The impact of five different nets—conventional black, grey, white, and photoselective red and yellow—on the performance of “Gala Redlum” apples was evaluated over a five-year period (2020–2024) and compared to an uncovered control. The cumulative production over this period, ranked from highest to lowest, was as follows: white net (182.4 t/ha), grey net (178.5 t/ha), yellow net (175.8 t/ha), black net (175.5 t/ha), red net (169.5 t/ha), and uncovered control (138.8 t/ha). Vegetative growth results were inconsistent among the studied years. The cumulative photosynthetic rate (An) was slightly higher under the white net (57.9 µmol m⁻² s⁻¹). Fv/Fm values remained closest to optimal levels under the black and grey nets. Netting effectively protected fruits from elevated temperatures, particularly under the grey net, and reduced sunburn damage, with the grey, black, and yellow nets performing best in this regard. Overall profitability was increased by netting: the black net provided the highest cumulative income per hectare over a five-year period (EUR 72,315) alongside the second-lowest sunburn loss (0.69%), while the yellow net also showed strong economic performance (€64,742) with a moderate sunburn loss (1.26%) compared to the red net. Fruit dry matter and soluble solids content (SSC) were generally higher in the uncovered control, whereas °Hue values tended to be higher under the red and yellow nets. In summary, the black and yellow nets provided more balanced microclimatic conditions that enhanced tree performance, particularly under heat stress, leading to improved yield and profitability. However, the economic feasibility of each net type should be evaluated in relation to its installation and maintenance costs.

The MOPLUS project, funded by the Portuguese Recovery and Resilience Plan (PRR), aims to enhance soil organic matter, soil structure, and water retention in apple orchards located in the “Maçã de Alcobaça” Protected Geographical Indication area through organic fertilization based on locally available livestock effluents, thereby reducing reliance on synthetic fertilizers under Mediterranean climatic conditions. This study evaluated the physiological and biometric responses of apple trees subjected to four fertilization strategies (M1–M4) in three commercial ‘Gala’ orchards in central Portugal over three growing seasons (2023–2025). Measurements included leaf functional traits, gas exchange, chlorophyll fluorescence, spectral indices, vegetative growth, fruit production per tree and mean fruit weight. Interannual climatic variability and orchard-specific conditions were the dominant drivers of tree response, while fertilization effects were smaller and mainly expressed through interactions with year and orchard. When analyzed within the same orchard, fertilization strategies M2 and particularly M3 maintained physiological performance, vegetative growth, and fruit production per tree at levels comparable to full mineral fertilization. Among treatments, M3 showed the most consistent responses across sites and years, indicating that partial mineral substitution with pig slurry can sustain tree functioning while maintaining or enhancing fruit production per tree. The most restrictive strategy (M4) occasionally showed reduced photosynthetic performance under specific orchard–year combinations, suggesting a threshold effect associated with stronger mineral reduction, but without evidence of generalized physiological stress. Overall, these findings demonstrate that partial substitution of mineral fertilizers by organic amendments—especially pig slurry (M3) and, to a lesser extent, composted cattle manure (M2)—is agronomically viable, allowing apple tree performance and productivity to be maintained while enhancing system resilience under Mediterranean climatic variability. These results also provide practical decision support for site-adapted fertilization management in commercial drip-irrigated apple orchards, supporting reduced mineral fertilizer dependence without compromising productivity.

Protective net systems are increasingly used in Mediterranean apple orchards to mitigate climate-related production risks, yet their long-term agronomic and economic performance remains insufficiently documented. This study evaluated five protective net systems (black, grey, white, red, and yellow) and an uncovered control over six consecutive growing seasons (2020–2025) in a Mediterranean ‘Fuji’ apple orchard. Vegetative growth, reproductive development, yield, fruit quality, sunburn incidence, and economic performance were assessed under contrasting seasonal conditions. Yield ranged from 27 to 69 t ha⁻¹ and was strongly correlated with fruit number per tree (r = 0.90, p < 0.001), whereas net type did not significantly affect fruit number, mean fruit weight, or yield. Black nets reduced predicted sunburn incidence by 64% relative to the uncovered control (from 25.7% to 9.3%), promoted the greatest cumulative annual shoot growth (39.4 m tree⁻¹), and achieved the highest average final revenue among the evaluated treatments (€28,038 ha⁻¹ yr⁻¹). Under two assumed hail-damage scenarios (moderate and severe), estimated payback periods for the black net were 3.1 and 1.8 years, respectively. Overall, black nets combined the lowest predicted sunburn incidence, the greatest cumulative shoot growth, and the highest mean final revenue among the evaluated treatments, while yields remained comparable to the uncovered control, suggesting that they may represent a promising climate-adaptation strategy for Mediterranean ‘Fuji’ apple orchards.

Mediterranean apple orchards are increasingly exposed to high solar radiation, elevated temperatures, and recurrent summer droughts. This study evaluated the long-term responses of ‘Fuji’ apple trees to five protective net systems (Black, Grey, White, Red, and Yellow) and an uncovered control over five consecutive growing seasons (2020–2024). Leaf gas exchange was analyzed using linear mixed-effects models, whereas chlorophyll content index (CCI), chlorophyll fluorescence, and spectral reflectance indices were analyzed using factorial analysis of variance (ANOVA) or mixed-effects models, depending on the response variable and model estimability. Specific leaf area (SLA) was analyzed descriptively because the sampling procedure did not retain tree-level identity. CCI, Normalized Difference Vegetation Index (NDVI), and Photochemical Reflectance Index (PRI) showed variation associated with net treatment, while gas exchange was driven primarily by interannual climatic variability and chlorophyll fluorescence mainly by season during the 2022–2024 quantitative assessment period. Leaf surface temperature and photosynthetically active radiation (PAR) measurements further characterized differences in the environmental conditions associated with the net systems. Overall, the results indicate that interannual climatic variability was a major source of variation in physiological responses, whereas differences among net environments were more evident for leaf structural and spectral traits than for instantaneous gas exchange and chlorophyll fluorescence. These findings highlight the potential of protective net systems to modify the radiation and thermal environment and to be associated with long-term structural and physiological responses while also emphasizing the need for replicated net structures and treatment-specific microclimate measurements in future studies.