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The irrigated cropping systems in South Europe could benefit from soybean [Glycine max(L.) Merr.] introduction in their maize (Zea maysL.)‐based crop rotations. However, sustainable weed management strategies are needed for soybean growers under Mediterranean irrigated conditions. This work aimed to assess the weed control efficacy, and the soybean performance, of alternative management practices for single‐ and double‐cropped soybean. Two field experiments were carried out in northeast Spain in the period 2019–2021. Row width narrowing (75–37.5 cm), herbicide application (yes/no), and roller‐crimped rye [Secale cereal(L.) M.Bieb.] cover crop (yes/no) were assessed in the single cropping system experiment (SCS). In the barley‐soybean double cropping system experiment (DCS), row width narrowing and herbicide application were assessed. In the SCS, the presence of rye cover crop reduced weed biomass up to 92% compared to the controls without herbicide and cover crop in 2020. In 2021, no effect of the cover crop on weed pressure was found due to the low amount of rye biomass accumulated (11.8 and 3.4 ton DM ha−1in 2020 and 2021, respectively). In the DCS, herbicide application attained the expected weed control. Row width narrowing to 37.5 cm did not have an impact on weed pressure nor on soybean yield in either experiment. We concluded that herbicide reduction for single‐cropped soybean under Mediterranean irrigated conditions can be achieved by roller‐crimping a rye cover crop, provided enough rye biomass is accumulated. In the DCS, our results indicated that further research is needed to find alternatives to chemical weed control. Roller‐crimped rye cover crop controlled weeds in soybean when enough biomass was accumulated.Roller‐crimped rye effectively controlled most weed species, especially Datura stramoniumL. and Setaria adhaerens(Forssk) Chiov.Narrowing row width from 75 to 37.5 cm did not improve weed control or soybean yield.

A significant challenge in our time is to produce sufficient agricultural products on limited farmable land to meet the needs for food, feed, fiber, and industrial uses in the face of a changing climate. Conventional cropping systems mostly rely on inputs, such as fertilizers and pesticides, to boost crop yields. However, excessive inputs increase production costs and entail more direct and indirect emissions of greenhouse gases to the atmosphere that negatively impact the environment. Finding sustainable ways to increase crop productivity with little or no impact on the environment is the primary goal of modern agriculture. This review reveals that temporal-spatial diversification of crop rotations is critically needed to advance toward this goal sustainably. We find that (i) intensified crop rotations enhance carbon conversion from atmospheric CO2into plant biomass and thus sequester more carbon into soil; (ii) diversified crop mixtures improve system resilience, i.e., increased resistance to pest/disease incidence and weed infestation, and faster recovery after removal of the abiotic or biotic stress; (iii) diversifying crop rotations increases crop yields at the system level with improved water and fertilizer use efficiencies; (iv) legume-based crop rotations reduce the need for synthetic nitrogen fertilizers thus lowering N2O and CO2emissions to the atmosphere; (v) crop diversity leads to soil microbiome diversity that optimizes soil microenvironment, improving soil health. We believe that developing and adopting of diversified cropping systems are key factors for agricultural policy setting and a top priority for on-farm decision-making to increase crop productivity and enhance soil health, while reducing negative environmental impacts.

The aim of this study was to evaluate the impact of 21 years of tillage and N fertilization and the conversion from a rainfed to an irrigated cropping system on soil organic C (SOC). The study was carried out in northeastern Spain in a long‐term tillage and N rate field experiment established in 1996 under barley rainfed conditions, which in 2015 was converted into irrigation with corn. Three types of tillage (conventional tillage, CT; reduced tillage, RT; no‐tillage, NT) and three mineral N fertilization rates (0, 60, and 120 kg N ha−1under barley, and 0, 200, and 400 kg N ha−1under corn) were compared. Annual C‐inputs as aboveground crop residues and annual SOC sequestration rate (∆SOCrate) (0–40 cm depth) were calculated in three different periods (P1, P2 and P3) under rainfed (‐R) and irrigated (‐I) conditions (P1‐R, from 1996 to 2009; P2‐R, from 2009 to 2015; P3‐I, from 2015 to 2017). At the end of P3‐I, particulate organic C (POC) was measured from the 0–5, 5–10, 10–20, 20–30, and 30–40 cm depths. Averaged over all treatments, ∆SOCratewas 492, 222, and 969 kg C ha−1yr−1for P1‐R, P2‐R, and P3‐I, respectively. In P1‐R and P3‐I, C‐input explained 70% of the variability of ∆SOCrate. In P1‐R, ∆SOCratefollowed the order NT > RT > CT, while for N rate, order was high > medium > 0. In P3‐I at the highest N rate, ∆SOCratefollowed the order NT > RT > CT. In P2‐R, ∆SOCratedid not show differences between tillage and/or N rate treatments. The increase in SOC after conversion from a rainfed to an irrigation system was mainly explained by POC, which was increased by 75% compared to the previous rainfed period. The modification of the cropping system through the introduction of irrigation and adequate crop management practices under no‐tillage and adjusted N fertilizer rates can contribute to the sequestration of large amounts of atmospheric CO2.

Irrigation and soil management can impact soil nitrous oxide (N2O) emissions. Flood and sprinkler irrigation systems together with conventional tillage are the main practices used in the high yielding maize systems in Mediterranean Spain. The objective of this field work was to quantify the effect of the irrigation system (i.e., flood, F; and sprinkler, S) and the soil tillage system (i.e., conventional tillage, CT; no‐tillage maintaining the maize stover, NTr; and no‐tillage removing the maize stover, NT) on the N2O emissions from the soil during 3 yr (2015, 2016, and 2017). S irrigation, with mean values of 1.35 kg N2O‐N ha−1yr−1throughout the 3 yr, obtained 42% lower N2O emissions than F irrigation. On average of the three growing seasons, yield‐scaled N2O emissions by grain yield and by grain N uptake in F irrigation were two‐fold higher than in S irrigation. Moreover, in one out of three growing seasons (2017), no‐tillage systems (i.e., NTr and NT) showed greater yield‐scaled N2O emissions compared with CT. The higher maize grain yield with the S irrigation compared to F irrigation, as well as the lower N2O emissions reported under S irrigation resulted in the reduction of the yield‐scaled N2O emissions. Our findings highlight the role of sprinkler irrigation decreasing N2O emissions in comparison to flood irrigation in Mediterranean agroecosystems.

Sowing delay and cultivar effects on cereal production and water and N use efficiencies were studied.Sowing delay increased grain yield due to greater number of grains per m2.Sowing delay maximized the efficiency in the use of resources. 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 vulgareL.) (B‐) (2006–2007 to 2008–2009) and soft wheat (Triticumsp.) (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 WUEband 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 WUEywere 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.

Core IdeasSoil GHG emissions were quantified in four fertilization scenarios in irrigated corn.Fertilization scenarios had minor effect on CO2and CH4emissions.Soil mineral N level affected N2O emissions and yield‐scaled N2O emissions. Agricultural soils emit greenhouse gases (GHG). Excessive application of N fertilizer may lead to the accumulation of mineral N in the soil, which is susceptible to loss to the environment. The objective of this study was to quantify the effect of two levels of available mineral N before planting (L, low; H, high) and two rates of NH4NO3fertilizer (0 and 300 kg N ha−1) on soil CH4, CO2, and N2O emissions in a sprinkler‐irrigated corn (Zea maysL.) field located in northeastern Spain during two growing seasons (2011 and 2012). For both soil N levels at planting, several sampling dates showed higher N2O emissions in the 300 kg N ha−1treatment than the 0 kg N ha−1treatment. Applications of N fertilizer resulted in a short‐lived increase of N2O emitted. Differences among fertilization treatments were found for soil CO2emissions in 2011 and for soil N2O emissions in 2011 and 2012. No differences were found between treatments for CH4. In the 2012 season, the application of 300 kg N ha−1in the L scenario reduced N2O yield‐scaled emissions (g N2O‐N kg−1aboveground N uptake) by 30% due to a significant increase in corn yield (7.6 Mg grain ha−1) compared with the treatment without N. Conversely, under the H scenario, N application doubled yield‐scaled N2O emissions. Results of this study demonstrate that fertilization strategies need to take into account mineral N levels in the soil before sowing to reduce GHG emissions during the growing season.

Agricultural management practices play an important role in soil organic carbon (SOC) protection within soil aggregates. However, there is a lack of information on the effects of N fertilization on C protection within aggregates under no‐tillage (NT) systems. The effects of organic fertilization (with pig [Sus scrofa] slurry and poultry manure) and mineral N fertilization on soil aggregation and physical C protection dynamics under NT soils were investigated. Two experiments were established in a semiarid area of northeastern Spain. In the organic fertilization experiment, treatment with pig slurry at two N rates (100 and 200 kg N ha−1), poultry manure (100 kg N ha−1), and a control (0 kg N ha−1) treatment were compared. In the mineral fertilization experiment, increasing rates of N fertilizer (0, 40, 80, 120, and 160 kg N ha−1) were compared. Water‐stable macroaggregates (>0.250 mm) and their C concentration, the distribution of dry‐sieved aggregates, total SOC and microbial biomass carbon (MBC) were quantified in the soil surface in two cropping seasons. Organic fertilizers slightly increased the proportion of water‐stable macroaggregates but caused no differences in MBC, SOC, or water‐stable macroaggregate C concentration. In the mineral N fertilization experiment, similar water‐stable macroaggregate, water‐stable macroaggregate C and SOC concentrations were observed among N fertilizer doses. Overall differences in water‐stable macroaggregates between sampling dates were greater than differences between fertilization treatments. Our study demonstrates that, in the short‐term, the use of organic or mineral N fertilizers hardly improves the stability of the macroaggregates and their C protective capacity when NT is performed. This finding could be related to the limitations imposed by water in the Mediterranean areas and the buffering effect of long‐term NT adoption on soil aggregate stability and C protection.