The citrus processing industry generates large amounts of organic residues whose sustainable management is a major environmental challenge. The aim of this study was to evaluate the effects of incorporating citrus-derived waste (CW) into coconut-coir-based substrates on tomato (Solanum lycopersicum L., cv. Proxy) under different irrigation regimes (I) in a factorial design (CW × I) with three replications. Each replicate consisted of six plants (pots), and the replicate was considered the experimental unit. Plants were grown in substrates amended with 0%, 6.25%, 12.5%, 25.0%, and 37.5% (v/v) citrus waste and subjected to three water regimes (100%, 75%, and 50% of the standard water supply). Plant growth, biomass allocation, yield components, and fruit quality traits were assessed. Results indicate that CW can be incorporated into coconut-coir substrates without detectable penalties in total production at low-to-moderate rates (6.25–12.5%) across all irrigation regimes. Yield reductions of 18% (from 3398 to 2789 g plant⁻¹) attributable to CW were observed mostly at the highest inclusion rates under moderate deficit irrigation (75% water supply), whereas under severe deficit (50% water supply), production declined across all CW rates, including 0%, indicating that water deficit has a dominant limiting effect. Fruit quality parameters were generally maintained or improved in amended substrates, particularly under reduced irrigation with deficit irrigation, generally increasing total soluble solids at 100%, 75%, and 50% WC (+13%, +19%, and +9%, respectively). Overall, these findings support the use of citrus waste at low-to-moderate proportions as a sustainable amendment for soilless tomato cultivation without marked negative effects on yield and fruit quality, enabling its use as a locally sourced substrate component within circular-economy strategies.

Water scarcity is increasingly challenging greenhouse tomato production, particularly in Mediterranean and semi-arid regions where irrigation water availability is becoming progressively limited. This study evaluated whether a superabsorbent polymer (SAP) can support water-saving irrigation in tomato grown in coconut fibre. Plants were cultivated in pots under four irrigation amounts (100, 75, 50, and 25% of crop water requirement—WC) combined with two SAP levels (0 and 2 g L⁻¹). Irrigation was managed by a lysimetric control system. Reducing irrigation decreased total fruit yield (averaged across SAP treatments) from 100% WC (1212 g plant⁻¹) to 50–25% WC (914 and 624 g plant⁻¹, respectively), while non-marketable fruit number was unchanged (15.4 fruit plant⁻¹, on average). SAP increased total yield, averaged across irrigation treatments (from 925 to 1022 g plant⁻¹), and marketable fruit number (from 26.3 to 32.3 fruit plant⁻¹), without affecting unitary fruit weight (20.4 g fruit⁻¹, on average). SAP also increased net photosynthesis (from 16.0 to 17.4 µmol CO₂ m⁻² s⁻¹), while stomatal conductance (0.14–0.15 mol H₂O m⁻² s⁻¹) and WUE (4.0 µmol CO₂ mmol⁻¹ H₂O) were not affected by SAP. Total soluble solids increased under severe deficit (7.8 °Brix at 25% WC) and were enhanced by SAP (from 6.9 to 7.6 °Brix), while colour parameters were mainly driven by irrigation. Overall, the irrigation amount was the primary driver of performance. Moderate deficit irrigation (75% WC) maintained a marketable fruit number and total fruit weight comparable to full irrigation (100% WC). SAP amendment acted as a complementary tool to improve marketable production and net photosynthesis across irrigation levels, providing an additive benefit to crop productivity.

Intercropping rhizobia‐inoculated forage legumes in organic wheat systems reduces weed pressure and supplies nitrogen (N) to the companion crop via biological N ₂ fixation (BNF). However, adoption of combined intercropping and rhizobial inoculation remains limited. This 2‐year field study compared durum wheat ( Triticum turgidum L. subsp. durum (Desf.) Husn.), as a sole crop, or intercropped with forage legume ( Trifolium subterraneum L., Trifolium michelianum Savi, or Vicia sativa L.) in southern Italy. Legumes were rhizobia‐inoculated or non‐inoculated. Treatments were evaluated under reduced N fertilization (60 kg N ha ⁻¹ ) or standard N fertilization (120 kg N ha ⁻¹ ). The warmer and drier 2023/2024 season reduced wheat yields but increased grain protein, whereas the wetter 2024/2025 season enhanced yields, BNF (estimated using published empirical relationships linking N ₂ fixation to legume biomass yield and shoot N content), and wheat N recovery efficiency. Regardless of environmental conditions or agronomic treatments, wheat–legume systems consistently reduced weed biomass compared with sole wheat. Inoculated V. sativa and T . subterraneum improved wheat grain yield versus sole wheat, particularly under favorable conditions at reduced N rate. Vicia sativa exhibited the highest BNF, especially when inoculated at the low N rate, whereas T. michelianum showed smaller benefits. Inoculated T . subterraneum showed the highest nodule number and weight, and higher soil nitrate nitrogen (NO ₃ ⁻ ‐N), particularly at the higher N rate. Although results were context‐dependent on environmental conditions, legume living mulches integrated with effective rhizobial inoculation and reduced N fertilization support the agronomic sustainability of organic wheat systems in Mediterranean environments.