Search Results (315)

Agrivoltaics is a rapidly expanding technology thanks to its energy, agronomic, and microclimatic benefits, which have been demonstrated in a variety of climatic contexts around the world. This study presents the first systematic review exclusively focused on experimental agrivoltaics field studies, based on the analysis of 82 peer-reviewed articles. The aim is to provide a cross-study comparable synthesis of how shading from different photovoltaic (PV) technologies affects microclimate, crop yield, and crop quality. The reviewed systems include four main categories of PV modules: conventional, bifacial, semi-transparent/transparent, including spectrally selectivity modules and concentrating photovoltaic systems (CPV). To handle heterogeneity and improve comparability, results were normalised against open-field controls as relative percentage variations. The analysis reveals a high variability in results, strongly influenced by crop type, climate, level of shading, and reduction in PAR (Photosynthetically Active Radiation). Studies conducted with the same shade intensity but under different climatic conditions show contrasting results, suggesting that there is no universally optimal agrivoltaics configuration. Nevertheless, the review allows us to identify recurring patterns of compatibility between crops and photovoltaic technologies, providing useful guidance for choosing the most suitable technology based on climate, crop physiology, and production objectives. Full article

Monitoring stem sap flow is essential for understanding plant water-use strategies and eco-physiological processes in the ecologically fragile karst region. In the study, we continuously monitored four co-occurring species—Cryptomeria japonica var. sinensis (LS), Liquidambar formosana (FX), Camptotheca acuminata (XS), and Melia azedarach (KL)—using the thermal dissipation probe method in a karst farmland-to-forest restoration area. We analyzed diurnal and nocturnal sap flow variations across different growth periods and their responses to environmental factors at an hourly scale. The results showed (1) A “high daytime, low nighttime” sap flow pattern during the growing season for all species. (2) The proportion of nocturnal sap flow was significantly lower in the growing than in the non-growing season. (3) Daytime sap flow was primarily driven by photosynthetically active radiation (PAR) and vapor pressure deficit (VPD) during the growing season. In the non-growing season, daytime drivers were species-specific: relative humidity (RH, 39.39%) for LS; air temperature (Ta, 23.14%) for FX; PAR (33.03%) for XS; and soil moisture at a 10 cm depth (SM1, 25.2%) for KL. Nocturnal flow was governed by VPD and RH during the growing season versus soil moisture (SM1 and SM2) and RH in the non-growing season. These findings reveal interspecific differences in water-use strategies and provide a scientific basis for species selection and afforestation management in the karst ecological restoration of this research area. Full article

Strip intercropping improves productivity through enhanced light interception. In this study, we quantified the effects of strip width on light interception of soybean across six strip widths (2.2 m, 2.5 m, 2.8 m, 3.1 m, 3.4 m, 3.7 m) when intercropped with maize. Results showed that photosynthetically active radiation (PAR) in western rows of intercropped soybeans peaked at 11:30 a.m., whereas in eastern rows, it occurred at 1:00 p.m. Across 2.2 m to 3.7 m, PAR in the western rows of intercropped soybeans was 6.1% higher than that of the eastern rows for the whole growth period. During the R5 stage, compared to eastern rows, radiation use efficiency (RUE), dry matter accumulation, and leaf area of soybean in western rows increased by 4.0%, 7.4%, and 6.7%, respectively. Compared to the 2.2 m strip width, grain yields in eastern rows of 2.5–3.7 m strip widths were 8.5%, 54.7%, 56.5%, 63.4%, and 69.0% higher than those of the 2.2 m strip width, respectively. PAR had the strongest influence on dry matter and leaf area at a 3.7 m strip width, while RUE had the strongest influence at 3.1 m strip widths. These findings advance our understanding of light partitioning in strip intercropping and support future climate-adaptive intercropping systems’ modeling. Full article

Microalgae are photosynthetic microorganisms capable of fixing CO₂ to produce O₂ and a wide variety of metabolites of interest. Attempts have been made to describe their growth dynamics using mathematical models; however, these models fail to fully represent the dynamics of this bioprocess. Therefore, achieving maximum biomass production in the shortest possible time represents a control challenge due to the nonlinear and time-varying dynamics. Some classic control strategies implemented for this bioprocess are totally or partially dependent on a mathematical model, resulting in controllers with low performance, implementation complexity, and limited robustness. This is where the Virtual Reference Feedback Tuning (VRFT) approach becomes relevant, as it is a model-free control strategy. VRFT is based on the iterative generation of a virtual reference with the aim of minimizing steady-state error, without requiring an explicit model of the bioprocess. Its implementation involves the collection of experimental data in open loop, the minimization of a cost function in closed loop, and the linearization of the system around a stable equilibrium point. This work presents the design and implementation of a VRFT-based control strategy applied to the closed cultivation of the microalga Scenedesmus obliquus UTEX 393 in three flat photobioreactors at laboratory scale. The variables controlled using this strategy were temperature, photosynthetically active light intensity, and level. The experimental results showed that the pre-established references were met. A steady-state temperature of 25 ± 0.625 °C, a PAR (Photosynthetically Active Radiation) light intensity of 100 ± 5 µmol·m⁻²·s⁻¹, and level control that ensured a constant volume of the culture medium were achieved. This suggests that VRFT is a viable control alternative for this type of bioprocess under nominal conditions. Full article

Agrivoltaics integrates photovoltaic (PV) power generation with agricultural practices, enabling dual land-use and mitigating land-use competition between agriculture and energy production. China has 3.43 million hectares of tea fields, offering significant potential for PV-integrated tea plantations (PVtea) to address land scarcity in clean energy development. This study aimed to investigate the impact of PV modules above tea bushes in PVtea on the yield and quality of tea, as well as tea plant resistance to environmental stresses. The PV system uses a single-axis tracking system with a horizontal north–south axis and ±45° tilt. It includes 70 UL-270P-60 polycrystalline solar panels (270 Wp each), arranged in 5 columns of 14 panels, spaced 4500 mm apart, covering 280 m². The panels are mounted 2400 mm above the ground, with a total capacity of 18.90 kWp (656 kWp/ha). Tea yield, quality-related components, leaf photosystem II (PSII) activity, and plant resistance to environmental stresses were investigated in comparison to an adjacent open-field tea plantation (control). The mean photosynthetic active radiation (PAR) reaching the plucking table of PVtea was 52.9% of the control, with 32.0% of the control on a sunny day and 49.0% on a cloudy day, accompanied by an increase in ambient relative humidity. These changes alleviated the midday depression of leaf PSII activity caused by high light, resulting in a 9.3–15.3% increase in leaf yield. Moreover, PVtea summer tea exhibited higher levels of amino acids and total catechins, resulting in tea quality improvement. Additionally, PVtea enhanced the resistance of tea plants to frost damage in spring and heat stress in summer. PVtea integrates photovoltaic power generation with tea cultivation practices, which not only facilitates clean energy production—an average annual generation of 697,878.5 kWh per hectare—but also increases tea productivity by 9.3–15.3% and the land-use equivalence ratio (LER) by 70%. Full article

The Daily Light Integral (DLI) maps of Portugal are decision-support tools to provide objective assessments of light availability for plants. These maps allow for the analysis of the spatial and seasonal distribution patterns of photosynthetically active radiation (PAR, 400–700 nm). A semi-automatic DLI mapping workflow was elaborated and DLI maps with two different scales (2 and 5 mol·m⁻²·d⁻¹) were created for Portugal’s mainland, analyzing from regional (Northern regions, Central regions, Southern regions) and seasonal (Spring, Summer, Autumn, Winter) perspectives. The DLI values and ranges in Portugal provide a clear spatial gradient from north to south, influenced by geographic location, topography, and climate. In autumn, the DLI values decrease (11–41 mol·m⁻²·d⁻¹) and the lowest DLI values are observed in the winter months (7–17 mol·m⁻²·d⁻¹). During spring, DLI values increase, reaching their peak in the summer months (41–57 mol·m⁻²·d⁻¹). In autumn the DLI range is narrow (11–13 mol·m⁻²·d⁻¹), as well as in winter (8–12 mol·m⁻²·d⁻¹), and it becomes broader during spring and summer (11–14 mol·m⁻²·d⁻¹). To enhance agricultural practices, future DLI maps should be integrated with agro-climatic maps and thematic layers such as soil, water, topography, temperature, and biodiversity. These integrated maps should then be incorporated into agricultural policy and decision-making to improve crop management strategies. Portugal’s agricultural lighting strategy will utilize DLI maps alongside crop-specific recommendations, shading management, local conditions and market demands. Full article

Combining leaf gas exchange with chlorophyll fluorescence, this study quantified the effects of soil water content (SWC) on mesophyll conductance (g_m) and biochemical parameters in 8-year-old pear trees across three soil textures [clay (CS), sandy (SS), loam (LS)], each subjected to three irrigation levels (100%FI, 75%FI, 50%FI). Results showed that SWC differed significantly, with CS > LS > SS, and that the difference in SWC in loam soil was the most obvious among different irrigation levels. The leaf water content (LWC) of SS was higher than that of LS and CS, and SS_50%FI showed 7.53% and 13.30% greater LWC compared to LS_50%FI and CS_50%FI, respectively. Specific leaf area (SLA) peaked at CS_75%FI and SS_100%FI. Soil texture and irrigation level had significant interactive effects on g_m, the product of light absorption coefficient and light energy partitioning ratio (α·β), leaf apparent CO₂ compensation point, dark respiration rate under light, and photosynthetic biochemical parameters. Differences in the values of α·β among the nine treatments were significant and the maximum values in the three soil textures were 0.660 (LS_75%FI), 0.366 (SS_100%FI) and 0.462 (CS_50%FI), respectively. The most sensitive treatment of g_m, responding to photosynthetically active radiation (PAR), was SS_100%FI and the maximal g_m under saturated PAR reached 0.271 molCO₂·m⁻²·s⁻¹, increasing 2.2-fold and 8.8-fold compared to that of SS_75%FI and SS_50%FI, respectively. An underestimation of 26.4% to an overestimation of 30.3% for g_m and an underestimation of 28.8% to an overestimation of 15.5% were observed for biochemical parameters if the empirical value (0.425) of α·β was adopted. Our findings indicated that the maximum leaf g_m could be obtained at 75%FI for loam soil, 100% FI for sandy soil, and 50% FI for clay soil, respectively. Full article

Climate change is driving urgent demand for resilient crop varieties capable of withstanding extreme and changing conditions. Identifying resilient varieties requires systematic plant phenotyping research under controlled conditions, where dynamic environmental impacts can be studied. Current growth cabinets (GC) provide this capability but remain limited by high costs, static environments, and scalability. These limitations pose a challenge for climate change-based phenotyping research which requires large-scale trials under a variety of dynamic climate conditions. Presented is a microclimate-controlled smart growth cabinet (MCSGC) platform, addressing these limitations through four innovations. The first is dynamic microclimate simulation through programmable environmental ‘recipes’ reproducing real climactic variability. The second is interconnected scalable multi-cabinet for parallel experiments. The third is modular hardware able to reconfigure for different plant species, remaining cost-effective at <$10,000 AUD. The fourth is automated data collection and synchronisation of environmental and phenotypic measurements for Artificial Intelligence (AI) applications. Experimental validation confirmed precise climate control, broad crop compatibility, and high-throughput data generation. Environmental control stayed within ±2 °C for 97.42% while dynamically simulating Hobart, Australia, weather. The MCSGC provides an environment suitable for diverse crops (temperature 14.6–31.04 °C, and Photosynthetically Active Radiation (PAR) 0–1241 µmol·m⁻²·s⁻¹). Multi-species cultivation validated the adaptability of the MCSGC across Cannabis sativa (544.1 mm growth over 34 days), Beta vulgaris (123.6 mm growth over 36 days), and Lactuca sativa (19-day cultivation). Without manual intervention the system generated 456 images and 164,160 sensor readings, creating datasets optimised for AI and digital twin applications. The MCSGC addresses critical limitations of existing systems, supporting advancements in plant phenotyping, crop improvement, and climate resilience research. Full article

Agrivoltaic systems (AVS) are gaining global attention as an innovative solution to simultaneously address food, water, and energy security challenges. However, the effective design and management of these dual-use systems hinge on a comprehensive understanding of their microclimatic impacts. This systematic review critically analyzes the current literature on AVS microclimates, focusing on key atmospheric (air temperature, relative humidity, wind speed), radiation (Photosynthetically Active Radiation—PAR, global radiation, shading rate), and soil parameters (temperature, moisture). Results indicate that while reduced soil temperature and enhanced moisture retention are consistent and agronomically significant benefits, the effects on air temperature are highly variable. These often demonstrate site-specific warming or pronounced vertical thermal stratification. Furthermore, AVS significantly alters light availability, with PAR reduction ranging from 5% to 94%, emphasizing the system’s inherent spatial and temporal heterogeneity. A major gap identified is the lack of standardized measurement methodologies, limiting data comparability. To address this, we propose a “Minimum Viable Monitoring” (MVM) framework, advocating for multi-zone and multi-height sensor placement to accurately capture microclimatic variability. These findings highlight that the observed heterogeneity, rather than a limitation, presents a unique opportunity for precision agriculture and zoned management strategies. Full article

The red macroalga Porphyra plays a key role in Integrated Multi-Trophic Aquaculture (IMTA) systems, acting both as a biofilter and as a source of bioactive compounds (BACs) with nutritional and photoprotective value. This study evaluated how nitrogen source and concentration influence its physiological, photosynthetic, and biochemical responses under ultraviolet radiation (UVR). Gametophytes were cultured for four days under two nitrate sources (artificial and fishpond effluents) at 3 and 5 mM concentrations and exposed to PAR (120 µmol·photons·m⁻²·s⁻¹) and UVR (9 W·m⁻² for 6 h·day⁻¹). Morphological responses, photosynthetic performance, and BACs were quantified. Nitrate uptake increased with nitrate concentration, while growth rate remained unaffected. Samples grown with fishpond effluents, particularly at 3 mM, showed darker pigmentation and higher phycoerythrin and mycosporine-like amino acid (MAA) contents, indicating enhanced nitrogen assimilation and photoprotective capacity. Conversely, 3 mM artificial nitrate in the water promoted the highest electron transport rate and lowest non-photochemical quenching, suggesting greater photosynthetic capacity. Polyphenols and antioxidant activity showed no significant differences among treatments, indicating similar stress status. Overall, it is suggested that fishpond effluents acted as a natural biostimulant, enhancing biliprotein and MAA synthesis without compromising physiological stability, reinforcing its potential for sustainable IMTA-based production of high-value photoprotective compounds. Full article

The role of customized DLI maps in optimizing lighting strategies for controlled and open field crop production is gradually increasing, resulting in the creation of specialized DLI maps for more countries. Daily Light Integral (DLI) [mol·m⁻²·d⁻¹] is an accumulation or integration of quantum flux measurements per second over one day (24 h), its spatial distribution will be visualized on maps. Our research objectives are: (1) to create 1 mol·m⁻²·d⁻¹ resolution Slovakia DLI map and explore the seasonal and regional characteristics, (2) to create 2 and 5 mol·m⁻²·d⁻¹ resolution DLI maps to show how the spatial resolution capabilities change in a local (country) and regional (Europe) context, (3) to summarize and compare the seasonal patterns for mountainous and lowland areas with characteristic DLI values (minimum, maximum, average, range). The current study shows how much light was available at different times of the year using monthly DLI threshold maps for 1 mol·m⁻²·d⁻¹, 2 mol·m⁻²·d⁻¹, and 5 mol·m⁻²·d⁻¹. The data present a clear seasonal and regional pattern. In the seasons, the monthly total DLI maximum and minimum differences reached: 21 DLI units (38–17 mol·m⁻²·d⁻¹) in spring, 17 DLI units (46–17 mol·m⁻²·d⁻¹) in summer, 20 DLI units (26–6 mol·m⁻²·d⁻¹) in autumn, 9 DLI units (13–4 mol·m⁻²·d⁻¹) in winter. Slovakia is an East–West oriented country, which explains the use of the 1 mol·m⁻²·d⁻¹ DLI map. DLI maps are of particular importance for plant cultivation technologies that are sensitive to the amount of light and its temporal and spatial distribution, such as greenhouse vegetables or certain fruit species. Spatial DLI data support lighting strategy and design, supplemented by lighting, shading management, and photosynthetically active radiation (PAR) availability and efficient use. Full article

The field experiment aimed to evaluate the effect of different nitrogen rates on accumulation of aboveground dry mass (AGDM), leaves area index (LAI), and intercepted photosynthetically active radiation (iPAR) of pea (Pisum sativum L.) varieties. The experiment was arranged in a factorial randomized block design consisting of three levels of the first factor (variety) and seven levels of the second factor (NPK fertilization treatments were used: (1) NPK 0:0:0 (control), (2) NPK 0:40:80, (3) NPK 15:40:80, (4) NPK 30:40:80, (5) NPK 45:40:80, (6) NPK 15 + 15:40:80, (7) NPK 60:40:80). The growth indicators (LAI and AGDM) and iPAR were assessed three times during the growing season. Nitrogen fertilization positively influenced LAI, but significant differences in LAI were found only under splitted N30 (N15 + N15), N45, and N60 applications, compared to the treatment N0 P40K80. In the dry 2015 and the optimal moisture 2016, N30, N45, and N60 rates significantly increased AGDM. The influence of fertilization on iPAR varied between experimental years, and it was strongest in the dry 2015, when applying N15 + 15 and N60 fertilization significantly increased iPAR, compared to the control. According to LAI and iPAR data, pea varieties were ranked in descending order: Simona, Ieva DS, and Respect. LAI significantly (p ≤ 0.01) correlated with AGDM and iPAR, but the relationship weakened as peas reached later growth stages. These results provide valuable knowledge, and it will be useful for researchers in developing new cultivation methodologies to achieve higher semi-leafless pea productivity by applying different combinations of nutrition and new varieties. Full article

In eutrophic shallow lakes, dissolved oxygen (DO) exhibits significant temporal variations, regulated by the combined effects of photosynthesis and water temperature (WT). High-frequency monitoring enables a detailed capture of DO diel cycles, providing a more comprehensive understanding of the dynamic changes within lake ecosystems. This study involved high-frequency (10 min intervals) in situ monitoring of DO over a three-year period (2020–2022) in the littoral zone of Taihu Lake, China. Random forest regression analysis identified WT, photosynthetically active radiation (PAR), and relative humidity (RH) as the three most influential variables governing DO dynamics. The relative importance of these factors varied seasonally (0.117–0.392), with PAR dominating in summer (0.383), whereas WT had the highest importance in other seasons (0.312–0.392). Cusum analysis further revealed that the DO-WT relationship changed from a dome-shaped pattern in spring, autumn, and winter to a bowl-shaped pattern in summer, indicating that thermal stratification intensified oxygen gradients. In addition, the majority of DO recovery occurred in the late afternoon during summer, suggesting that severe oxygen consumption delayed the daytime accumulation of DO. Our findings emphasize the critical roles of photosynthesis, respiration, and abiotic factors in shaping DO dynamics. This research enhances our understanding of DO fluctuations in eutrophic shallow lakes and provides valuable insights for ecosystem management, supporting the development of effective strategies to prevent and mitigate hypoxia. Full article

Greenhouse horticulture is an energy-intensive production system that requires innovative solutions to reduce energy demand without compromising crop yield or quality. Functional greenhouse covers are particularly promising, as they regulate solar radiation while integrating energy-harvesting technologies. In this study, six nanostructured glass coatings incorporating semiconductor-based quantum dots (QDs) and quantum wires (QWs) of Ge and TiN are developed using magnetron sputtering—an industrially scalable technique widely applied in smart window and energy-efficient glass manufacturing. The coatings’ optical properties are characterized in the laboratory, and their agronomic performance is evaluated in greenhouse trials with lamb’s lettuce (Valerianella locusta) and radish (Raphanus sativus). Plant growth, yield, and leaf color (CIELAB parameters) are analyzed in relation to spectral transmission and the daily light integral (DLI). Although uncoated horticultural glass achieves the highest yields, several Ge-QD coatings provide favorable compromises by selectively absorbing non-photosynthetically active radiation (non-PAR) while maintaining acceptable crop performance. These results demonstrate that nanostructured coatings can simultaneously sustain crop growth and enable solar energy conversion, offering a practical pathway toward energy-efficient and climate-smart greenhouse systems. Full article

Observational studies in several regions and our dataset indicate changes in global solar radiation (R_S); here, we analyze how atmospheric conditions modulate its spectral composition. This study investigates the effects of atmospheric conditions on the spectral composition of global solar radiation (R_S) across different wavelength ranges: ultraviolet A (UVA), photosynthetically active radiation (PAR), and near-infrared radiation (NIR), using the ratios UVA/R_S, PAR/R_S, and NIR/R_S. A high-quality spectral irradiance dataset (300–1025 nm) covering eight years of observations from a representative rural site in Central Europe (Meteorological Observatory Lindenberg, Tauche, in North-East Germany) was used. The average values obtained for the ratios were 0.049 ± 0.010 for UVA/R_S, 0.433 ± 0.044 for PAR/R_S, and 0.259 ± 0.030 for NIR/R_S. Thus, the UVA range contributed approximately 5% to global radiation, PAR 43%, and NIR 26%. Strong correlations were found between each spectral component and R_S, with determination coefficients exceeding 0.90 in all cases, particularly for PAR. This suggests that, in the absence of direct spectral measurements, these components can be reliably estimated from R_S. A seasonal pattern was also identified, with maximum values in warmer months and minimum values in colder ones, most notably for PAR/R_S. In contrast, NIR/R_S exhibited an inverse pattern, likely influenced by atmospheric water vapor. A long-term decreasing trend in these ratios was also identified, being most pronounced in the UVA/R_S ratio. Additionally, atmospheric conditions significantly affected the spectral distribution of R_S, with UVA and PAR proportions increasing under specific conditions, while NIR remained more stable. Under overcast conditions, the ratios for shorter wavelengths (UVA and PAR) increased, indicating higher scattering effects, while NIR was less affected. Full article