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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]

Maize is one of the main irrigated crops in northern Spain. However, the traditional cropping system used for its cultivation has relied on intensive monoculture, demanding significant inputs, and resulting in occasional unprofitable yields. A promising practice to increase the sustainability of farms is the use of double-cropping systems. The aim of this study was to evaluate the combined impact of introducing a legume prior to maize, together with different tillage systems and mineral N fertilization rates on crop yields and water productivity under Mediterranean irrigation conditions. The study compared monocropping maize (MC) versus legume-maize double cropping (DC) with three tillage systems (conventional tillage, CT; minimum tillage, MT; no-tillage, NT), and three mineral N fertilization rates (zero, medium and high). The legumes employed were pea for grain (2019), vetch for green manure (2020), and vetch for forage (2021). The highest yields were found in DC. On the one hand, the benefits associated with legume cropping allowed for increased grain yield of DC maize; on the other hand, the combined biomass of the legume plus maize led the DC systems to achieve significantly higher total biomass (sum of grain and stover) than the MC systems. In addition, a better adaptation of the maize DC phenological cycle to environmental conditions favoured higher yields in this system. Higher water consumptions in DC systems resulted in lower yield water use efficiency (WUE y). However, when only irrigation water was taken into account, DC was the system with the highest irrigation water use efficiency for yield (IWU y). Similarly, the high biomass values generated in the DC system resulted in higher water use efficiency for biomass (WUE b). The tillage system with the highest yields was NT. These results, together with a higher water retention capacity in NT made the water productivity (WUE b , WUE y and IWU y) of these systems higher. The use of high N fertilizer rates did not show any yield or WUE advantage over the medium rate. The results of this study indicate that in Mediterranean agroecosystems, the use of legume-maize double cropping systems together with NT systems and reduction of N fertilization can be a good strategy to maintain crop yields, while saving N fertilizer, and to improve WUE b and IWUE y. [ABSTRACT FROM AUTHOR]