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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]

This study focuses on the quantification of soil water storage and crop yield under different tillage systems in dryland semiarid Mediterranean conditions. Three long-term tillage experiments based on cereal production were initiated in 1987, 1990 and 1992, at three different locations in the Ebro river valley (NE Spain): El Canós, Selvanera and Agramunt, with an increasing degree of aridity. Different tillage intensities were compared in each experiment using different implements: no tillage (NT), minimum tillage (MT), chisel (Ch), subsoiler up to 25 cm depth (Sub-25) and up to 50 cm (Sub-50), and mouldboard plough (Mb). Soil water content (SWC) up to 100 cm, soil water storage (SWS), precipitation storage efficiency (PSE) and crop yield were quantified during 8 (El Canós) and 19 years (Selvanera and Agramunt). The use of MT (at Selvanera) and NT (at El Canós and Agramunt) led to the highest SWC after the storage period (i.e., from previous harvest to crop tillering), with a major role played by the storage of water at deep soil layers. At Agramunt, Mb presented the lowest SWS when compared to Ch, Sub-50 and NT, and, consequently, the lowest post-tillering evapotranspiration. On the contrary, no differences were found between tillage systems on SWS at El Canós or at Selvanera. Significant yield differences were found at Agramunt being: NT > Sub-50 > Ch = Mb. These differences were especially important in years with mean yield below 2000 kg ha −1 , in which NT obtained the highest productions. At Selvanera yield was greater under conservation tillage (NT, MT) than under intensive tillage (Sub-50). Contrarily, no yield differences were found between tillage systems at El Canós, the site with the lowest water deficit, where crop residues were removed. A strong linear relationship was found between SWS and yield at Agramunt and Selvanera. At Agramunt the relationship presented a greater slope under Mb. In this site, in years with previous harvest-to-tillering SWS below 100 mm and with precipitation over 100 mm between tillering and anthesis, yields were, as an average, 1245 kg ha −1 higher than in standard years. This study demonstrates that under semiarid rainfed conditions, soil water storage increases with the use of conservation tillage systems, being amplified with the degree of aridity of the site. The relationship between water stored in the soil and crop yield and its reliability is site-specific. Once determined, it could be used to predict yield at the end of the vegetative phase of the crop to help take management decisions. [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]

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]

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 m 2 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 75 kg N ha −1 rate applied as top-dressing. A significant nitrate accumulation in the soil over the experimental period was observed under CT. Greater barley water use efficiency for yield (WUEy), N uptake and grain N content were found under NT than CT in three of the four cropping seasons studied. Moreover, for a given N rate, the use of organic fertilization increased significantly the WUEy as an average of CT and NT. When CT was used, a greater NHI was observed when using pig slurry compared with mineral N as an average of the four years studied. However, the use of different N fertilization treatments (rates or types) under CT or NT did not increase the NUE compared with the control. Our study demonstrates that the use of NT and the application of agronomic rates of N as pig slurry leads to greater barley yield and water- and nitrogen-use efficiencies than the traditional management based on CT and mineral N fertilization. [ABSTRACT FROM AUTHOR]