season-1 from the NT row. Yet these variations were not significant, indicating no differences in seasonal N2O emissions following conversion from CT to NT compared to long-term CT management. Individual management events such as fertilization and cover cropping, however, had a major impact on seasonal emissions, indicating that management events play a critical role in N2O emission patterns.

• The study was conducted in a wine grape vineyard (Vitis vinifera, var. Zinfandel) in Arbuckle, CA for one full growing season.
• The vineyard was established in 1989 and a leguminous cover crop mix was planted in tractor rows starting in 1991, which was then incorporated into the soil each spring.
• The entire vineyard was fertilized once at a rate of 5kg N/ha through the irrigation system in late August.
• The vineyard was divided into 2 rows each of no-tillage (NT) and conventional tillage (CT), with measurement locations selected in under the vines and in tractor rows.
• For the CT treatment, tillage occurred 3 times with discing to a depth of 15cm.
• The NT treatments were not tilled after 2008, but the cover crop was mowed twice throughout the study period, resulting in 47kg organic N/ha in the tractor rows.
• N20 fluxes were measured using a vented closed-flux chamber and analyzed using electron capture gas chromatography.
• Three replicate soil samples to 15cm depth were taken within 30cm of the N20 sampling chamber during each sampling chamber to assess soil moisture content, ammonium and nitrate concentrations, pH, Total C and N content.

• There were no significant differences in cumulative N20 emissions between the NT and CT systems.
• For both treatments, the largest fluxes were found following a fertilization event under the vines and after cover crop management and precipitation events in the tractor rows.
• The fluxes for all management events were short-lived, returning to background N20 levels within a week after peak emissions.
• Both tillage practices showed similar trends in soil moisture.