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Under Mediterranean rainfed areas, no-till cereal-based systems have been adopted to cope with water availability and increasing input costs. However, the increased risk of biotic stresses, high N-fertilizer dependence, and current EU policies warrant cropping systems re-design. Evaluate diversification and N fertilization as strategies to improve N use efficiency at the cropping system level and quantify its productivity. Four crop sequences combined with four levels of N fertilization were assessed in a three-year field experiment in semiarid rainfed north-eastern Spain. Crop sequences were continuous winter wheat (WCS) and three-year diversified rotations with pea (PCS), faba bean (FCS), or a multi-service cover crop (MSCS) and two years of cereals. Crop, pre-crop and cropping system levels were considered. Agronomic evaluation included crops above-ground biological N fixation (Ndfa), net N balance (Ndfa minus N removed by grain), soil N mineralisation productivity, energy to N tradeoff (ENT), and N use efficiency of protein (NUEp) production. Pea yields ranged from 0 to 766 kg ha−1 and Ndfa from 24% to 54%. Faba bean yield ranged from 1378 to 4251 kg ha−1 and Ndfa from 32% to 72%. Net N balance was close to neutral for pea while in faba bean it ranged from 41 to −21 kg N ha−1. Alternative pre-crops led to greater soil N mineralisation (51 kg N ha−1, on average) and higher wheat yield (564 kg ha−1, on average) compared to wheat as the pre-crop. N fertilization increased protein yields, with FCS presenting the highest yields at all N fertilizer rates. This effect led to a stable NUEp (1.69 kg protein kg N supply−1), as the protein yield increased proportionally to N supply. Diversification improved the succeeding wheat performance and grain legumes N fixation exceeded grain N removal. Introducing legumes into cropping systems led to a decrease in energy productivity compared to the cereal-based system. However, protein production in the FCS was higher than in any other cropping system regardless of the N fertilizer rate. Crop diversification adds challenges and risks in dry Mediterranean areas. However, the study shows that crop diversification with faba bean can decrease cropping system's N-fertilizer dependence and increase protein productivity, contributing to cropping systems' sustainability. • Effect of crop diversification and N fertilization to support N efficient cropping systems. • Multiscale assessment including crop, pre-crop and the cropping system level. • Pea and faba bean supported cropping systems N use efficiency through biological N fixation. • Faba bean cropping system showed the greatest protein yields regardless of the N fertilizer rate. [ABSTRACT FROM AUTHOR]

The EU aims to improve plant protein production profitably and sustainably with a range of grain legumes suitable to different climatic conditions. Soybean (Glycine max Merrill) could be one important focus as the crop is adapted to diverse conditions and has the highest protein content per kg of grain. Under Mediterranean irrigated conditions, soybean presents a high-yielding potential, either as an annual single crop (SCS) or as part of a sequential double cropping system (DCS) following a winter crop. However, the lack of experimental data and knowledge in some southern areas like Spain, led to the use of rather early maturity groups (referring to experiences from more northern and eastern areas) that are underperforming in southern latitudes (i.e. < 42° N). The aims were to (i) explore later soybean maturity groups than currently used for SCS and DCS and (ii) quantify the drivers of their performance under Mediterranean irrigated conditions. A field experiment was carried out in NE Spain (2019, 2020 and 2021) in a split-plot design with four replications. In the main plots, SCS and DCS sowing dates were tested. In the sub-plots, 8–13 cultivars were tested per year covering MG from early 00 to late III. Five biomass sampling dates during soybean development were performed to fit a growth curve for every MG and sowing date. Grain yield, grain protein content, grains m−2, thousand-grain weight, 1st pod height and biological N fixation were measured at physiological maturity. The growth curve asymptote showed the strongest correlation with the soybean grain yield (r = 0.95) and the number of grains m−2 (r = 0.88). Consistent higher yields for MG II and III (4476 and 5314 kg ha−1, respectively) were found in the SCS and DCS compared to earlier MG. Grain protein concentration was reduced in the later MG but in all cases exceeded 40 g 100 g−1. In the DCS, a grain yield reduction of 25 % compared to SCS was observed, mainly caused by fewer grains m−2. Biological N fixation was low (30 g 100 g−1, on average), resulting from high residual soil N. In the SCS, the use of later MG (II and III) increases soybean yields. However, further research exploring MG III or later would better define soybean potential in these systems. While the agronomic performance of late MG (II and III) in the DCS was promising, technical aspects such as later harvesting date (moisture, pod shattering, etc.) or a slight reduction in grain protein concentration (although still above 40 g 100 g−1) should be considered. Our study proposes a shift towards the use of later soybean MG for Mediterranean irrigated cropping systems as a strategy to improve its competitiveness and, likely, farmer's adoption. This study highlights the potential to expand soybean production towards Mediterranean irrigated areas with a high yield potential. • Later soybean maturity groups were explored for Mediterranean single and double cropping systems. • Soybean performance in a single cropping system can be improved with later MG (II and III). • The use of later MG in a double cropping system increased yields but can complicate harvest. • Reliance on biological N fixation was generally low (below 30 g 100 g−1). [ABSTRACT FROM AUTHOR]

Over the last decades, non-cereal crops have been displaced in European cropping systems leading to a significant dependency on imported soybean. Continuous maize cropping under Mediterranean irrigated conditions can lead to agronomic and environmental problems. The objective of this work was to assess diversified Mediterranean irrigated cropping systems to maximize protein production while reducing synthetic N fertilizer use. A field experiment was carried out from 2019 to 2021 in an irrigated area in NE Spain. Four cropping systems, (i) continuous maize (MM), (ii) soybean in a rotation one out of three years (MSrt), (iii) barley-maize double cropping system (BM), and (iv) barley-soybean double cropping system (BS) were assessed at the crop, pre-crop and cropping system level. Productivity in terms of grain, energy and protein yield was measured at the crop and calculated for the cropping system level. As well, synthetic N fertilizer use efficiency was calculated for each cropping system. At the pre-crop level, soybean introduction led to a 28% yield increase in the following cereal (maize or barley) mainly due to the residual N effect. At the cropping system level, soybean in rotation (MSrt) did not lead to a significant increase in total protein production compared to MM (from 895 to 947 kg ha−1 yr−1), but it mildly increased synthetic N fertilizer use efficiency. Protein production in the BS system (1778 kg protein ha−1 yr−1) was significantly higher than in all other cropping systems (990 kg protein ha−1 yr−1 on average). As well, BS was the cropping system with the highest synthetic N fertilizer use efficiency compared to the other cropping systems (251 and 88 kg grain kg synthetic N fertilizer−1). Our results demonstrate that introducing soybean as a double crop following barley is a successful strategy to reduce environmental impacts resulting from N fertilizer use and increase protein production, contributing to plant protein self-sufficiency and cropping systems diversification. • Four cropping systems were assessed at the crop, pre-crop and cropping system level. • Soybean introduction in single cropping systems did not increase protein yield. • Soybean pre-crop effect increased the following cereal yields by 28%. • Barley-soybean double cropping increased protein yield at the cropping system level. • Synthetic N use efficiency was highest in barley soybean double cropping system. [ABSTRACT FROM AUTHOR]

Intercropping has gained attention as a strategy to diversify cereal-based systems and enhance sustainability. However, its performance in Mediterranean conditions, especially in non-organic farming, remains less explored. Assess the performance of intercropping under contrasting nitrogen (N) fertilisation levels to enhance productivity in the Mediterranean region. Three intercropping (IC) systems were compared with their respective sole crops under on-farm irrigated conditions in the Ebro Valley (NE Spain). The mixtures included rapeseed/pea (IC-RP) and durum wheat/pea (IC-WP) over three seasons from 2021 to 2023, and durum wheat/faba bean (IC-WF) in 2022 and 2023. A row intercropping design was set at a 50/50 replacement ratio, with two N fertilisation treatments: 0 N (no mineral N) and +N (75 kg mineral N ha−1, with additional pre-sowing fertilisation with pig slurry applied at 165 kg N ha−1 in 2023 only). Key variables included grain yield, land equivalent ratio (LER), overyielding index, biomass and N concentration. The IC-WP and IC-WF showed reduced legumes yields due to competition, with no overyielding or increased land use efficiency (LER=0.94 and 0.86, respectively). In contrast, IC-RP exhibited increased land use efficiency (LER=1.43), though with high variability, and achieved overyielding (+9 %) in only one out of the three years. Intercropping productivity in Mediterranean areas depends heavily on species selection. Pairing species with different physiology, like rapeseed and pea, promotes temporal niche differentiation and compensation mechanisms. Conversely, closer-matched species like wheat and legumes tend to intensify competition, reducing benefits. Several indicators are necessary to assess intercropping performance. Rapeseed-pea intercropping warrants deeper exploration in Mediterranean conditions. • 3 intercropping systems were studied in on-farm irrigated conditions for 2–3 years. • Wheat-legume land use efficiency was similar to or lower than respective sole crops. • Rapeseed-pea increased land use efficiency 2 out of 3 years compared to sole crops. • Varying species phenology and architecture favour compensation mechanisms. • Multiple indicators must be considered to fairly assess intercrops. [ABSTRACT FROM AUTHOR]

Mediterranean cropping systems, characterised by continuous cereal cropping, are largely dependent on synthetic inputs, such as N fertilisers. On the other hand, they face difficult pedoclimatic conditions, exacerbated by climate change. Diversification is seen as a way to increase cropping systems resilience. The aim of this study was to co-design diversified cropping systems based on the expertise of local stakeholders and co-assess their performance, using modelling data. Our case study is the Ebro valley in Spain, a Mediterranean area with great potential for diversification, particularly where irrigation is available. Two workshops were organized to i) define the reference system in the study area and its limitations ii) co-design diversified systems to overcome these limitations and iii) co-assess reference and diversified systems. Between the two workshops, the STICS soil-crop model was calibrated with local experimental data, enabling to simulate the inter-annual (2000–2021) agronomic and environmental performance of the reference and diversified systems. An economic analysis was conducted. Stakeholders evaluated all economic, agronomic and environmental aspects. The reference system was a continuous winter cereal crop based on synthetic N fertilisation and intensive tillage. The four diversified co-designed systems consisted in introducing pea and/or rapeseed every 2 or 4 years, reducing tillage and partially replacing synthetic N fertilisation with locally sourced livestock manure. Simulation results showed that wheat and barley grain yields remained stable with diversification. Pea and rapeseed yields were lower in rotations where both were introduced compared to when each was the only break crop over 4 years. At the system level, protein yield remained stable with diversification, however, energy yield decreased by 20 % when break crops were introduced twice and by 10 % when introduced once. Gross margins improved with diversification only when pea was introduced once (12 %), mainly due to reduced expenses (-31 %), while incomes remained stable compared to RCS. However, incomes decreased by 5 % when rapeseed was introduced once, and by 10 % when both break crops were introduced. Unexpectedly, environmental performance deteriorated with diversification, with increased N losses through ammonia volatilisation and nitrate leaching in the years following pea and rapeseed cropping, due to greater N availability in the soil. An increased use of pesticides was predicted by the stakeholders in diversified systems, where the environmental impacts were exacerbated with the higher presence of break crops. The reference system presented slightly lower N availability and increased soil organic carbon storage. Overall, the approach proved useful in identifying a diversification strategy that improved agronomic and economic performance, with the system including pea once every four years being the most efficient. However, the environmental trade-offs associated with the increased presence of pea and rapeseed in the crop rotation must be considered in order to mitigate the environmental risks. • Participatory workshops and modelling were combined to assess diversification. • Introducing pea and rapeseed maintain protein yield but decreased energy yield. • Continuous cereal was the most efficient in raising long-term soil organic carbon. • Gross margin increased only when introducing pea once in a 4-year rotation (+12 %). • Diversified cropping systems increased N availability and risk of losses. [ABSTRACT FROM AUTHOR]