Impact Of Shading Research Articles

Effect of Partial Shading on a PV Array and Its Maximum Power Point Tracking Using Particle Swarm Optimization

The maximum power point (MPP) of a Solar Photovoltaic (SPV) array varies with temperature and irradiation. Shadow of various objects falling on a certain portion of the SPV array causes partial shading condition (PSC) which results in the formation of hot spot. Thus, reducing the power (output) by 33% on a single cell in addition to the occurrence of various peaks on a P-V curve. To detect global maxima among the multiple peaks is a challenge for researchers. Hence, different Maximum Power Point Tracking (MPPT) techniques are used to overcome this challenge. In this paper, the impact of partial shading on SPV array has been analysed and the Particle Swarm Optimization (PSO) based MPPT technique is used to obtain global maxima under partial shading conditions. The MPPT controller is incorporated with a converter (boost) to vary the input voltage as per the duty cycle of the switch generated by PSO algorithm-based controller.

A methodology for prediction and assessment of shading on PV systems

Frequently, PV systems are affected by dirt, dust or shadowing from surrounding elements, such as trees and buildings. The shadows can cause partial shading conditions, when the irradiance is not uniform on PV installation, which lead to losses of power. Thus, the shadow prediction is primordial for a better output power estimation and to minimize its losses. The aim of this article is to propose a methodology using intuitive and available tools for shading prediction and losses assessment on PV installations. A study about the shadow pattern and module orientation (portrait and landscape) influence and an analysis of the shading losses on a PV plant were performed in order to demonstrate the applicability of the methodology. The shading effect is drastic when the shading is parallel to the short edge, whereas the effect is lower when it is parallel to the long edge. On the other hand, the losses due to shading and the difference in the position of the modules (landscape or portrait) have a lower impact on the photovoltaic plant case. It was concluded that the methodology is feasible and applicable for shading impact evaluation, despite limitations for large systems due to the simulation time.

Darkness and low-light alter reserve mobilization during the initial growth of soybean (Glycine max (L.) Merrill)

Light is both a source of energy and a developmental signal, and therefore has a major impact upon initial seedling growth. This is particularly the case for species where photosynthesis in the cotyledons makes a significant contribution to carbon balance. In addition to containing reserves of proteins, lipids and carbohydrates the cotyledons of soybean (Glycine max (L.) Merrill) maintain sufficient photosynthetic activity to counterbalance respiratory carbon loss. Based on the hypothesis that altered light regime would affect seedling photosynthesis and development, we investigated the impact of shading and darkness on the reserves present in different soybean seedling organs. Plants were grown until the VC/V1 stage under normal light conditions (500 µmol m−2 s−1, 12/12 h) before being divided into three groups; normal light, low light (50 µmol m−2 s−1, 12/12 h) and darkness. After 3 days plants were harvested at three time points over the course of a day/night cycle and seedling organs analysed separately. Low light and darkness led to partial etiolation and the consumption of carbohydrates and fatty acids in several organs. Effects on cotyledon reserve mobilisation were modest, as darkness and low light did not lead to decreased cotyledon mass. However, metabolism in the epicotyl was more strongly perturbed, with the accumulation of branched chain and aromatic amino acids together with sugars that may be required to drive organ elongation. Darkness also served to abolish diurnal alterations in starch and asparagine concentrations detected in control plants. Overall, the data reinforce the flexibility of seedling metabolism, revealing similarities to the responses of adult plants to carbon starvation .

Seaweed farming pressure affects seagrass and benthic macroalgae dynamics in Chwaka Bay (Zanzibar, Tanzania)

Farming of Eucheuma denticulatum is a major activity in Zanzibar affecting seagrass ecosystems primarily through shading and trampling. The aim of this study was to test the impacts of shading and trampling during seaweed farming on seagrass meadows composed by Halophila stipulacea and Thalassia hemprichii and their associated benthic macroalgae. Areas covered by these species were selected for the building of seaweed farms in three treatments: seaweed farm plots (with shading and trampling effects), trampling plots (with trampling effects only), and control plots (with no shading or trampling effects). Reduction of light within the plots was recorded over 9 weeks. Percentage cover of seagrasses and macroalgae and shoot density of seagrasses were measured over 12 weeks to assess the impact of shading and trampling by seaweed farming activities. Light was significantly reduced in the seaweed farm plots by 75 to 90% by the end of a seaweed growth cycle. H. stipulacea, despite its capacity for rapid growth, was significantly affected by the combination of shading and trampling under the seaweed farm treatment, while the climax seagrass species T. hemprichii was unaffected. Due to the decline in H. stipulacea, benthic macroalgae cover increased in the seaweed farm treatment, suggesting a change in seagrass community dynamics. In contrast, trampling had a negative effect on the benthic macroalgae as an isolated disturbance, which suggests that seagrasses are more resistant to trampling than macroalgae and would likely dominate the benthic macrophyte community under these conditions.

A Current Supported PV Array Reconfiguration Technique to Mitigate Partial Shading

Partial shading in a solar PV plant is an important concern as it reduces the output power. Dynamic array reconfiguration (DAR) helps in reducing the impact of partial shading. But, it has its own limitations. Further, DAR does not guarantee single peak in array power-voltage characteristics during partial shading. It requires sophisticated and costly MPPT controller to track the global peak in order to extract maximum power from the PV array. In this paper, an improved DAR strategy is proposed using current injection (CI). This CI-based DAR strategy enhances the array power output beyond what is achievable by the available DAR techniques. Using this technique, multiple peaks in the power-voltage characteristics of the PV array are also avoided. The proposed method is evaluated for different levels of shading and its patterns. Experimental results establish the superiority of the CI-based DAR method over the available PV array reconfiguration strategies.

Impact of Uneven Shading by Neighboring Buildings and Clouds on the Conventional and Hybrid Configurations of Roof-Top PV Arrays

Partial shading is the commonly encountered scenario of building roof-top based PV arrays that mainly occur due to the shadow of the neighbouring buildings and clouds resulting in unexpected losses and deteriorated system performance. The arrays are connected in various configurations to enhance the system performance during shading. In this paper, various conventional and hybrid interconnection configurations based on series-parallel (SP), bridge-linked (BL), and total cross tied (TCT) topologies of the roof-top PV arrays are examined under various partial shading scenarios caused by the neighbouring building and clouds. The investigation is done for a $9\times 9$ roof-top array in MATLAB/Simulink environment considering various comparison parameters. It has been found that during 1.23%, 7.40%, 11.11%, 17.75%, 18.51%%, 22.22%, and 24.69% of total array shading, SP generated the maximum power whereas, during 30.86%, 61.72% shading, TCT has the generated only a slightly higher power as compared to SP. Hence, the study concludes that the configurations have a puny effect on the power generation of the arrays during uneven shading patterns caused by buildings and clouds.

Mortality benefit of building adaptations to protect care home residents against heat risks in the context of uncertainty over loss of life expectancy from heat

We explore methodological issues core to the cost-benefit evaluation of building adaptations designed to protect against heat risks to residents of care homes in England in the context of the uncertainties relating to the loss of life expectancy in heat death. We used building physics modelling to quantify the impact of external window shading on indoor temperatures. We calculated associated heat mortality and loss of life expectancy under three sets of assumptions of life-shortening based on: (Method 1) an England & Wales (E&W) life-table, (Method 2) E&W life-table scaled to match observed average survival of care home residents and (Method 3) assuming that those dying of heat have a life expectancy of six months. External window shading was estimated to reduce mean indoor temperatures by 0.9 °C in a ‘warm’ summer and 0.6 °C in an ‘average’ summer. In a care home of 50 residents, the heat deaths and years of life lost (YLL) averted by such shading were estimated by the three life-expectancy assumptions (Methods 1, 2, 3) to be: 0.07, 0.47 and 0.28 heat deaths and 0.29, 0.76 and 0.14 YLL for the warm year and 0.05, 0.31 and 0.19 heat deaths and 0.20, 0.51 and 0.10 YLL for the average year. Over a 20-year time horizon and assuming an annual discount rate of 3.5%, the monetized benefit of reduced YLL would be around £90,000, £230,000 and £44,000 with the three life-expectancy assumptions. Although this range represents appreciable uncertainty, it appears that modest cost adaptations to heat risk may be justified in conventional cost-benefit terms even under conservative assumptions about life expectancy.

A simple and robust shade correction scheme for remote sensing reflectance obtained by the skylight-blocked approach

The skylight-blocked approach (SBA) provides a direct and high-precision measurement of the water-leaving radiance (Lw), which allows a confident determination of the remote sensing reflectance (Rrs), where Rrs is defined as the ratio of Lw to the downwelling irradiance just above the surface. However, the Rrs obtained by SBA is subject to self-shading error. The present shade error correction scheme (Shang17, [Appl. Opt. 56, 7033-7040, 2017]), implemented via spectral optimization, encounters large errors if there is a mismatch in the spectral models of the component inherent optical properties (IOPs). Following the concept of the quasi-analytical algorithm (QAA, [Appl. Opt. 41, 5755-5772, 2002]), a novel scheme (ShadeCorrQAA) is proposed without the need to model the component IOPs. Evaluations with numerical simulations and controlled measurements show that ShadeCorrQAA outperforms Shang17 in all water types and can correct the shade impact excellently, even for highly productive waters. ShadeCorrQAA is further improved at the chlorophyll fluorescence band, where a constructed absorption coefficient is used to estimate the shade error. Collectively, ShadeCorrQAA, with higher accuracy and broader applicability than Shang17, is recommended for the shade correction associated with SBA and other similar measurements where there is a shade impact on Rrs.

Techno-Economic Assessment of Rooftop PV Systems in Residential Buildings in Hot–Humid Climates

The application of renewable energy has been an integral part of the sustainability drive in the building sector and solar photovoltaic (PV) is one of the most effective technologies in this respect. The present study aims to investigate the prospects of solar PV in residential buildings in the hot–humid climatic conditions. The study discusses the utilization of building roofs for the application of PV in terms of potential hurdles and utilization factor (UF). Technical performance of PV systems has also been investigated in terms of power output as well as the energy saved as a result of the shading impact of panels for two types of residential units, apartments and villas. Investigation of 70 sample residential buildings reveals the average UF of 0.21 and 0.28 for apartments and villas, respectively. For the case study of apartment and villa residential units, roof UF has been found to be 13% and 15% with a respective PV output of 6079 kWh/year and 6162 kWh/year. Potential PV output at the city level has also been estimated. A sensitivity analysis has been conducted to evaluate the impact of various cost and design parameters on the viability of PV systems.

Prediction of the Impact of Tower Shading on Resource Parameters and Performance by Using LiDAR

Prediction of the Impact of Tower Shading on Resource Parameters and Performance by Using LiDAR

158 Provision of artificial shade before weaning influences performance of Angus and Brangus cow-calf pairs

Abstract A completely randomized design study with a 2 × 2 factorial arrangement of treatments evaluated the impact of artificial shade (SHADE or NO SHADE) and breed (ANGUS vs. BRANGUS) on performance of cows, nursing calves, and subsequent offspring. Twenty-four Angus and 24 Brangus black-hided pregnant cows (579 ± 8 kg BW; 6.5 yr; approximately 85 d of gestation) and their nursing calves were randomly allocated to 12 ‘Pensacola’ bahiagrass pastures (Paspalum notatum Flüggé; 1.3 ha; n = 4 pairs/pasture), with or without access to artificial shade (NO SHADE BRANGUS [NSB], NO SHADE ANGUS [NSA], SHADE BRANGUS [SB], and SHADE ANGUS [SA]) for 56 d during summer. Body condition score (BCS) of cows and BW of pairs were obtained on d -1, 0, 55, and 56 (weaning weight). Following weaning, calves were randomly allocated to 4 pens (n = 12/pen) equipped with GrowSafe feed bunks for 14 d to measure feed intake (DMI) and efficiency (G:F). A shade × breed interaction (P < 0.05) was observed for average daily gain (ADG) and BCS of cows, with SB being greatest (P ≤ 0.05). Pre-weaning calf ADG tended to be greater (P = 0.10) for SHADE vs. NO SHADE. Weaning weight and BW 14-d post-weaning were lesser for NSB vs. NSA, SA, and SB, whereas no differences in DMI, ADG, or G:F were observed (P > 0.11). Gestation length was greater for SHADE vs. NO SHADE cows (292 vs. 274; P = 0.02), but calf birth weight was not different. Providing artificial shade to pregnant-lactating beef cows positively impacted the growth of Brangus but not Angus cows. However, weaning BW of calves from Angus cows regardless of shade access did not differ from that of Brangus calves with shade. Further research should investigate the potential long-term effects of shade on the subsequent offspring.

114 Monitoring the impact of shade and housing on physiological response in finishing beef cattle during the summer months in the Southeastern United States

Abstract A study was conducted to evaluate the effect of heat stress on blood-gas parameters of beef steers finished with or without shade in the Southeastern United States. Thirty-two steers (BW 453kg +/-4 kg) were assigned to one of four treatment groups including: inside with fans (CWF), inside no fans (CNF), outside with shade (SHADE), and outside without shade (OUT). All animals were placed into their treatment on d-10 and were given 10 days to acclimate. Animals were fed individually and served as the experimental unit. Animals were weighed and arterial blood was collected on d-10, 0, and 50. Data were analyzed in a completely randomized designed utilizing a one-way ANOVA. Initial (d-10) pCO2 values were similar for all treatments (P >0.05). On d0, covered treatments (SHADE, CWF, and CNF) pCO2 values were greater than d-10 (P< 0.01), OUT values did not differ from d-10 to d0 (P = 0.95). The change in pCO2 values between d-10 to d0 values were similar for covered groups (P >0.14) and greater than OUT (P < 0.02). On d50 all treatment pCO2 values returned to baseline values (P = 0.50), and the change in pCO2 from d0 to d50 was greater for covered groups than the OUT group (P < 0.04) Initial d-10 pO2 values were similar for all treatments (P >0.05). On d0, covered treatments (SHADE, CWF, and CNF) pO2 values were less than d-10 (P < 0.01), OUT values did not differ from d-10 to d0 (P = 0.75). pCO2 values between d-10 to d0 were similar across all groups (P = 0.38). On d50 SHADE and CNF pO2 values were less than base line (P < 0.02). d50 pO2 values for OUT and CWF returned to baseline values (P >0.20). The change in O2 from d0 to d50 was similar across all groups (P = 0.84). These results suggest that there is a physiological difference between beef steers fed with cover versus beef steers outside.

Impact of heavy rainfall events and shading on the temperature of sea turtle nests

While most studies assessing the ecological impacts of climate change have examined impacts from warming temperatures, less attention has been given to other parameters such as increased rainfall events. At a nesting rookery in the northern Great Barrier Reef, Australia, we used data loggers to examine the impact of heavy rainfall and shade on the nest temperatures for green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles clutches, which have temperature-dependent sex determination. In the middle of the nesting season (December–March), on 21 January 2019, 125 mm of rain fell over two days, causing the temperature to initially decrease by an average of ~ 3.6 °C in hawksbill turtle nests (n = 18) and ~ 3.5 °C in green turtle nests (n = 9). For shaded clutches during the 20-day cooling period after the rainfall event, we report average nest temperatures of ~ 27.9 °C and ~ 28.2 °C for hawksbill and green turtle clutches respectively, falling well into the male-producing range for sex determination. This was profoundly cooler than the average nest temperatures of clutches without shade and prior to the heavy rainfall, which was ~ 31.3 °C for both species. Extreme rainfall events are predicted to increase around Australia due to climate change but may help counteract impacts of atmospheric warming on sea turtle offspring sex-ratios. Our results also show the potential for artificially cooling nests by applying a combination of shade and irrigation, to counter the expected increases in the feminisation of sea turtle hatchling production worldwide.

Impacts of shade on cattle well-being in the beef supply chain.

Shade is a mechanism to reduce heat load providing cattle with an environment supportive of their welfare needs. Although heat stress has been extensively reviewed, researched, and addressed in dairy production systems, it has not been investigated in the same manner in the beef cattle supply chain. Like all animals, beef cattle are susceptible to heat stress if they are unable to dissipate heat during times of elevated ambient temperatures. There are many factors that impact heat stress susceptibility in beef cattle throughout the different supply chain sectors, many of which relate to the production system, that is, availability of shade, microclimate of environment, and nutrition management. The results from studies evaluating the effects of shade on production and welfare are difficult to compare due to variation in structural design, construction materials used, height, shape, and area of shade provided. Additionally, depending on operation location, shade may or may not be beneficial during all times of the year, which can influence the decision to make shade a permanent part of management systems. Shade has been shown to lessen the physiologic response of cattle to heat stress. Shaded cattle exhibit lower respiration rates, body temperatures, and panting scores compared with unshaded cattle in weather that increases the risk of heat stress. Results from studies investigating the provision of shade indicate that cattle seek shade in hot weather. The impact of shade on behavioral patterns is inconsistent in the current body of research, with some studies indicating that shade provision impacts behavior and other studies reporting no difference between shaded and unshaded groups. Analysis of performance and carcass characteristics across feedlot studies demonstrated that shaded cattle had increased ADG, improved feed efficiency, HCW, and dressing percentage when compared with cattle without shade. Despite the documented benefits of shade, current industry statistics, although severely limited in scope, indicate low shade implementation rates in feedlots and data in other supply chain sectors do not exist. Industry guidelines and third-party on-farm certification programs articulate the critical need for protection from extreme weather but are not consistent in providing specific recommendations and requirements. Future efforts should include: updated economic analyses of cost vs. benefit of shade implementation, exploration of producer perspectives and needs relative to shade, consideration of shade impacts in the cow–calf and slaughter plant segments of the supply chain, and integration of indicators of affective (mental) state and preference in research studies to enhance the holistic assessment of cattle welfare.

Shade trees preserve avian insectivore biodiversity on coffee farms in a warming climate.

AimCoffee is an important export for many developing countries, with a global annual trade value of $100 billion, but it is threatened by a warming climate. Shade trees may mitigate the effects of climate change through temperature regulation that can aid in coffee growth, slow pest reproduction, and sustain avian insectivore diversity. The impact of shade on bird diversity and microclimate on coffee farms has been studied extensively in the Neotropics, but there is a dearth of research in the Paleotropics.LocationEast Africa.MethodsWe created current and future regional Maxent models for avian insectivores in East Africa using Worldclim temperature data and observations from the Global Biodiversity Information Database. We then adjusted current and future bioclimatic layers based on mean differences in temperature between shade and sun coffee farms and projected the models using these adjusted layers to predict the impact of shade tree removal on climatic suitability for avian insectivores.ResultsExisting Worldclim temperature layers more closely matched temperatures under shade trees than temperatures in the open. Removal of shade trees, through warmer temperatures alone, would result in reduction of avian insectivore species by over 25%, a loss equivalent to 50 years of climate change under the most optimistic emissions scenario. Under the most extreme climate scenario and removal of shade trees, insectivore richness is projected to decline from a mean of 38 to fewer than 8 avian insectivore species.Main conclusionsWe found that shade trees on coffee farms already provide important cooler microclimates for avian insectivores. Future temperatures will become a regionally limiting factor for bird distribution in East Africa, which could negatively impact control of coffee pests, but the effect of climate change can be potentially mediated through planting and maintaining shade trees on coffee farms.

Effects of shade trees on robusta coffee growth, yield and quality. A meta-analysis

Productivity of coffee plantations is threatened by both climate change and decreasing revenues of coffee growers. Using shade trees might protect against temperature variability, erosion and excessive radiation but there may be trade-offs in productivity and quality. While impacts of shade trees on arabica (Coffea arabica) have been reviewed, a global synthesis on robusta (Coffea canephora) coffee is lacking. We assessed how shade affects robusta growth and productivity, and what are the interactions and trade-offs. We conducted a systematic literature search in Web of Science and CAB s on 16 December 2019. Thirty papers fulfilled our inclusion criteria of being experimental studies on the impact of overstory trees with approximately half being from Brazil or India. Shade improved robusta tree growth and yield with some contrasting effects on physicochemical and biochemical properties. Shade (> 30%) was associated with reduced beverage quality. Significant interactions between shade and location, rainfall level and robusta clone were found. Among the clones tested, 06V, C153, LB1, GG229 and JM2 showed a higher productivity and growth (from + 17 to + 280%) under moderate shade (41–65%). This is the first meta-analysis of the effects of shade on robusta coffee. By synthesizing data from different studies, we highlight for the first time that the effect of shade on robusta coffee depends on tree age. Shade had positive impacts on older robusta trees (mean of 16 years), while the impact of shade on younger trees was either insignificant or negative. We highlight the importance of both clone type and tree ages. Research gaps included a lack of knowledge on the effects of shade with respect to coffee and shade tree age as well as interactive effects. More in-depth studies are needed to understand the mechanisms of how shade trees affect robusta coffee.

Impacts of shading on seedling growth and mineral accumulation in Paeonia lactiflora

Shading is one of the important strategies to protect seedlings of Paeonia lactiflora. The effects of shading treatments on seedling growth and mineral accumulation of Duolun P. lactiflora were investigated in a greenhouse experiment to provide guidance for P. lactiflora cultivation. One week after emergence, seedlings were treated with 20%, 40%, 60% or 80% shading for two months, with no-shading as the control (CK). The results showed that shading treatments significantly increased plant height by 19.9%, 31.1%, 52.9%, and 63.7%, respectively. However, shading significantly reduced the root mass ratio and root to shoot ratio by 21.5%, 23.6%, 29.2%, 41.8% and 40.6%, 44.0%, 50.9%, 63.2%, respectively. Moreover, 40%, 60% and 80% shading significantly increased specific leaf area by 77.0%, 84.1% and 65.2%, and significantly increased chlorophyll content by 92.3%, 128.7%, 98.1%, and increased carotenoid content by 86.9%, 113.1% and 90.5%, respectively. The treatments of 40%, 60%, and 80% shading significantly decreased root biomass by 61.4%, 74.3% and 78.6%, respectively. Compared with CK, 20%, 40% and 80% shading, the 60% shading treatment increased root phosphorus content by 245.7%, 65.9%, 40.5% and 10.3%, increased potassium content by 102.9%, 131.7%, 57.0%, 63.3% and magnesium content by 131.3%, 55.1%, 40.4%, 7.7%, respectively. 60% shading was an appropriate shading intensity for P. lactiflora seedling cultivation based on local conditions in Duolun.

Impact of roof shading on building energy performance in warm & humid climatic places of India

With the rise in awareness of energy efficient buildings and adoption of mandatory energy conservation codes across the globe, significant change is being observed in the way the buildings are designed. With the launch of Energy Conservation Building Code (ECBC) in India, climate responsive designs and passive cooling techniques are being explored increasingly in building designs. Of all the building envelope components, roof surface has been identified as the most significant with respect to the heat gain due to the incident solar radiation on buildings, especially in tropical climatic conditions. Since ECBC specifies stringent U-Values for roof assembly, use of insulating materials is becoming popular. Along with insulation, the shading of the roof is also observed to be an important strategy for improving thermal performance of the building, especially in Warm and humid climatic conditions. This study intends to assess the impact of roof shading on building’s energy performance in comparison to that of exposed roof with insulation. A typical office building with specific geometry and schedules has been identified as base case model for this study. This building is simulated using energy modelling software ‘Design Builder’ with base case parameters as prescribed in ECBC. Further, the same building has been simulated parametrically adjusting the amount of roof insulation and roof shading simultaneously. The overall energy consumption and the envelope performance of the top floor are extracted for analysis. The results indicate that the roof shading is an effective passive cooling strategy for both naturally ventilated and air conditioned buildings in Warm and humid climates of India. It is also observed that a fully shaded roof outperforms the insulated roof as per ECBC prescription. Provision of shading over roof reduces the annual energy consumption of building in case of both insulated and uninsulated roofs. However, the impact is higher for uninsulated roofs (U-Value of 3.933 W/m2K), being 4.18% as compared to 0.59% for insulated roofs (U-Value of 0.33 W/m2K).While the general assumption is that roof insulation helps in reducing the energy consumption in tropical buildings, it is observed to be the other way when insulation is provided with roof shading. It is due to restricted heat loss during night.

Mirid feeding preference as influenced by light and temperature‐mediated changes in plant nutrient concentration in cocoa

AbstractCocoa mirids are the most important insect pests of cocoa in West Africa. This study investigated the effect of environmental parameters that are modulated by overhead shade, that is, light intensity and temperature, on nutrient and phenolic concentrations in cocoa and their subsequent effect on mirid feeding. Eight‐month‐old cocoa seedlings were maintained for 50 days in two growth chambers set to day temperatures of 25 or 30°C. Each chamber had sections with different light intensities (541, 365 and 181 μmol m−2 s−1 photosynthetically active radiation [PAR]). For the field studies at Akim Tafo in Ghana, 8‐month‐old plants of three cocoa clones were subjected to shaded (PAR = 180 μmol m−2 s−1, between 11:00 a.m. and 12:00 p.m.) and unshaded (PAR = 1,767 μmol m−2 s−1, between 11:00 a.m. and 12:00 p.m.) treatments for 50 days after which nutrient measurements and mirid choice tests were carried out. No significant effect of environment was observed on the phenolic concentration of stems under controlled environment chamber conditions. However, in the field, the phenolic concentration of stems was significantly greater for unshaded compared with shaded plants (p = .04). Under controlled conditions, the leaf nitrogen concentration increased slightly with light intensity (p = .003). The same trend was seen in stems but only at 30°C. In the field, the impact of overhead shade on nitrogen varied between cocoa clones. The concentration of carbohydrates in both leaves and stems in the field was higher under unshaded conditions. When subjected to feeding tests, stems from unshaded cocoa had significantly more mirid feeding lesions (p = .003) after 24 hr exposure to mirids compared to shaded cocoa. Mirid feeding therefore appears not to be deterred by the higher phenolic levels but rather there was a preference for cocoa tissue grown under unshaded conditions. These findings highlight the need to consider the growing environment of cocoa clones when screening for varieties with resistance to mirids.

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