Nutrient Management Research Database
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Summary/Abstract from Original Source
There is a strong need to identify the combination of tillage and N fertilization practices that reduce the amount of nitrous oxide (N2O) emissions while maintaining crop productivity in dryland Mediterranean areas. We measured the fluxes of N2O in two field experiments with 3 and 15 years since their establishment. In the long-term experiment, two types of tillage (NT, no-tillage, and CT, conventional intensive tillage) and three mineral N fertilization rates (0, 60 and 120 kg N ha−1) were compared. In the short-term experiment, the same tillage systems (CT and NT) and three N fertilization doses (0, 75 and 150 kg N ha−1) and two types of fertilizers (mineral N and organic N with pig slurry) were compared. N2O emissions, water-filled pore space, soil mineral N content, grain yields, N-biomass inputs and soil total nitrogen (STN) stocks were quantified and the N2O yield-scaled ratio as kg of CO2 equivalents per kg of grain produced was calculated. In both experiments tillage treatments significantly affected the dynamics of N2O fluxes. Cumulative losses of N as N2O were similar between tillage treatments in the long-term field experiment. Contrarily, although not significant, cumulative N losses were about 35% greater under NT than CT in the short-term experiment. NT significantly increased the production of grain and the inputs of N to the soil as above-ground biomass in both experiments. Averaged across fertilizer treatments, CT emitted 0.362 and 0.104 kg CO2equiv. kg grain−1 in the long-term and the short-term experiment, respectively, significantly more than NT that emitted 0.033 and 0.056 kg CO2 equiv. kg grain−1, respectively. Nitrogen fertilization rates did not affect the average N2O fluxes or the total N losses during the period of gas measurement in the long-term experiment. Contrarily, in the short-term experiment, N2O emissions increased with application rate for both mineral and organic fertilizers. The use of pig slurry increased grain production when compared with the mineral N treatment, thus reducing the yield-scaled emissions of N2O by 44%. Our results showed that in rainfed Mediterranean agroecosystems, the use of NT and pig slurry are effective means of yield-scaled N2O emissions reduction.
Research Highlights
Design and Methods
- The effects of conventional tillage and no-till on nitrous oxide emissions and yield were compared at three levels of N fertilization at two locations, a long term (15 year) and short term (3 year) experimental site.
- This experiment was carried out in a barley cropping system.
- Mineral fertilizer was applied at a rate of 0, 54, and 108 lbs N/ac at the long term experimental site. At the short term site, both mineral fertilizer and pig slurry were applied at the rate of 0, 67, and 134 lbs N/ac.
- Two different sources of N fertilizer, mineral or pig slurry, were compared. For the mineral fertilizer, one third of this N was applied as ammonium sulfate prior to seeding, while the rest was applied as ammonium nitrate at tillering.
- Nitrous oxide emissions along with soil nitrogen and moisture levels were monitored for the duration of the experiment.
Results
- N2O emissions did not differ between tillage systems at the long term site, while N2O losses were 35% higher under conventional tillage at the short term site.
- No till increased grain yield at both experimental sites.
- Yield scaled emissions, the total amount of N2O emitted per unit of grain produced, were significantly lower under no till due to the increased yields.
- N2O emissions were not affected by N fertilization rate at the long term site, while increased N rates did increase emissions at the short term site.
- Pig slurry increased grain yields as compared to the mineral fertilizer, and therefore reduced yield-scaled N2O emissions by 44%.