1 Introduction

Soybean (Glycine max (L.) Merr.) is one of the world’s most important legume crops, valued for its high protein and oil contents and broad use in food, feed, and industrial products (Hamza et al., 2024). Among diverse seed coat colors, black soybean has attracted increasing attention because of its superior nutritional profile and abundant bioactive compounds compared with the widely cultivated yellow soybean (Li et al., 2024). However, modern production systems have historically prioritized yield and disease resistance, contributing to a decline in the cultivation and utilization of black soybean despite its nutritional and functional advantages (Mitharwal et al., 2024). Understanding how cultivation practices affect the quality characteristics of black soybean is therefore essential for simultaneously meeting market demand for high-value functional foods and supporting sustainable crop production (Bellaloui et al., 2020; Chețan et al., 2021).

Black soybeans are rich in proteins, essential amino acids, lipids, dietary fiber, minerals, and a wide range of phytochemicals such as anthocyanins, isoflavones, phenolic acids, and tocopherols, which together confer strong antioxidant and multiple health-promoting properties (Kumar et al., 2022). The black seed coat in particular is a major reservoir of polyphenols, including cyanidin-3-O-glucoside and other anthocyanins, that contribute disproportionately to antioxidant capacity and potential protective effects against chronic diseases (He et al., 2023). Nonetheless, the composition of proteins, oils, minor nutrients, and bioactive compounds in black soybean is not fixed; it varies among genotypes and is strongly influenced by environmental conditions and agronomic management (Mitharwal et al., 2024). This variability highlights the need to systematically characterize black soybean quality traits and their determinants to guide both breeding and cultivation strategies (Bellaloui et al., 2020).

The quality characteristics of soybean seeds are typically described in terms of protein, oil, fatty acid profile, sugars, minerals, and bioactive components, all of which are crucial for nutritional value and processing performance. In black soybean, seed size and genetic background affect levels of anthocyanins, isoflavones, total phenolics, and antioxidant activities, indicating that genetic factors and seed morphological traits are key regulators of functional quality (Choi et al., 2020）. At the same time, environmental variables such as temperature, sunshine hours, diurnal temperature range, and soil moisture significantly alter protein and oil contents, fatty acid composition, and some mineral concentrations, reflecting complex climate-quality relationships. For example, water or heat stress can reduce protein and certain sugars while increasing oil or specific fatty acids, and large climatic gradients can differentially shape metabolite profiles among producing regions (He et al., 2023).

Beyond genetic and climatic influences, cultivation and management practices play a critical role in regulating soybean seed composition and quality. Multi-environment analyses and field experiments show that planting date, seeding rate, row spacing, fertilization, and tillage systems can significantly modify protein and oil concentrations, fatty acid profiles, sugars, fibers, and mineral contents (Chețan et al., 2021). Late sowing, high plant density, or suboptimal nutrient supply often shift the balance between protein and oil or alter specific quality components, demonstrating that management decisions can be used as tools to fine-tune grain composition. Studies have also reported that fertilization regimes and seeding rates affect protein and fiber content, and that different tillage and sowing methods influence nutrient composition and stability of protein and fat yields across environments (Faligowska et al., 2025). However, most of these findings are derived from yellow soybean or mixed-color materials, and there is limited systematic information on how different cultivation practices specifically regulate the quality traits of black soybean. Addressing this gap is essential to develop targeted agronomic strategies that enhance the nutritional and functional value of black soybean while maintaining agronomic performance (Li et al., 2024).

2 Theoretical Basis and Evaluation Indicator System

2.1 Physiological-ecological mechanisms of black bean quality formation

Seed quality is physiologically determined by assimilate partitioning and nutrient transport to the grain, which are strongly modulated by temperature, water status, and soil fertility during seed filling. Protein and oil show large environmental variance, with site-year explaining most variation, indicating that ecological conditions (heat, drought, latitude) dominate over management in shaping baseline composition.

In black soybeans, pigments and antioxidants (anthocyanins, isoflavones, phenolics) in the seed coat respond to both genetic background and ecological stress signals, such as light and nutrient status (Liang et al., 2025). Anthocyanin and related antioxidant systems are linked to stress-response pathways, and low nitrogen can induce marked increases in anthocyanin metabolites and expression of flavonoid-pathway genes in black seed coats (Yeom et al., 2024).

2.2 Construction of quality evaluation indicators (appearance, nutrition, and processing characteristics)

Appearance indicators include seed size, seed coat color, and visible defects, all of which are linked to underlying biochemical traits. In black soybeans, seed coat color and intensity reflect anthocyanin accumulation, and colored seed coats (black vs brown vs green) differ strongly in protein, oil, sugars, and antioxidant components (Dhungana et al., 2021; Wang et al., 2025). Seed weight classes (small, medium, large) also show systematic differences in anthocyanins, isoflavones, phenolics, and antioxidant activities, making 100-seed weight a useful integrative appearance-quality indicator (Choi et al., 2020).

Nutritional indicators should minimally cover protein, oil, fatty acid profile, sugars, minerals, and key bioactives. Colored and specifically black soybeans show wide ranges in protein (≈39-43%), oil (≈14-20%), anthocyanins, isoflavones, polyphenols, and antioxidant capacity, which define their functional value (Mitharwal et al., 2024). For oil, indices such as PUFA/MUFA/SFA ratios, atherogenicity/thrombogenicity indices, and oxidizability provide finer evaluation of health-related quality (Baisch et al., 2024).

Processing-related indicators include protein quality, oil stability, hydration and physical properties, and responses to processing. Across soy products, digestible amino acid-based scores (DIAAS, PDCAAS) are high but vary with processing and post-processing, indicating that protein quality is a sensitive processing-quality indicator (Van Den Berg et al., 2022). Physico-chemical traits (seed size/shape, bulk density, hydration and swelling capacity, color parameters) determine sorting, dehulling, milling, and rehydration performance, while processing can enhance protein, fiber, vitamins and reduce antinutritional factors, improving overall functional quality (Cai et al., 2021; Chuwa et al., 2023).

2.3 Mechanisms by which cultivation measures influence quality

Cultivation practices (fertilization, planting date and density, tillage, cover crops, inoculation, and foliar inputs) modify canopy microclimate, root activity, and nutrient supply, thereby altering seed composition. Large multi-environment analyses show that delayed planting tends to reduce oil and increase protein, and that moderate nitrogen can raise both protein and oil, underscoring the role of management in fine-tuning composition within strong environmental constraints. Seeding rate and row configuration also modify competition and resource capture, leading to significant shifts in protein, fatty acids, sugars, and mineral contents (Bellaloui et al., 2020).

Soil and residue management change nutrient availability and stress conditions, influencing both major nutrients and more subtle quality indices. In lowland systems, soil preparation and cover crops (e.g., scarification plus ryegrass) increase yield and raise protein, oil, and macro-/micronutrient contents in grains and oil quality indices (Baisch et al., 2024). Tillage systems and fertilizer strategies similarly affect protein and fiber content, while combined fertilization and biological treatments (e.g., mycorrhiza-forming agents, foliar organo-mineral fertilizers) enhance the intensity and yield of crude protein and oil per hectare, linking cultivation technology directly to economic quality outputs (Holodna and Hrytsiuk, 2025).

3 Experimental Design and Technical Roadmap

3.1 Conditions of the experimental area and rationale for material selection

The experiment is planned in a typical black soybean production area with stable climatic conditions suitable for soybean growth, characterized by warm summers, sufficient accumulated temperature, and moderate precipitation, similar to major soybean regions where yield and quality are sensitive to year-to-year weather variation (Kočar et al., 2022). Soil properties (texture, pH, organic matter, and available N, P, K) will be characterized before sowing to clarify baseline fertility, following approaches used in long-term soybean field trials where soil status strongly conditions responses to fertilization and water management (Li et al., 2022). Such detailed site characterization helps to distinguish treatment effects from environmental noise and allows extrapolation of results to agro-ecological zones with comparable climatic and edaphic backgrounds (Figure 1) (Chețan et al., 2021).

Figure 1  Research framework for the selection of black bean experimental zones and variety configuration

Black soybean cultivars will be chosen based on their wide local adoption, contrasting seed quality traits, and documented responsiveness to cultivation area or sowing date, which strongly affect proximate composition and antioxidant activity in black soybean (Lee et al., 2021). Previous studies demonstrated that black soybean cultivars differ significantly in crude protein, fat, dietary fiber, polyphenols, and radical scavenging capacity across cultivation sites and seeding periods, confirming that genotype-environment interactions are crucial for quality expression. Selecting locally representative, high-value black cultivars therefore ensures both practical relevance for regional production and sufficient genetic variation to reveal how cultivation practices modulate key quality attributes.

3.2 Design of cultivation measures and comparison schemes (planting density, fertilization, irrigation, etc.)

The experiment will adopt a split-plot or multifactorial randomized block design to evaluate main cultivation factors and their interactions, following soybean studies that combined year, tillage, fertilization level, and seeding rate in multi-factor schemes (Chețan et al., 2021). Main plots will be assigned to irrigation regimes (rainfed, deficit, and full irrigation) to reflect differences in soil water availability, while subplots and sub-subplots will combine planting density and fertilization rate, similar to designs testing plant density × N rate × irrigation under ridge-furrow plastic mulching (Liao et al., 2022). Replications will be arranged to control field heterogeneity and ensure adequate statistical power to detect differences in yield and quality traits.

Planting density treatments will span a range from relatively low to relatively high stands, reflecting densities that have been shown to alter yield, morphological traits, and protein and oil content in soybean. Fertilizer treatments will include a no-fertilizer control and graded N-P-K combinations, drawing on evidence that N and compound fertilization significantly affect yield, biomass, and harvest index, with more limited but still relevant effects on seed quality (Franco et al., 2025). Irrigation treatments will consist of rainfed, deficit irrigation (e.g., maintaining soil water at around 60% of field capacity), and full irrigation (80%-100% of field capacity), reflecting studies showing that irrigation level modifies grain yield and grain protein and oil contents in interaction with environmental conditions and genotype (Pinnamaneni et al., 2021).

3.3 Technical roadmap and data processing methods

The technical roadmap follows a sequence of site preparation, treatment application, sampling, and data analysis. After pre-season soil testing and field layout, black soybean will be sown at designated densities and fertilization regimes, and irrigation will be scheduled and monitored to maintain target soil moisture levels, similar to drip-irrigated and deficit-irrigated soybean experiments (Li et al., 2022). During the growing season, agronomic traits (emergence, plant height, branching, pod number, and biomass) will be recorded, and at maturity, yield and yield components will be measured, following protocols widely used in density, fertilization, and irrigation studies on soybean (Liao et al., 2022). Harvested seeds will be analyzed for moisture, protein, oil, and key functional components to quantify quality responses to the different cultivation practices (Lee et al., 2021).

Data will be processed using analysis of variance (ANOVA) appropriate for split-plot or multifactorial designs to test main effects and interactions of planting density, fertilization, and irrigation on yield and quality traits, as in previous work on soybean management and grain composition. Where necessary, regression or response-surface models will be fitted to describe quantitative relationships between fertilization rate, water supply, and target variables, similar to approaches used to optimize fertilization combinations under drip irrigation (Franco et al., 2025). Experimental precision will be assessed using standard statistics (e.g., coefficients of variation), and sample sizes per plot will follow recommendations that stabilize confidence intervals for plant-level counting traits, thereby ensuring reliable estimation of treatment effects on black soybean quality (De Souza et al., 2023).

4 Impact of Different Cultivation Measures on the Appearance Quality of Black Beans

4.1 Grain size and uniformity

Grain size is a core appearance trait that also reflects physiological vigor and yield potential. Large and medium soybean seeds show higher germination potential, seedling vigor, leaf area, dry matter accumulation, and ultimately greater 100-seed weight and yield than small or very small seeds, indicating that grain size is closely linked to plant growth performance and final productivity (Wang et al., 2025; Sacramento et al., 2020). In black soybean, seed weight classes (small, medium, large) are also associated with distinct profiles of anthocyanins, isoflavones, phenolics, and antioxidant activities, so selecting for larger grains can simultaneously improve visual appearance and functional quality (Choi et al., 2020).

Cultivation measures that modify plant density and spatial distribution strongly affect grain size and size uniformity. Higher and more uniform plant spacing improves canopy light interception and dry matter accumulation, thereby increasing mean seed weight and markedly reducing plant-to-plant variation in seed weight per plant, which enhances uniformity of marketable grains (Jańczak-Pieniążek et al., 2021). Row spacing and density combinations also influence 100-grain weight, with narrower rows at higher densities often achieving both higher yield and relatively stable 100-grain weight, although excessive density can reduce pods per plant and partially offset size gains (Ran et al., 2023).

4.2 Grain color and seed coat characteristics

Black seed coat color and intensity are determined by accumulation of pigments such as anthocyanins and flavan-3-ols, which are major contributors to antioxidant activity and functional value. Comparative analyses of mutant lines with different seed coat colors show that black seed coats contain multiple anthocyanins and high flavan-3-ol levels, conferring much stronger antioxidant activity than yellow or pale coats where anthocyanins are absent (Lim et al., 2021; Jo et al., 2021). Within black soybean germplasm, seed coat color type (e.g., black with green cotyledons) is linked to specific anthocyanin compositions and chlorophyll contents, which underlie both visual attributes and perceived health benefits in markets (Choi et al., 2020).

Cultivation practices can indirectly influence color expression and seed coat integrity through their effects on grain filling conditions and plant health. Adequate plant distribution and resource supply promote stable pigment synthesis and reduce weathering or mechanical damage on the seed surface, thereby maintaining uniform dark coloration and glossy appearance (Figure 2) (Xu et al., 2021). Conversely, suboptimal density or nutrient stress can lead to uneven pod exposure, microclimate heterogeneity, and increased incidence of discolored, shriveled, or cracked seeds, lowering visual quality even when genetic potential for black pigmentation is present (Hao et al., 2023).

Figure 2  Mechanism of black bean seed coat color formation and its relationship with cultivation management and quality

4.3 Analysis of commercial quality evaluation indicators

Commercial appearance evaluation of black beans focuses on grain size distribution, uniformity, color consistency, cleanliness, and visible defects. Studies grouping black soybeans into small, medium, and large classes demonstrate that 100-seed weight can serve as a practical index for grading, because it correlates with both visual size classes and bioactive composition, helping to differentiate high-value lots (Jiang et al., 2023). Seed shape traits such as length, width, perimeter, projection area, and length-width ratio, controlled by multiple QTLs, also contribute to appearance grading and can be objectively measured to support standardized commercial specifications (Li et al., 2020).

Cultivation measures that optimize row spacing and seeding rate improve not only yield but also key commercial indicators. Higher, well-managed densities increase canopy closure and reduce intra-field variability, favoring more uniform grain size and fewer undersized seeds, while certain spacing combinations enhance 100-seed weight and reduce lodging or disease that create damaged or stained grains (Ran et al., 2023). At the same time, appropriate fertilization and water management support full seed filling and intact seed coats, decreasing the proportion of broken, shriveled, or discolored seeds that are heavily discounted in grading standards (Liao et al., 2022; Hao et al., 2023).

5 Impact of Different Cultivation Measures on the Nutritional Quality of Black Beans

5.1 Variations in protein and lipid content

Protein and oil are the core nutritional traits in black soybean and are highly sensitive to cultivation practices. Manipulating plant density and nitrogen fertilization alters canopy competition and N supply, thereby changing grain protein and oil levels. In soybean, moderate mineral N input can slightly adjust protein and oil, while very high density may reduce assimilate supply per plant and depress oil accumulation. Field experiments combining tillage, graded N-P fertilization, and seeding rate further show that higher fertilization rates and intermediate-high plant densities raise grain protein content, confirming that nutrient input interacts with stand structure to regulate seed protein deposition (Bellaloui et al., 2020).

In black soybean grown on acid soil, combined application of dolomitic lime and NPK fertilizers significantly increased yield and total dissolved protein content, reflecting improved nutrient availability and alleviation of aluminum and manganese toxicity. The highest protein content was obtained at an intermediate lime rate (4.5 t/ha), indicating that over-liming or excessive fertilizer can impair growth and quality (Soeparjono and Kadiyasari, 2021). Across colored soybeans, genotypic differences also create a wide baseline range of 38.9%-43.3% protein and 13.9%-20.4% oil, suggesting that cultivation measures act on a genotype-dependent potential when modifying protein-oil balance (Dhungana et al., 2021).

5.2 Soluble sugar and amino acid composition

Cultivation practices that affect canopy structure and N supply can modify both seed sugars and amino acids. In irrigated soybean, seeding rate, row spacing, N fertilization, and herbicide treatment significantly changed contents of sucrose and other sugars, as well as several amino acids, with moderate seeding rate and adequate N leading to higher protein, oleic acid, some sugars, and some amino acids than very high density. Nitrogen application increased protein and linolenic acid and enhanced some amino acids, whereas excessive density reduced sugars and amino acids due to intensified nutrient competition (Bellaloui et al., 2020).

Across soybean germplasm, large natural variation in soluble sugars (≈84.7-140.9 mg/g) and water-soluble protein (26.5%-36.0%) has been documented, and higher soluble protein correlates positively with total water-soluble sugar and sucrose, but negatively with glucose and fructose (Yu et al., 2016). Vegetable soybean varieties also differ widely in sugar (15.1-34.0 mg/g) and total free amino acid contents (4.6-10.2 mg/g), with some cultivars being particularly rich in sucrose or specific amino acids such as asparagine and alanine. These findings suggest that, in black soybean, optimizing density and N while choosing appropriate cultivars can be used to steer sweetness and amino acid balance toward targeted nutritional profiles.

5.3 Variations in functional component content (e.g., anthocyanins, polyphenols)

Functional components in black soybean—anthocyanins, proanthocyanidins, isoflavones, and other polyphenols—are strongly influenced by both nutrient management and light environment. In hydroponically grown black soybean, low nitrogen (1.5 mmol/L) markedly increased the number and abundance of anthocyanin metabolites in seed coats, accompanied by upregulation of key biosynthetic genes (e.g., DFR, OMT) and antioxidant-related pathways. This indicates that moderate N deficiency can act as a signal to enhance anthocyanin accumulation and antioxidant capacity in black soybean seeds (Liang et al., 2025). More broadly, a review of vegetables and fruits shows that lower mineral N fertilization often increases total polyphenols, whereas heavy fertilization tends to reduce phenolic levels, emphasizing the importance of restrained N supply for maximizing polyphenol content.

Light regime associated with cultivation systems also modulates functional components. In black soybean, spatiotemporal shading from relay intercropping or controlled shade treatments significantly altered anthocyanin, proanthocyanidin, and sucrose contents across seed developmental stages (Dennis et al., 2020). Relay intercropping produced the highest anthocyanin concentrations in mature seeds, while shading during the vegetative stage maximized proanthocyanidin and improved sucrose at later stages, showing that specific shading windows can enhance multiple functional traits simultaneously. At the genotype level, black seed-coated soybeans exhibit much higher total anthocyanins, polyphenols, flavonoids, and antioxidant activity than brown or green types, but still show large within-black variation, providing scope for combining optimized cultivation with cultivar selection to achieve superior functional quality (Li et al., 2024).

6 Impact of Different Cultivation Measures on the Processing and Edible Quality of Black Beans

6.1 Water absorption and cooking characteristics

Water absorption during soaking determines subsequent cooking rate, texture, and solids loss. Hydration studies on soybeans, including black types, show that higher soaking temperature markedly accelerates water uptake but also increases leaching of soluble solids, proteins, and sugars, which can influence flavor and nutritional retention after cooking. Kinetic analyses further indicate that hydration is a non-spontaneous process whose rate rises with temperature; black soybeans reach high ultimate hardness after cooking compared with yellow soybeans, implying that both intrinsic structure and hydration behavior together shape final softness and mouthfeel (Wang et al., 2021).

Genetic differences among black soybean lines also result in wide variation in hydration capacity, hydration index, swelling capacity, and required cooking time, demonstrating strong genotype control over basic cooking quality. Quantitative trait locus (QTL) analyses in black soybean have identified loci associated with seed water absorption ratio and hardness after cooking with rice, suggesting that both seed coat and cell-wall related genes (e.g., peroxidase, pectin-methylesterase inhibitor) regulate water penetration and softening behavior (Heo et al., 2022). These findings imply that cultivation measures modifying seed size, composition, or seed coat integrity may indirectly influence soaking and cooking traits through their impact on these physiological and structural determinants.

6.2 Textural quality and flavor characteristics

Texture of cooked or processed black soybean products depends on hydration, cell-wall properties, and matrix structure. For boiled black soybeans, sensory hardness and viscosity correlate with objective texture-analyzer measurements and with pectic solubility and mineral composition, allowing physical and chemical indices to substitute for subjective sensory evaluation when screening many lines. In black soybean cooked with rice, seed hardness varies among recombinant inbred lines, and different QTLs control hardness in distinct genetic backgrounds, indicating that textural quality is a complex trait influenced by multiple loci and potentially responsive to environmental and cultivation conditions (Heo et al., 2022).

Flavor characteristics of soybean are determined by amino acid composition, soluble sugars, and volatile compounds formed during heating. Studies on vegetable soybeans show that varieties with higher soluble protein, soluble sugars, and umami free amino acids receive higher sensory scores for taste and overall acceptability, with texture (tenderness, waxiness) also strongly affecting preference (Figure 3) (Guo et al., 2022). Processing of black soybean into miso enhances taste intensity and functionality, with black soybean miso showing higher protein, organic acids, basic amino acids, minerals (K, P, Fe, Zn), γ-aminobutyric acid, and polyphenols than yellow soybean miso, which supports the development of richly flavored, health-oriented fermented products from appropriately grown black beans.

Figure 3 Mechanisms of formation and influencing factors of black bean processing quality (texture and flavor)

6.3 Processing adaptability and product development potential

Differences in physicochemical traits among black soybean lines translate into distinct processing suitability. Evaluation of 20 black-seeded lines revealed large variation in hardness, hydration capacity, swelling behavior, protein, oil, minerals, and antinutritional factors, and some genotypes combined fast cooking with high protein and favorable mineral profiles, making them good candidates for pulse-type products or as raw material for processing under diverse conditions. A systematic review further highlights that processing operations such as soaking, thermal treatment, and fermentation can reduce antinutritional factors and modify nutritional and bioactive profiles, suggesting that lines selected and cultivated for specific compositions can be matched with tailored process conditions to optimize edible quality and health benefits (Li et al., 2024).

Black soybean also shows broad potential in novel products and ingredient systems. Use of black soybean flour in cookies significantly improves protein quality, resistant starch, and slowly digestible starch, while particle size modification tunes physicochemical and texture attributes, demonstrating adaptability to baked goods (Yang et al., 2022). In addition, black soybean cooking water, an up-cycled by-product of paste production, exhibits strong foaming, emulsifying, binding, and texturizing abilities, allowing its powder to replace methylcellulose as a clean-label structuring agent in vegan patties, where it reduces cooking loss, enhances binding capacity, and increases hardness and adhesiveness (Echeverria-Jaramillo and Shin, 2023). Aligning cultivation practices to secure stable composition and functionality thus underpins the expansion of black soybean into high-value processed and functional foods.

7 Case Study: Comprehensive Analysis of the Impact of Typical Cultivation Models on Black Bean Quality

7.1 Cultivation models and management measures in the case study area

In the case study area, local producers adopt several representative soybean cultivation models that differ in tillage intensity, fertilization strategy, and planting density. A common “conventional intensive” model relies on full tillage with mineral NPK as a base fertilizer and sometimes a second N application at vegetative stages, often in combination with relatively high seeding rates to secure yield stability under variable weather. In contrast, “eco-oriented” or organic-type models emphasize reduced external inputs, biological nitrogen fixation, and improved soil structure, aiming to maintain yield with fewer chemical fertilizers and herbicides (Grabovskyi et al., 2023).

More recently, optimized technologies integrating biological products and precise input timing have been tested. One such model combines moderate mineral fertilization (e.g., N15P45K60 + N30) with pre-sowing seed treatment by mycorrhiza-forming and dressing agents, plus foliar organo-mineral fertilizers at key stages, to enhance both yield and grain quality (Holodna and Hrytsiuk, 2025). In water-limited regions, water-nitrogen optimized models under ridge-furrow or drip irrigation adjust irrigation quota and N rate simultaneously to improve canopy photosynthesis, grain yield, and seed protein and oil yield while maintaining resource-use efficiency (Liao et al., 2025).

7.2 Comparison of quality indicators under different treatments

Comparative trials show that intensive, biologically enhanced models can significantly increase protein and oil yield per hectare relative to simple fertilization or untreated controls. Under a technology combining N15P45K60 + N30 with mycorrhiza-forming seed treatments and foliar organo-mineral fertilizer, crude protein and oil yields reached 1.35 t/ha and 0.82 t/ha, respectively, with daily accumulation intensities of 12.27 and 7.45 kg/ha, clearly exceeding the absolute control (Holodna and Hrytsiuk, 2025). When foliar application was extended to both branching and budding stages, total protein and oil accumulation intensity in seeds increased by about 22%-24%, highlighting the strong effect of integrated nutrient-biological management on quality formation (Figure 4).

Figure 4 New ICT based fertility management model in private dairy farm India as well as abroad

At the same time, multi-objective optimization studies in semi-arid regions indicate that the “locally traditional” management (flat cultivation, higher N, lower seeding rate) can be inferior to optimized ridge-furrow with film mulch, reduced N, and higher seeding rate. The RWN30D32 model (ridge-furrow with mulch and supplemental irrigation, 30 kg N/ha, 320,000 plants/ha) improved canopy photosynthetic capacity, biological yield, grain yield, and seed protein and oil yield compared with the local NMN60D16 strategy, while slightly reducing protein and oil concentrations (Liao et al., 2025). This suggests important trade-offs between concentration and total nutrient yield when comparing cultivation models.

7.3 Evaluation of the effectiveness of optimized cultivation measures

Evaluation of optimized models must integrate agronomic, economic, and environmental dimensions. Fuzzy comprehensive evaluation of water-nitrogen-density combinations has shown that treatments like RWN30D32 can simultaneously maximize grain yield, economic return, and resource-use indices such as water productivity and partial factor productivity of nitrogen, thus ranking highest in overall performance despite modest declines in seed protein and oil percentages (Liao et al., 2025). Similarly, in the forest-steppe case, the technology combining moderate NPK, mycorrhiza-forming seed treatment, and foliar organo-mineral fertilization achieved the highest composite outcome in crude protein and oil yield per hectare and in their daily accumulation intensity, clearly outperforming simpler fertilization schemes.

Taken together, these case-based comparisons indicate that optimized cultivation models—characterized by coordinated fertilization, biological inputs, and rational water and density management—can substantially improve black soybean quality in terms of protein and oil yield per unit area without severely compromising concentration-based indicators. When selecting and promoting such models in a given black-bean region, priority should be given to those that couple high seed protein and oil yields with improved water- and nitrogen-use efficiency, thereby achieving both quality enhancement and sustainable resource use (Holodna and Hrytsiuk, 2025).

8 Conclusions and Outlook

Black soybean combines high protein, essential amino acids, lipids, dietary fiber, minerals, and abundant anthocyanins and polyphenols, giving it clear advantages over common yellow soybean as a functional food raw material. Comparative studies across cultivars, crop years, and cultivation areas show that contents of isoflavones, anthocyanins, protein, oil, and dietary fiber vary widely, confirming that both genotype and environment decisively shape nutritional and functional quality.

Field experiments on soybean demonstrate that fertilization level, planting density, and tillage system significantly influence yield and protein content, while climatic variation between years further modifies quality traits. For black soybean specifically, differences in cultivation area alter dietary fiber, phytic acid, antioxidant capacity, and enzyme inhibition activities, indicating that cultivation practices and site conditions affect not only basic composition but also physiological functions related to health value.

For high and stable yield with good quality, cultivation systems should adopt optimized combinations of planting density and N-P-K fertilization rather than relying on experiential management. Regression and “3414” fertilization trials suggest that intermediate-high densities with balanced N, P, and K maximize yield and biomass while maintaining desirable protein and oil traits under drip or conventional irrigation. In black soil regions, emphasis on soil physical improvement (bulk density, porosity, water holding) is also critical because soil physical properties exert the strongest positive effect on soybean yield at the catchment scale.

Future work should link detailed cultivation factors (density, fertilization, water regime, soil amendments) with comprehensive quality profiles, including proteins, lipids, sugars, amino acids, and key phenolics. Long-term, multi-site trials in black soil and other major producing areas would clarify how soil physical and chemical properties interact with management to control both yield and bioactive composition in black soybean. Integrating process-oriented quality indicators (hydration, cooking behavior, texture, flavor) with agronomic data would further guide cultivation tailored to specific product chains.

On the application side, black soybean’s rich profile of anthocyanins, phenolic acids, and isoflavones offers wide prospects for functional foods, biodegradable packaging, and therapeutic ingredients. Advances in gentle extraction, microencapsulation, and novel processing (e.g., natto, films, microcapsules) can greatly enhance stability, bioavailability, and product diversity, but require raw material with consistent quality supplied by optimized cultivation models. Closer coupling of breeding, agronomy, and food technology will therefore be central to fully exploiting the nutritional and health value of black soybean in future agri-food systems.

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 author affirms 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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