Soil N2O emissions in Mediterranean arable crops as affected by reduced tillage and N rate

Nitrous oxide (N 2 O) is emitted from agricultural soils as a product of biotic pathways of the nitrogen (N) cycle. Agricultural practices may affect soil water content, temperature and N availability, and consequently N 2 O emissions. Thus, it is necessary to identify strategies to mitigate N 2 O emissions while maintaining crop yields. This two-year study on durum wheat and sunflower in a Mediterranean environment evaluated the influence of tillage intensity (plowing vs. minimum tillage) and N fertilizer rate (N0, N1 and N2: 0, 110 and 170 kg N ha −1 , respectively, for wheat, and 0, 80 and 140 kg N ha −1 , respectively, for sunflower) on crop yields and N 2 O emissions. Reducing the N fertilizer rate by ca. 40% resulted in an average mitigation of ca. 35% of cumulative N 2 O emissions during the growing season of both crops. From N1 to N2, the grain yield of sunflower did not increase, but that of wheat did so by ca. 25%. Indeed, yield-scaled N 2 O emissions of N0, were the highest in wheat (259 ± 45 g N 2 O–N Mg −1 dry grain, 12.2 ± 2.0 g N 2 O–N kg −1 N uptake) and the lowest in sunflower (62 ± 7 g N 2 O–N Mg −1 dry grain, 2.0 ± 0.2 g N 2 O–N kg −1 N uptake). Reducing tillage intensity decreased cumulative N 2 O emissions significantly only for sunflower during the second year (by 35%), but not for any other treatment. The effect of the reduced tillage depth on grain yield varied between the 2 years, being negative only under wetter growing seasons (− 12% in wheat and − 9% in sunflower).