Nutrient Management Research Database

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.

• 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.

• 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%.