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There is a strong need to identify agricultural management practices that maintain agronomic productivity while diminishing soil N2O emissions. The yield-scaled N2O emissions (YSNE) indicator can help to evaluate the adequacy of a given agricultural practice under both aspects. Long-term (18-yr) soil water and mineral N dynamics, crop biomass and yields, and 2011–2012 soil N2O emissions and ancillary variables were measured on barley (Hordeum vulgare L.) production in a tillage (conventional tillage, CT; no-tillage, NT) and N rate (0, 60 and 120 kg N ha−1) combination under rainfed Mediterranean conditions (NE Spain). Once evaluated, the STICS soil-crop model was used to simulate the 18-yr soil N2O emissions of each tillage system under increasing N rates (0, 30, 60, 90 and 120 kg N ha−1) in order to identify optimum management to reduce YSNE, being initialized with observed data. Cropping season precipitation was highly variable during the experiment, being a key regulating mechanism for crop yields and simulated soil N2O emissions. Crop yield under NT with N outperformed CT in 11 years. STICS performed reasonably well when simulating cumulative N2O emissions and ancillary variables with model efficiencies greater than 0.5. The 18-yr average simulated cumulative N2O emissions were 0.50, 0.82 and 1.09 kg N2O-N ha−1 yr−1 for CT-0, CT-60 and CT-120, respectively, and they were 0.53, 0.92 and 1.19 kg N2O-N ha−1 yr−1 for their counterparts under NT. These averages mask a large variability between years, according to precipitation. The 18-yr mean yield-scaled N2O emissions were 2.8–3.3 times lower under NT, compared to the corresponding CT treatments. Under CT, N application would increase YSNE in most years while YSNE would be more resilient to the application of increasing N rates under NT. Our work demonstrates that in rainfed Mediterranean systems NT is a win-win strategy for the equilibrium between agricultural productivity and low soil N2O emissions.

Los resultados que se presentan en este documento corresponden a los 4 primeros años de experimento (campañas 2010-2011, 2011-2012, 2012-2013 y 2013-2014) en los que el sistema de cultivo fue un monocultivo de cebada. El tratamiento LC consistió en el manejo tradicional de la zona con un pase de grada de discos seguido de uno de cultivador antes de la siembra. En el caso de la SD no se realizó ninguna labor de preparación del suelo, aplicándose glifosato a una dosis de 1,5 L ha-1, antes de la siembra.

The effect of delaying sowing date and maturity class on no-till (NT) winter cereal performance was studied over two periods of 3 yr each. A 3 (sowing date) × 2 (maturity class) randomized complete block design was run for 3 yr with barley (Hordeum vulgare L.) (B-) (2006–2007 to 2008–2009) and soft wheat (Triticum sp.) (W-) (2009–2010 to 2011–2012) in northeastern Spain. Sowing dates corresponded to October (D1- the standard farming practice), November (D2), and December (D3). Maturity classes corresponded to early (-EC) and medium (-MC). Crop aboveground biomass, grain yield, and yield components were analyzed. The water use efficiency of aboveground biomass (WUEb) and grain yield (WUEy), and nitrogen use efficiency (NUE), were calculated. Averaging barley maturity classes and cropping seasons, D2 and D3 increased their grain yields 59 and 46%, respectively, when compared to D1. A greater number of grains per spike, as well as higher WUEb and NUE were observed in D2 and D3 compared to D1 in two of the three barley seasons. A greater thousand kernel weight (TKW) and higher WUEy were observed when sowing was delayed. Averaged across years, WEC presented a greater yield and aboveground biomass for D2 and D3 compared to D1, while for WMC there were no grain yield differences seen between the sowing dates, aboveground biomass or yield components. Our results demonstrate that, in western Mediterranean areas, sowing delay under NT can increase grain yield, WUE and NUE of winter barley, and also of wheat but only during wet years.

Tillage and N fertilization strategies including mineral and organic sources need to be studied in combination given their importance on the production cost that farmers face and their potential interaction on crop performance. A four-year (2010–2014) experiment based on barley monocropping was carried out in NE Spain in a typical rainfed Mediterranean area. Two tillage treatments (CT, conventional tillage; NT, no-tillage) and three rates of N fertilization (0; 75 kg N ha−1, applied at top-dressing; 150 kg N ha−1, applied at pre-sowing and at top-dressing at equal rate), with two types of fertilizers (ammonium-based mineral fertilizer and organic fertilizer with pig slurry), were compared in a randomized block design with three replications. Different soil (water and nitrate contents) and crop (above-ground biomass, grain yield, yield components and N concentration in biomass and grain) measurements were performed. Water- and nitrogen use efficiencies (WUE and NUE) as well as other N-related indexes (grain and above-ground biomass N uptake; NHI, nitrogen harvest index; NAR, apparent nitrogen recovery efficiency) were calculated. Barley above-ground biomass and grain yield were highly variable and depended on the rainfall received on each cropping season (ranging between 280 mm and 537 mm). Tillage and N fertilization treatments affected barley grain yields. No-tillage showed 1.0, 1.7 and 6.3 times greater grain yield than CT in three of the four cropping seasons as a result of the greater soil water storage until tillering. Water scarcity during the definition of the number of spikes per m2 under CT would have compromised the compensation mechanism of the other two yield components. Pig slurry application led to the same (3 of 4 years) or higher (1 of 4 years) grain yield than an equivalent rate of mineral N fertilizer. Regardless the N origin, barley yield did not respond to the application of 150 kg N ha−1 split between pre-sowing and top-dressing compared to the