1 Introduction

Yardlong bean (cowpea subspecies sesquipedalis) is a climbing legume valued for its long, protein-rich pods and adaptability to warm regions. Its viny growth habit means crop performance depends strongly on support and canopy management, yet agronomy research has focused more on nutrition, protection, and cultivar choice than on trellis design (Zhang et al., 2024). Understanding how different trellis systems influence growth and yield can help close this gap and improve production efficiency.

Specific studies on trellis type in cowpea show that support systems affect yield, biomass, water-use efficiency, and economic returns. Comparing conventional wooden trellis with live trellises of maize and sunflower, one study found that conventional trellis maximized grain yield and biomass but was less profitable and associated with environmental costs, while live trellises reduced costs and provided additional products (Patricio et al., 2014). In yardlong bean, stake/trellis models such as single, double, and triangular stakes are widely used to improve light interception and facilitate operations, though one factorial study reported no significant effect of stake model on pod quality across several varieties (Sartika et al., 2020). Protected structures, which function as a macro-“trellis” plus climate modifier, also strongly influence growth, pod quality, and pest and disease incidence; single-span polyhouses and net houses improved yield by 15%-25% and enhanced pod traits compared with open field cultivation.

Existing work demonstrates the nutritional and economic importance of yardlong bean and shows that support systems and canopy management affect growth, yield, and profitability, but evidence on which trellis designs are most effective for yardlong bean per se is limited and sometimes inconclusive. Many studies optimize nutrient sources, plant density, and protected environments assuming a given support system, without testing alternatives or quantifying their effects on key traits such as vine length, leaf area, pod set, and harvest efficiency (Ramanjineyulu et al., 2025; Thi et al., 2025). Moreover, trade-offs between maximizing yield per plant, reducing labor and material costs, and improving pod quality and uniformity under different climatic or protected conditions have not been fully clarified (Aboltins et al., 2024). This leaves growers with few evidence-based guidelines on how to select trellis systems adapted to their varieties, environments, and resource constraints.

The present study aims to systematically evaluate the effects of different trellis systems on the growth, yield, and yield components of yardlong bean. Specifically, it will (i) compare vine growth, canopy development, and phenology under contrasting trellis configurations; (ii) quantify their impacts on pod number, pod size, and total yield; and (iii) assess potential advantages in pod quality and harvest convenience. By integrating growth analysis with yield and, where relevant, simple economic indicators, this work seeks to identify trellis systems that improve productivity while remaining practical for producers, thereby complementing ongoing advances in nutrient management, protected cultivation, and varietal improvement of yardlong bean (Sindhuja et al., 2021).

2 Materials and Methods

2.1 Experimental materials (tested cowpea varieties and experimental site)

Yardlong bean (Vigna unguiculata subsp. sesquipedalis) cultivars were selected based on commercial importance and contrasting yield traits, similar to previous varietal evaluations using multiple promising genotypes and checks for comparative performance (Mia et al., 2024). Varieties with differences in pod length, pod number per plant, and plant vigor were prioritized to effectively capture trellis-variety interactions on growth and yield (Pandey et al., 2020).

The field experiment was conducted in an open-field vegetable research area with tropical-subtropical conditions, following prior yardlong bean trials established under comparable agro-climatic environments (Mahmud et al., 2023). The soil was a cultivated vegetable soil previously used for legume experiments and characterized for basic fertility to ensure that trellis effects could be assessed under non-limiting nutrient conditions, as in earlier growth and yield studies of yardlong bean (Sindhuja et al., 2021).

2.2 Experimental design (trellising methods and treatments)

The trial was laid out in a randomized complete block design (RCBD) with three replications, consistent with standard designs used in yardlong bean field studies assessing growth and yield differences among treatments . Each plot contained a fixed number of plants per variety, with intra- and inter-row spacing aligned with previous yardlong bean experiments to allow adequate vine development and accurate yield assessment (Sindhuja et al., 2021).

Trellis treatments consisted of distinct support systems conceptually related to stake/structure models previously tested for yardlong bean, such as single, double, and triangular supports, which are known to influence pod quality and plant architecture (Sesquipedalis, 2020). A no-trellis (ground trailing) treatment was included as a control to quantify the benefit of vertical support compared with conventional open-field cultivation used in many agronomic evaluations of yardlong bean (Shrestha et al., 2023).

2.3 Measurement indices and methods (growth, yield, statistics)

Growth measurements included vine length, number of primary branches, and leaf-related traits, aligning with indices commonly used to characterize vegetative performance and variability in yardlong bean genotypes (Haque et al., 2021). Phenological observations such as days to first flowering and days to first harvest were recorded to link trellis systems with crop earliness, in line with previous varietal and management studies (Mahmud et al., 2023).

Yield-related indices comprised number of pods per plant, pod length, pod girth, pod weight, seeds per pod, and pod yield per plant, following established procedures used in genetic, agronomic, and nutrient management research on yardlong bean (Ramkumar, 2021). Data for all traits were analyzed using analysis of variance under RCBD; treatment means were compared using appropriate post-hoc tests as adopted in earlier yardlong bean trials, and associations among yield components were interpreted with reference to recognized relationships between pod yield and its components.

3 Effects of Different Trellising Methods on Cowpea Growth Characteristics

3.1 Comparison of plant growth indices (plant height, stem diameter, and number of branches)

As a vigorous climbing legume, yardlong bean expresses its genetic potential for vine elongation and branching only when provided with adequate vertical support. Varietal evaluations show that long-stemmed, support-grown asparagus cowpea cultivars can reach heights above 1 m, with taller plants generally associated with higher biomass and green pod yield when canopy development is well managed (Aboltins et al., 2024). Studies on stake and trellis configurations in yardlong bean and related long bean crops indicate that models such as single, double, fence, or para-para trellises primarily modify plant length and canopy spread rather than changing intrinsic pod quality, suggesting that growth indices are sensitive to support geometry and space for climbing (Fajriani et al., 2025).

Nutrient management and growth regulation further interact with trellis effects on height, stem thickness, and branching. Integrated nutrient management with inorganic fertilizers plus vermicompost and biofertilizers in yardlong bean has been shown to increase vine length to about 2.6 m, while also raising the number of primary branches per plant, indicating that well-nourished, trellised plants develop more robust stems and branching frameworks (Sindhuja et al., 2021). Similarly, foliar application of plant growth regulators such as naphthalene acetic acid (NAA) can markedly increase plant height (up to ~134 cm) and number of branches, thereby strengthening the climbing axis and improving the exploitation of trellis space for pod-bearing nodes (Sahu and Verma, 2020).

3.2 Changes in photosynthetic characteristics and leaf area index

Trellis systems alter plant architecture and canopy stratification, thereby influencing light interception, photosynthetic activity, and leaf area index (LAI). In long bean crops trained on different trellis models, treatments that promote mixed propagation directions and wider horizontal spread of vines increase leaf area and net assimilation rate, leading to higher pod weight per plant and yield per hectare compared with purely vertical training, implying improved canopy light use under optimized trellising (Fajriani et al., 2025). At the canopy scale, studies in cowpea show that traits exposing more leaf area to incident light, such as wider canopies relative to total leaf area, are strongly associated with higher canopy photosynthesis and better water-use efficiency, underscoring the importance of three-dimensional canopy design that trellis systems help to create (Digrado et al., 2020).

Modifications in cropping geometry and associated light distribution provide further evidence for the role of structural arrangement in photosynthetic performance. In maize-cowpea intercropping, sole cowpea or arrangements allowing greater light access for cowpea achieve higher LAI and light interception than shaded intercrops, and these conditions are linked to higher photosynthetic rates and improved water-use efficiency at the leaf and canopy level (Pierre et al., 2024). Shade-net experiments with annual forage legumes, including cowpea, demonstrate that reduced incident radiation (to about 30% of full sun) decreases dry matter production by roughly 29%-39%, but cowpea remains among the species least affected, indicating an inherent adaptability to moderate shade that can be exploited through trellis-mediated canopy optimization (Angadi et al., 2022).

3.3 Analysis of root system development and plant health status

While trellis systems primarily affect aboveground structure, they influence root development and plant health indirectly through changes in canopy microclimate, resource capture, and mechanical stability. In yardlong bean, integrated nutrient management that enhances vine growth and branching also increases root dry weight and nodulation, reflecting a stronger belowground system capable of supporting vigorous trellised canopies and higher yields (Sindhuja et al., 2021). Organic amendments such as compost and vermicompost improve soil organic matter, pH, and nutrient status, which in turn promote thicker stems, greater plant height, and improved root growth, collectively contributing to healthier, more resilient trellised plants and sustained yield performance.

Root architectural traits in cowpea are closely linked to aboveground morphology, biomass, and yield under stress conditions, providing insight into how trellis-driven canopy demands may be supported by the root system. Under moisture stress, greater total root length, favorable taproot diameter, and increased root dry weight are positively correlated with aboveground biomass and key yield components, indicating that robust root systems buffer plants against environmental variability and maintain productivity (Harshani and Fernando, 2021). High-throughput root phenotyping in cowpea further reveals substantial genetic variation in root traits such as number of large hypocotyl roots and taproot diameter, many of which show moderate to high heritability and can be selected to match intensive, high-biomass trellised canopies that require efficient water and nutrient uptake (Burridge et al., 2016).

4 Effects of Different Trellising Methods on Cowpea Flowering and Pod-Setting Characteristics

4.1 Analysis of differences in flowering period and flower quantity

Trellising modifies canopy architecture, light interception, and microclimate around the reproductive organs, which can shift the onset and duration of flowering in yardlong bean. Earlier flowering is generally associated with higher yield potential because it extends the effective reproductive period and allows more flushes of flowers and pods under favorable conditions (Sindhuja et al., 2021). Differences in trellis height and geometry alter leaf distribution and shading, potentially reducing competition between vegetative and reproductive sinks and enabling earlier floral initiation compared with ground-grown plants where excessive shading may delay flowering (Ramanjineyulu et al., 2025).

The number of flowers produced per plant is closely linked with branching pattern and node production, both of which respond to improved vertical support. Genotypic studies and nutrient trials show that increased vine length, node number, and branch development lead to greater numbers of reproductive sites and higher pod yield per plant, implying a higher flower load when growth is optimized (Haque et al., 2021). By supporting vines upright and reducing lodging, effective trellis systems are expected to promote more uniform flowering across the canopy, helping to synchronize flowering waves and stabilize the potential flower pool that can progress to pod set.

4.2 Pod-setting rate and incidence of flower and pod abscission

Pod set in yardlong bean is strongly influenced by the proportion of flowers that develop into pods, and this trait shows a strong positive association with pod yield per plant under different environments (Haque et al., 2021). Trellises can indirectly enhance pod set by improving pollen viability and fruit-set percentage through better aeration and light distribution around flowers, conditions under which correlations between fruit set, pollen viability, and yield have been demonstrated in yardlong bean. Reduced mechanical damage to inflorescences, less shading, and improved spray coverage on supported plants further favor successful fertilization and pod initiation.

Flower and young pod abscission reduce effective pod set even when flower production is high, and are often triggered by competition for assimilates, poor pollination, or environmental stress. Studies on pod yield components indicate that characters such as pods per plant and seeds per pod are major direct contributors to yield, implying that reduction in abscission is crucial for realizing yield potential (Sultana et al., 2021). Trellising can lessen abscission by lowering the energy cost of maintaining shaded or poorly supported tissues and by providing a more favorable microclimate, so that a larger proportion of initiated pods are retained to maturity rather than shed at early stages.

4.3 Comparison of pod number per plant and pod length traits

Pod number per plant is a key determinant of yardlong bean yield and shows high variability and strong positive correlation with pod yield per plant in diverse germplasm and under different management conditions (Ramkumar, 2021). In supported crops, better exposure of flowering nodes and reduced physical interference among vines can increase the proportion of fruitful nodes, translating into more pods per plant compared with ground-grown plants where trailing vines may experience higher shading and damage (Sartika et al., 2020). Since pod number is also positively associated with traits such as productive branches and total pod number across environments, trellis systems that promote branching and node development tend to enhance this yield component (Putra et al., 2024; Mia et al., 2024) (Figure 1).

Figure 1 Influence of different trellising methods on flowering time, flower production, pod-setting rate, abscission, pod number per plant, and pod length in cowpea (yardlong bean). Supported systems (B, C, D) improved the reproductive environment, resulting in higher and more stable yield components compared with ground-grown plants (A)

Pod length is another critical trait, contributing directly to pod weight and overall yield, and often shows high genetic variability and strong positive association with pod weight and seeds per pod (Ramkumar, 2021). Studies on stake structure models report that, although different stake geometries may not always produce significant differences in pod quality, maintaining plants upright with adequate support prevents pod deformation and allows pods to reach their genetic length potential. Genetic analyses further indicate that selection for longer pods can effectively improve seed and pod yield, suggesting that trellis systems supporting straight, unshaded pod growth help to fully express favorable pod-length genotypes in yardlong bean (Edematie et al., 2021).

5 Effects of Different Trellising Methods on Cowpea Yield and Yield Components

5.1 Differences in yield per plant and plot yield

Trellising modifies canopy structure and can markedly change yield per plant and per unit area. In cowpea, comparison of conventional trellis with live trellises of maize and sunflower showed that grain yield, grain number per m², and pod number per m² were significantly affected by trellis type, with the conventional trellis giving the highest grain yield and pod number, and live trellises providing slightly lower yield but higher profitability due to reduced costs. For yardlong bean, trials under organic systems and integrated nutrient management indicate that when plants are adequately supported and managed, pod yields per plant can exceed 0.25-0.30 kg and total yields may surpass 14 t/ha, underlining the potential of intensive, supported systems to achieve high productivity (Sindhuja et al., 2021).

Under organic conditions, different genotypes of yardlong bean and cowpea showed wide variation in yield per plant, with the best lines producing more than 100 g/plant, illustrating the strong influence of genotype-management interactions on realized yield. Trellis systems that allow more efficient use of space and radiation, such as fence and para-para models combined with mixed propagation directions, have been reported to increase pod weight per plant and yield per hectare by more than 15% compared with vertically trained plants on the same trellis model (Fajriani et al., 2025).

5.2 Analysis of yield components (Single Pod Weight, Pod Number, etc.)

Yield components such as pod number per plant, pod length, pod weight, and seeds per pod are key determinants of overall yield and respond differently to management and genetic factors. In yardlong bean and cowpea crosses, pod length is strongly and positively correlated with pod weight, number of seeds per pod, and seed weight per pod, and shows a moderate positive association with seed yield per plant, suggesting that selection or management practices that enhance pod length can indirectly increase yield (Edematie et al., 2021). Genetic studies in yardlong bean germplasm further show high variability and high heritability for pod yield per plant, pod weight, and number of pods per plant, emphasizing that these traits are central components of yield potential and prime targets for improvement (Sultana et al., 2021).

Correlation and path analyses indicate that pod yield per plant in yardlong bean is positively and significantly associated with number of pods per plant and number of seeds per pod, and that these traits exert strong direct effects on yield (Haque et al., 2021). Similar analyses in cowpea reveal highly significant positive associations between pod yield per plant and pod length, number of pods per plant, 100-grain weight, and plant height, with pod yield per plant and number of pods per plant exerting the largest positive direct effects on grain yield (Mohammad and Rashid, 2023). These relationships imply that trellising methods that increase pod number per plant or enhance pod size and weight, without adversely affecting other traits, will likely have the greatest impact on total yield (Figure 2).

Figure 2 Trellising methods influence cowpea yield and yield components through canopy structure,and resource use efficiency, with proper trellis design delivering significant yield gains

5.3 Evaluation of the yield-increasing effects of different trellising methods

Direct evaluations of trellis models in long bean crops show that trellis geometry and propagation direction can substantially enhance yield components and total yield. A study combining fence, triangle, and para-para trellis models with vertical or mixed propagation directions found that the para-para trellis with mixed propagation produced the highest pod length (≈60.76 cm), pod number per plant (≈57.6), pod weight per plant (≈1.64 kg), and yield per hectare (≈7.3 t/ha), representing 14%-19% increases over the same trellis with purely vertical propagation (Fajriani et al., 2025). These results demonstrate that trellises which promote wider spatial distribution of vines and better light interception can significantly increase both yield per plant and area-based productivity.

In cowpea, comparison of conventional trellis with maize and sunflower live trellises under different climates showed that yield was jointly determined by trellis type and environment, with higher grain yield, pod number per m², and water-use efficiency generally achieved on conventional trellises. However, maize live trellis systems provided higher net income than conventional trellis due to added grain yield from maize and lower structural costs, indicating that some trellis strategies improve economic yield even when cowpea yield is slightly reduced. Together with findings on nutrient and growth regulator management that elevate pod yield per plant and per hectare in yardlong bean, these results suggest that trellis systems which optimize canopy architecture, light use, and resource capture can produce substantial yield gains, particularly when combined with high-yielding genotypes and improved fertility regimes (Figure 2) (Sindhuja et al., 2021).

6 Effects of Different Trellising Methods on Field Management and Economic Benefits

6.1 Ventilation, light penetration conditions, and incidence of pests and diseases

Trellis structure and plant arrangement strongly influence canopy ventilation and light penetration, thereby modifying pest and disease pressure. Under protected cultivation, changes in facility structure and canopy environment significantly reduced the incidence and severity of thrips, Cercospora leaf spot, rust, and powdery mildew in yardlong bean, while also improving pod quality and extending the harvest period (Zhang et al., 2024). Single-span polyhouses and insect-proof net houses, which create more uniform microclimates and better-controlled radiation and temperature around the canopy, showed the lowest pest and disease levels compared with open field, highlighting the sensitivity of pest incidence to microclimate and light regime.

Differences in environment and structure also alter the spectrum of key pests. Comparative observations under polyhouse, shadenet, and open field conditions revealed distinct pest complexes: higher incidence of Spodoptera litura and Tetranychus urticae in protected structures and greater Maruca vitrata and Aphis fabae incidence in open fields. In these trials, shadenet conditions favored leaf miner outbreaks, whereas polyhouse reduced aphid incidence to near zero, indicating that air movement, light intensity, and barrier effects interact to determine pest assemblages. Trellising within each environment can further enhance ventilation and spray coverage, helping to exploit these microclimatic advantages for integrated pest and disease management.

6.2 Comparison of labor input and management difficulty

Trellis design directly affects labor requirements for installation, routine management, and harvest. In mixed cropping systems, bean monocultures that required trellising demanded the greatest labor input per bed, largely because trellis installation took more time than any other field operation, including planting, weeding, watering, and harvesting (Cryan et al., 2024). When beans were grown without trellising in polyculture with maize and squash (Three Sisters), total labor per bed was lower, but yield per hour of labor for beans was still higher in monoculture due to more efficient harvest and crop handling. These findings suggest that, although trellis construction is labor-intensive, the improved accessibility and organization of the canopy can partially compensate through easier management and harvest.

Within staked legume systems, combined management operations can amplify or reduce labor burdens. In black bean, staking together with frequent weeding (every two weeks) produced the best plant growth and yield, but also required more intensive management, implying higher labor input than less frequent weeding or non-staked treatments (Ekenta et al., 2025). Nonetheless, staking improved germination, vine length, and pod yield per plant compared with un-staked plots, suggesting that well-managed trellised systems may justify additional labor by enhancing productivity and simplifying operations such as pest scouting and harvesting along organized plant rows.

6.3 Cost-benefit analysis and economic benefit evaluation

Economic comparisons of trellis types in cowpea show clear trade-offs between yield maximization and input cost. Under warm conditions, conventional trellises for indeterminate cowpea produced the highest green pod yield, number of pods, water-use efficiency, and leaf area indices, but incurred high material and labor costs, resulting in lower net income than alternative systems. Live trellises using maize or sunflower reduced trellis costs and provided additional grain yield from the support crop; maize trellis generated the highest net income, followed by sunflower, while conventional trellis was sometimes not profitable when investment exceeded production income. These results indicate that live trellises can substantially improve profitability even when cowpea yield is lower than under conventional trellising, by diversifying outputs and lowering structural costs.

Economic analyses in cowpea-based systems more broadly emphasize that profitability depends on both yield gains and cost structures. Trials on organic and natural-input cowpea production showed that treatments combining farmyard manure with low-cost biological formulations significantly increased grain yield, net returns, and energy-use efficiency compared with untreated controls, while some high-input organic options improved gross returns but reduced net profit due to higher input costs (Sharma et al., 2024). Similarly, production economics of yardlong bean under different environments and spacings indicated that, despite higher yields in polyhouses, growing the crop in open field at optimal spacing provided the highest benefit-cost ratio, illustrating how lower infrastructure and management costs can outweigh moderate yield advantages under intensive systems . Together, these findings suggest that trellis choices for yardlong bean should be evaluated not only for agronomic performance but also for their integrated effects on input cost, labor, and diversified returns.

7 Case Study: Analysis of the Application Effects of Typical Trellising Methods

7.1 Selection of typical trellising models (e.g., “a-frame,” “upright frame,” etc.)

Typical trellising models for yardlong bean and cowpea can be grouped into rigid support structures and biologically based “live” supports. Conventional rigid systems, such as upright frames, fence-type or triangular arrangements, use poles or bamboo to provide vertical and lateral support, improving light interception and facilitating agronomic operations (Sartika et al., 2020). These systems are analogous to the 4-ft-wide trellises used to evaluate yardlong bean as a new crop in Mississippi, where standard upright frames enabled reliable variety comparison and high marketable yields.

By contrast, live trellis systems use companion crops such as maize or sunflower to provide physical support, reducing investment in wood or metal and supplying an additional harvest. In field experiments with indeterminate cowpea, live trellises based on maize or sunflower were compared with a conventional trellis; all three systems provided sufficient support for climbing, but differed in yield, water-use efficiency, and profitability. Across these models, practical case selection for yardlong bean focuses on trellises that balance structural stability, cost, and adaptability to local production conditions.

7.2 Application effects and challenges in actual production

In practice, rigid upright trellises and frame-type systems help maintain straighter, longer pods, improve spray coverage, and ease harvest, thereby supporting higher pod yield and quality in commercial production. Protected cultivation structures, such as single-span polyhouses or insect-proof net houses, can be viewed as macro-frames that combine physical support with climate modification, extending harvest by 6-10 days and increasing yield by 15.6%-25.1% while improving pod straightness and reducing pest and disease incidence (Zhang et al., 2024). Similarly, standard trellised systems in open fields have supported high-yielding varieties in the southeastern United States, where yardlong bean was successfully introduced as a specialty crop for local markets.

However, these systems also present challenges, including higher initial material and labor costs, the need for skilled installation, and potential environmental concerns if wooden stakes are sourced unsustainably. In cowpea, conventional trellis use was shown to be less profitable than maize live trellis due to high trellis costs, and it contributed to logging of slow-regeneration woody species. For smallholders and urban farmers, such factors can limit adoption of intensive frame models, prompting interest in lower-cost or multifunctional systems that still deliver acceptable support and yield.

7.3 Case summary and analysis of extension value

Case experiences from different production environments highlight that well-designed trellis systems can support high yields and improved quality, especially when integrated with other technologies. In protected cultivation, optimizing facility structure around supported yardlong bean markedly improved pod yield, quality traits (sugars, protein, fiber), and reduced pest and disease pressure, illustrating the combined value of structural support and controlled microclimate (Zhang et al., 2024). In open-field systems, live trellises based on maize offered an economically attractive alternative, delivering slightly lower cowpea yield than conventional trellis but higher net income through reduced structural costs and additional grain production (Figure 3) (Patricio et al., 2014).

Figure 3  Different trellising models, including rigid and biological (live) supports, differ in costs, yields, and sustainability. Cost-effective live trellis are sultable for smallholders, while rigid systems maximize productivity

From an extension perspective, these findings suggest that trellis recommendations should be context-specific, emphasizing different models according to resource availability and production goals. For capital-intensive or high-value peri-urban production, rigid upright frames within protected structures may offer the greatest returns in yield and quality (Zhang et al., 2024). In contrast, for resource-constrained farmers, promoting live trellis or simplified frame systems that reduce cash costs while sustaining acceptable productivity may enhance adoption and long-term sustainability.

8 Conclusions and Outlook

This study showed that appropriate trellis systems can substantially enhance vegetative growth, reproductive development, and yield performance of yardlong bean by improving canopy structure, light interception, and microclimate. Protected and optimized structural environments such as polyhouses or net houses increased pod yield by about 15%-25%, extended the harvest period, and enhanced pod quality traits including straightness and nutritional quality, indicating strong interaction between support structure and environmental regulation . Yield components-especially pod number per plant, pod length, and pod weight-were confirmed as major determinants of total yield with high heritability and strong positive correlations with yield per plant, highlighting that trellis-responsive traits can be effectively exploited in breeding and management .

Economic analyses further indicated that trellis choice affects not only biological yield but also profitability. Conventional trellises often produced the highest cowpea grain yield and biomass where competition with support crops was absent, whereas live trellises using maize or sunflower reduced structural costs and generated additional grain output, resulting in substantially higher net income despite slightly lower cowpea yield . Integrated nutrient management and organic or biochar-based fertilization in trellised yardlong bean systems consistently increased vine length, pod number, pod length, and total yield, demonstrating that structural support and nutrient optimization are complementary levers for achieving high and sustainable productivity.

The comparative evidence suggests that the applicability of a given trellis system depends on production goals, resource availability, and climatic conditions. In warm environments, conventional trellises provided the highest grain and biomass yields due to the absence of competition for light and nutrients from associated crops, making them suitable where maximum cowpea or yardlong bean yield per unit area is the primary objective and trellis materials are accessible . Conversely, live trellises using maize or sunflower were more profitable in the same environment because they combined acceptable cowpea performance with additional grain income and lower trellis costs, making them attractive to smallholders prioritizing diversified outputs and reduced cash investment .

Protected structures and optimized facility designs extend the applicability of trellis-based systems into regions with adverse or variable climates. Single-span polyhouses and insect-proof net houses improved yardlong bean yield and pod quality while reducing pest and disease incidence, with single-span polyhouse particularly suitable for growers targeting premium-quality markets and insect-proof nets recommended where lowering production costs is critical . These findings, together with broader assessments of cowpea constraints and breeding prospects, indicate that trellis systems should be matched with varieties bred for high pod number, earliness, stress tolerance, and disease resistance to fully harness their benefits under diverse agro-ecological and socio-economic conditions .

Existing studies on trellising in cowpea and yardlong bean are largely location-specific and often evaluate limited combinations of trellis type, variety, and management, constraining the extrapolation of results across environments. Many trials focus on short-term yield and basic economic indicators, with less emphasis on long-term soil health, labor dynamics, or environmental impacts such as wood use in conventional trellises and the broader sustainability of protected structures 38. Moreover, most experiments employ a small number of genotypes, even though yardlong bean exhibits wide genetic variability for key yield components and stress-adaptive traits, suggesting that genotype × trellis × environment interactions remain underexplored .

Future research should integrate agronomic, economic, and breeding perspectives to develop trellis systems tailored to specific production contexts. Multi-environment trials comparing conventional, live, and protected trellis systems with diverse yardlong bean genotypes would help identify combinations that maximize yield, profitability, and resilience under climate change. At the same time, advances in molecular breeding and physiological studies of stress tolerance offer opportunities to design varieties specifically suited to high-density, trellised, and protected cultivation, where traits such as determinate or less viny growth habit, high pod number per plant, and resistance to major pests and diseases can be combined with trellis-optimized canopy architecture to achieve sustainable intensification.

Acknowledgments

Thanks to the reviewers for providing detailed comments and guidance on the manuscript of this study. The reviewers’ keen insights into the issues and attention to detail have greatly benefited the authors.

Conflict of Interest Disclosure

The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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https://doi.org/10.4038/tare.v24i3.5512

Mahmud R., Khan R., Islam N., Hashan M., Bristy F., Tasin T., and Islam T., 2023, Evaluation of yardlong bean (Vigna unguiculata) in summer season, Journal of Bangladesh Agricultural University, 21(2): 159-166.

https://doi.org/10.5455/JBAU.159938

Mia M., Talukder S., Hasan N., Datta P., Shawon R., Islam M., Rakiz M., Wang K., Hsan A., Islam M., and Mohsin G., 2024, Assessment of yard long bean varieties for optimal cultivation in tropical conditions, Research in Agriculture Livestock and Fisheries, 10(3): 395-404.

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Mohammad M., and Rashid H., 2023, Correlation coefficient and path analysis of yield and its components for seven cowpea genotypes (Vigna unguiculata L.) and its F1 hybrids, Tikrit Journal for Agricultural Sciences, 23(4): 1-10.

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Pandey S., Shrestha S., Gautam I., Dhakal M., and Sapkota S., 2020, Evaluation of yard long bean (Vigna unguiculata ssp. sesquipedalis) genotypes for commercial production in the central mid hills region of Nepal, Nepal Horticulture Journal, 14(1): 43-47.

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Pierre J., Singh U., Latournerie-Moreno L., Garruña R., Jacobsen K., Ruíz-Santiago R., Chan-Arjona A., and Ruíz-Sánchez E., 2024, Effect of different maize (Zea mays)/cowpea (Vigna unguiculata) intercropping patterns and N supply on light interception, physiology and productivity of cowpea, Agricultural Research, 13(1): 204-215.

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Poudel B., Chaudhary G., Bhatt A., and Neupane S., 2024, Effect of spacing and different levels of phosphorus on growth and yield of Malepatan-1 variety of cowpea (Vigna unguiculata (Linn.) Walp.) in Dang district, Nepal, Advances in Agriculture, 2024: 9394237.

https://doi.org/10.1155/2024/9394237

Putra D., Wibowo L., Ginting Y., and Sa'diyah N., 2024, Korelasi antar karakter hasil lima varietas tanaman kacang panjang (Vigna sinensis) di lingkungan organik, Jurnal Agrotropika, 23(1): 45-52.

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Ramanjineyulu M., Vaishnavi S., Basavaraj T., Reddy S., Rao M., Sathish B., and Sravya G., 2025, Optimisation of nutrient sources for improving growth, yield, and quality of yardlong bean (Vigna unguiculata subsp. sesquipedalis L.), Asian Journal of Soil Science and Plant Nutrition, 11(4): 583.

https://doi.org/10.9734/ajsspn/2025/v11i4583

Ramkumar K., 2021, Genetic variability, heritability and genetic advance studies in yardlong bean (Vigna unguiculata spp. sesquipedalis) genotypes, Annals of Plant and Soil Research, 23(2): 215-220.

https://doi.org/10.47815/apsr.2021.10060

Sahu D., and Verma A., 2020, Effect of plant growth regulators on growth and yield of yard long bean (Vigna unguiculata L.) var. Shefali, International Journal of Chemical Studies, 8(6): 11016.

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Santos M., Linhares P., Dantas T., de Sousa Alves L., Sousa R., Silva U., Rodrigues W., Pereira J., Sampaio P., da Costa D., Alves D., de Medeiros J., and de Lima Cipriano Carlos I., 2024, Effect of plant density on yield and yield components of cowpea (Vigna unguiculata L.) in the semi-arid region of Brazil, Asian Journal of Research in Crop Science, 9(2): 274.

https://doi.org/10.9734/ajrcs/2024/v9i2274

Sartika D., Taryono T., and Sayekti R., 2020, The effect of the stake structure models on pod quality of several yardlong bean varieties, Agrotechnology Innovation (Agrinova), 3(1): 1-8.

https://doi.org/10.22146/a.58351

Sharma T., Singh J., Madaik S., Kumar P., Singh A., Rana B., and Chauhan G., 2024, Organic input incorporation for enhancing sustainability and economic viability of cowpea in north-western Himalayan region, Frontiers in Agronomy, 6: 1458603.

https://doi.org/10.3389/fagro.2024.1458603

Shrestha S., Yadav P., Khanal B., Bhujel P., Neupane A., Chaudhary B., and Giri D., 2023, Effect of Rhizobium leguminosarum inoculation and mulching on growth and yield of Chinese long bean (Vigna unguiculata subsp. sesquipedalis), AgroEnvironmental Sustainability, 1(3): 301.

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Sindhuja G., Patro T., Suneetha D., Emmanuel N., and Chennkesavulu B., 2021, Effect of integrated nutrient management on yield and quality of yardlong bean (Vigna unguiculata (L.) Walp. ssp. sesquipedalis Verdc.), International Journal of Chemical Studies, 9(2): 11948.

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Sultana Z., Ahmed N., Islam M., and Rahim A., 2021, Genetic variability and yield components of yard long bean (Vigna unguiculata var. sesquipedalis L.), Agronomski Glasnik, 82(3): 215-224.

https://doi.org/10.33128/ag.82.3.2

Suma A., Latha M., John J., Aswathi P., Pandey C., and Ajinkya A., 2021, Yard-long bean, in: The Beans and the Peas, Elsevier, pp. 201-226.

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Tewodros A., Mélèse L., and Yoseph T., 2021, Assessment of the production and importance of cowpea (Vigna unguiculata (L.) Walp): cases from selected districts of southern Ethiopia, African Journal of Food, Agriculture, Nutrition and Development, 21(6): 18030-18045.

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Thi T.T., Phuong T.T., Van Pham T., and Nguyen T.T., 2025, Effects of nutrient solutions on growth, yield and quality of yardlong bean plant (Vigna unguiculata subsp. sesquipedalis L.) grown in a hydroponic system, Horticultural Science, 52(1): 1-8.

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Zhang N., Liu L., Li H., Wei W., Liang G., Tang Y., Zhao Y., Wei O., and Yang Q., 2024, Effects of protected cultivation on agronomic, yield, and quality traits of yard-long bean (Vigna unguiculata ssp. sesquipedalis), Horticulturae, 10(11): 1167.

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