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Article

Effects of Biochar Combined with Organic Fertilizer on Soil Properties and the Yield and Quality of Sweet Potato

by
Guangyan Sun
1,2,
Zhenpeng Deng
1,2,
Ruina Zhao
1,2,
Fangxi Zhao
1,2,
Tenglong Wang
1,2,
Yucui Li
1,2,
Yiming Song
1,2,3,
Shuwen Deng
1,2,3,
Kang Du
1,2,
Changwen Lyu
1,2,
Daobin Tang
1,2,* and
Jichun Wang
1,2,3,*
1
College of Agronomy and Biotechnology, Southwest University, Chongqing 400715, China
2
Key Laboratory of Biology and Genetic Breeding for Tuber and Root Crops in Chongqing, Beibei, Chongqing 400715, China
3
Yibin Academy of Southwest University, Yibin 644000, China
*
Authors to whom correspondence should be addressed.
Horticulturae 2026, 12(2), 235; https://doi.org/10.3390/horticulturae12020235
Submission received: 3 January 2026 / Revised: 9 February 2026 / Accepted: 12 February 2026 / Published: 14 February 2026
(This article belongs to the Section Plant Nutrition)
Browse Figures
Versions Notes

Abstract

Biochar and organic fertilizers are recommended for sustaining crop yield and sustainable agricultural development. However, the mechanisms of their combined application on the nutritional, flavor and eating quality and their optimal ratio remain unclear in sweet potatoes. Therefore, this field experiment employed four fertilization treatments: inorganic compound fertilizer (CF), organic fertilizer (OF), and biochar-based organic fertilizer containing 15% biochar (BOF15) or 30% biochar (BOF30). The results revealed that the OF, BOF15, and BOF30 treatments significantly ameliorated soil physical properties, elevated soil pH values and available nutrient contents compared with CF. They also increased sweet potato yield, regulated sucrose-metabolizing enzyme, and enhanced quality. Among them, the BOF15 treatment exhibited the most significant improvement. Compared with CF, BOF15 treatment increased the contents of starch, total soluble sugar, sucrose, and β-carotene by 23.16–31.82%. It also optimized texture by reducing hardness and chewiness while increasing springiness, elevated key volatile compounds (terpene and aldehyde), and received the highest sensory scores for mealiness, aroma, and sweetness. In conclusion, biochar combined with organic fertilizer synergistically improves soil properties and enhances sweet potato yield and quality, with BOF15 being the optimal treatment. This study provides support for optimizing fertilization strategies in high-quality sweet potato production.

1. Introduction

Sweet potato (Ipomoea batatas Lam.) is an important food and economic crop globally with multiple uses in fresh consumption, processing, and biomass energy production. In China, the sweet potato cultivation area reached 2.32 million hectares in 2023, with a total yield of 51.63 million tons, securing its position as the world’s top producer [1]. Sweet potato storage roots are abundant in starch, protein, and a variety of bioactive constituents, including polyphenols, flavonoids, and β-carotene [2]. These components not only confer health-promoting effects such as antioxidant, anti-inflammatory, and insulin-sensitivity-regulating properties but also directly shape flavor characteristics [3,4,5]. Meanwhile, the texture of the storage roots is a key determinant of eating quality. Lignin, as a critical structural component of cell walls, regulates cell wall rigidity, thereby influencing storage root hardness and mouthfeel [6]. With the increasing awareness of healthy diets and shifting market demands, the nutritional value and flavor quality of sweet potatoes have become core factors influencing consumer choice and the sustainable development of the industry [7,8].
In sweet potato production, fertilization is an important agronomic practice for regulating yield and quality. However, long-term overuse of chemical fertilizers has given rise to a series of problems, including soil compaction, declining fertility, and declining crop quality [9,10]. Therefore, exploring environmentally friendly fertilization strategies that synergistically enhance crop yield and quality has become a key challenge for sustainable agricultural development. In this context, organic soil conditioners such as organic fertilizers and biochar have emerged as viable alternatives to traditional chemical fertilizers due to their environmental protection, high efficiency, and economic feasibility [11,12]. Biochar, with a porous structure and adsorption capacity, can enhance soil structure and improve soil water retention [13]. In addition, it enhances the efficiency of nutrient uptake and utilization in crops [14,15,16]. However, due to its low nutrient concentration and strong resistance to biodegradation, its use as a sole nutrient source may be limited [17]. Therefore, combining biochar with organic fertilizer in specific proportions to produce biochar-based organic fertilizer allows for complementary advantages. Organic fertilizers provide both rapid-release and slow-release nutrients, while biochar acts as a carrier and regulator, slowing nutrient loss and promoting balanced nutrient supply. This synergistic effect is expected to further optimize crop quality while improving soil health [18,19,20]. However, the strength of this synergistic effect is highly dependent on the biochar addition ratio and varies with crop species and soil conditions [21]. For instance, studies indicated that a mixture of biochar and organic fertilizer at a 30%:70% ratio resulted in the strongest synergistic effect for enhancing soil fertility and promoting plant growth [22]. Another study found that a 15% biochar addition ratio performed best when comprehensively considering vegetable yield and soil organic carbon sequestration [23]. Furthermore, studies have shown that a treatment with a 1:2 ratio (biochar: organic fertilizer) yielded the highest potato production [24].
While the impacts of biochar on soil fertility and crop growth have been extensively studied, its combined mechanism with organic fertilizer on the nutritional, flavor, and textural quality of sweet potato, and their optimal mixing ratio, remains unclear. Therefore, this study systematically studies the impacts of biochar-based organic fertilizer with different blending ratios (representing moderate and high biochar addition) on soil properties, sweet potato yield, and nutritional, flavor, and eating quality. It aims to elucidate the key mechanisms through which biochar-based organic fertilizer influences sweet potato quality, determine the optimal blending ratio for synergistic effects between biochar and organic fertilizer, and provide a scientific basis for identifying superior, sustainable organic fertilization alternatives to conventional mineral fertilizers. The findings are expected to offer guidance for the standardized production and field application of biochar-based organic fertilizer, thereby promoting high yield, premium quality, and sustainable development in the sweet potato industry.

2. Materials and Methods

2.1. Site Description

The field experiment was carried out from May 2023 to October 2024 at the experimental base of the Institute of Tuber and Root Crops, Southwest University in Chongqing, China (29°80′ N, 106°40′ E). This region experiences a subtropical monsoon climate, with an average annual temperature of approximately 18.11 °C, an annual average precipitation of 1099.99 mm, and an annual average frost-free period of 359 days. Figure 1 shows the meteorological conditions during the experimental period, with a daily average temperature of 27.18 °C and a total precipitation of 768.04 mm. The maximum temperature generally remained above 26 °C, mostly fluctuating between 26 °C and 39 °C, with significant variations from May to September, which gradually declined after late September. Precipitation was concentrated from late May to mid-July, with multiple instances of heavy rainfall during this period, which decreased significantly from late July to October. The field experiments in 2023 and 2024 were conducted on adjacent plots at the same location. The experimental soil was classified as Anthric Anthrosol according to the World Reference Base for Soil Resources (IUSS Working Group WRB, 2022) [25]. The basic soil properties for the experimental years were as follows. In 2023, the bulk density (BD) was 1.34 g cm−3, with a pH of 6.7, organic matter content of 24.01 g·kg−1, total nitrogen (TN) of 1.40 g·kg−1, total phosphorus (TP) of 0.81 g·kg−1, total potassium (TK) of 13.05 g·kg−1, alkali-hydrolyzable nitrogen (AN) of 1.40 mg·kg−1, available phosphorus (AP) of 12.33 mg·kg−1, and available potassium (AK) of 88.41 mg·kg−1. In 2024, the corresponding values were: bulk density, 1.40 g·cm−3; pH, 6.3; organic matter, 13.88 g·kg−1; TN, 1.28 g·kg−1; TP, 1.23 g·kg−1; TK, 10.86 g·kg−1; AN, 81.87 mg·kg−1; AP, 20.65 mg·kg−1; and AK, 63.12 mg·kg−1.

2.2. Experimental Design

A two-factor split-plot design was employed. The main plots consisted of two orange-fleshed sweet potato cultivars: Yuhongxinshu No. 3 (YHX3) and Yuhongxinshu 98 (YHX98). Both are fresh-eating types characterized by high carotenoid content and were bred and provided by the Tuber and Root Crops Research Institute of Southwest University. The subplots comprised four fertilizer treatments: inorganic compound fertilizer only (CF); 2337.55 kg·ha−1 organic fertilizer (replacing 30% inorganic N) combined with inorganic fertilizer (OF); 2337.55 kg·ha−1 biochar-based organic fertilizer (containing 15% biochar, w/w) combined with inorganic fertilizer (BOF15); and 2337.55 kg·ha−1 biochar-based organic fertilizer (containing 30% biochar, w/w) combined with inorganic fertilizer (BOF30). The CF treatment (representing the local conventional fertilization practice) served as the control to evaluate the advantages of all organic treatments (OF, BOF15, BOF30) as alternatives to the conventional fertilization regimen. To precisely isolate the effects of different biochar proportions (0%, 15%, 30%), the application rates of the biochar-based organic fertilizers in BOF15 and BOF30 treatments were kept identical to that of the organic fertilizer in the OF treatment, thus eliminating the interference of differences in the total input of organic materials on the results. Based on the inherent nutrient content of the organic and biochar-based organic fertilizers, inorganic fertilizers were added to ensure a consistent total NPK supply across all organic treatments, matching the CF treatment. This equal nutrient leveling method was adopted with reference to previous studies [26,27]. This design aims to strictly control the key variable of total nutrient supply, thereby focusing comparisons between treatments on the specific effects of biochar addition and its proportion. Meanwhile, sweet potato is a typical K-loving crop. This nutrient calibration strategy ensures a balanced nutrient supply required for sweet potato growth, fully meets their high K demand, thus preventing potential declines in yield and quality due to nutrient deficiency or imbalance derived from insufficient inherent nutrients in organic materials. The specific fertilization rates are detailed in Table 1.
The organic fertilizer (N-P2O5-K2O = 2.20-1.50-0.3, organic matter ≥ 30%), the biochar-based organic fertilizer containing 15% biochar (N-P2O5-K2O = 1.93-1.1-0.23, organic matter ≥ 30%), and the biochar-based organic fertilizer containing 30% biochar (N-P2O5-K2O = 1.4-0.9-0.21, organic matter ≥ 30%) were all purchased from Sichuan Shliwang Agricultural Technology Development Co., Ltd., Yibin, Sichuan, China. The raw materials for the organic fertilizer comprised camphor leaves and distiller’s grains. Biochar was produced by pyrolyzing camphor leaves in a traditional pyrolysis reactor. The biochar-based organic fertilizer was produced by blending the biochar with organic fertilizer at a specific ratio. The specific chemical properties of all fertilizers used are detailed in Table 2. The inorganic fertilizers used included compound fertilizer (N-P2O5-K2O = 16-5-21, Sichuan Bangruite Biotechnology Co., Ltd., Yibin, Sichuan, China.), urea (46% N, Sichuan Tianhua Co., Ltd., Luzhou, Sichuan, China.), and potassium sulfate (52% K2O, SDIC Xinjiang Lop Nur Potash Co., Ltd., Korla, Xinjiang, China). The biochar selected for this study represents a major agricultural waste resource in the region, and its utilization holds significant practical value. The biochar addition ratios in the organic fertilizer were set at 0%, 15%, and 30%. This gradient was designed with reference to the effective ranges commonly reported in relevant studies [21,22,23,24], covering moderate to relatively high addition levels. This gradient allows for the detection of potential dose-dependent effects or optimal thresholds of biochar addition. Furthermore, the selected ratios are feasible and economically viable in terms of field-scale organic fertilizer production, application costs, and agronomic operations. All organic fertilizer with or without biochar and 60% inorganic fertilizer was applied as a single basal application; the 40% inorganic fertilizer was top-dressed 20 days after transplanting (DAT). There were eight treatments, each with three replicates. Each plot was 20 m2 (2.7 m × 7.4 m), containing 120 plants with a plant spacing of 185 cm and a ridge spacing of 60 cm. Other field management practices followed conventional methods.

2.3. Measurement Indicators and Methods

2.3.1. Determination of Soil Properties

Following the sweet potato harvest in 2024, soil samples for physical structure analysis were collected using a ring knife (100 cm3). For soil chemical property analysis, soil was sampled via the five-point sampling method, then air-dried. Soil porosity, pH, and available nutrients were determined based on the method described by Bao [28]. The BD was measured by oven-drying the ring knife soil samples, and soil porosity was calculated based on BD values. Soil pH was determined using carbon dioxide-free distilled water with a soil–water ratio of 1:2.5 (w/v). The AN was determined via the alkaline hydrolysis diffusion method, AK was determined by ammonium acetate extraction, and AP was determined using the sodium bicarbonate extraction-spectrophotometric method. The determination of total soil nutrients was based on the methods of Lu [29]. The TN, TP and TK were determined by the Kjeldahl nitrogen method, the molybdenum-antimony anti-spectrophotometric method, and a hydrofluoric acid-perchloric acid mixture, respectively.

2.3.2. Yield Measurement and Sample Processing

Sweet potatoes were harvested at 150 DAT in both 2023 and 2024 for yield assessment. For each plot, the fresh mass of storage roots was weighed, and the storage root number was counted to calculate yield, number of storage roots per plant (SRN), and average weight per storage root (SRW). In 2024, a more comprehensive sampling was conducted for quality analysis. From each plot, at least three storage roots of approximately 200 g were selected, washed, dried, weighed, and diced. A portion was dried and sieved through a 0.2 mm mesh for selected nutritional quality analysis. For the subsequent determination of enzyme activities and additional nutritional quality parameters, another portion was stored at −80 °C. Additionally, some freshly washed sweet potatoes were steamed in a pot at 100 °C for 60 min, and then sampled for texture properties analysis, volatile compound determination, and sensory evaluation.

2.3.3. Determination of Nutritional Quality

The contents of total soluble sugar (TSS), sucrose, and starch were determined based on methods from Yang et al. [30] and Ambavaram et al. [31]. Briefly, dried samples were treated with 80% ethanol. The supernatants were stored for the analysis of TSS and sucrose. TSS was assayed at 620 nm using the anthrone-sulfuric acid method. Sucrose was determined at 620 nm with the same method after alkali treatment. The precipitate was reserved for starch determination, which was quantified colorimetrically at 620 nm following acid hydrolysis. Soluble protein (SP) content was measured by the Coomassie Brilliant Blue (CBB) colorimetric method [32], with absorbance measured at 595 nm. The total flavonoid (TF) and total phenolic (TP) contents were quantified according to the protocols described by Zhou et al. [33] and Shi et al. [34]. Dried samples were treated with 70% ethanol at 55 °C for 3 h. TF content was measured using the aluminum nitrate-sodium nitrite method at 510 nm, and TP content was measured via the Folin–Ciocalteu method at 765 nm. β-carotene content was determined following Zhao et al. [35], by acetone extraction and absorbance reading at 454 nm. The content of lignin was quantified using the acetyl bromide method [36,37] and measured at 280 nm.

2.3.4. Determination of Sucrose Metabolism-Related Enzyme Activities

Frozen samples were homogenized with an extraction buffer. The supernatant collected after centrifugation was kept on ice for enzyme activity assays of sucrose synthase (SS), sucrose phosphate synthase (SPS), acid invertase (AI) and neutral invertase (NI) and measured by their respective kits (Solarbio Science & Technology Co., Ltd., Beijing, China) according to the manufacturer’s instructions. The SPS and SS activities were determined using an SPS Assay Kit (BC0600–50T) and an SS Assay Kit (BC0580–50T), respectively, by measuring at 480 nm. One enzyme activity unit (U) corresponds to the amount of sucrose catalyzed per minute. The NI and AI activities were measured using an NI Assay Kit (BC0570–50T) and an AI Assay Kit (BC0560–50T), respectively, by measuring at 540 nm. One enzyme activity unit (U) corresponds to the amount of reducing sugar produced per minute.

2.3.5. Determination of Textural Properties Analysis (TPA)

According to Sanchez et al. [38] and Dong et al. [39], texture properties were determined using a TA-XT Plus texture analyzer (Stable Micro Systems Ltd., Godalming, UK). A 1 cm thick slice was taken from the central part of the steamed sweet potato storage root. Textural properties were evaluated at the center of each slice using TPA mode with a P/36R probe. The resulting curve provided parameters including hardness, springiness, cohesiveness, gumminess, and chewiness.

2.3.6. Determination of Volatile Organic Compounds (VOCs)

The VOCs were analyzed by gas chromatography–mass spectrometry (GC-MS, Agilent 7890B-5977A, Agilent Technologies, CA, USA) [40]. Freshly steamed samples were mashed, and 3 g of the mash was transferred to a 25 mL headspace vial. After adding 2-methyl-3-heptanone (1 μL, 0.163 µg µL−1) as an internal standard, it was sealed with a polytetrafluoroethylene (PTFE) septum. Then it was equilibrated at 50 °C for 30 min, and then extracted for 40 min. The extracted fiber heads were desorbed in the GC-MS inlet at 250 °C for 5 min to initiate chromatographic analysis.

2.3.7. Sensory Evaluation

A ten-member trained panel (five males and five females, aged 20–45 years) conducted the sensory evaluation. All panelists received training to enhance their sensitivity and discrimination ability for the texture and flavor attributes of sweet potato. The steamed sweet potato was prepared as 2.0 × 2.0 cm cubes for evaluation. Panelists independently scored each sample via questionnaires, using a 5-point scale where the descriptors were defined as follows: stickiness (1—not sticky, 5—sticky), aroma (1—not aromatic, 5—aromatic), fibrousness (1—high, 5—none/low), sweetness (1—not sweet, 5—sweet), and mealiness (1—not mealy, 5—mealy).

2.4. Data Processing and Mapping

The GC-MS raw data were acquired using Agilent ChemStation software (version B.04.03). Qualitative analysis was conducted using Agilent Qualitative Navigator B.08.00 software by comparing the mass spectra of individual compounds against standard mass spectral libraries such as NIST. Identification results with a match factor greater than 80% were retained. The internal standard method was used for the absolute quantification. Calculations are based on the ratio of peak areas between the target compound and the internal standard and their respective concentrations. The specific calculation formula is as follows:
C = S S i × C i m
where C denotes the target compound concentration (µg g−1); Ci denotes the internal standard concentration; S and Si denote the peak area of the target compound and the internal standard; and m denotes the mass of the sample (g).
The SPSS 26.0 software (IBM Corp., Chicago, IL, USA) was used to perform a one-way analysis of variance (ANOVA) using Tukey’s test at p < 0.05 to analyze the effect of fertilizer treatments. A two-way ANOVA was employed to assess the impacts of fertilizer treatment (F), cultivar (C), and their interactive effect (F × C) on the studied parameters. All data underwent Shapiro–Wilk tests to verify normality (p > 0.05) and Levene’s tests to assess homogeneity of variance (p > 0.05) prior to ANOVA analysis. Cluster heatmaps were constructed with TBtools v2.142 (Toolbox for Biologists, China). Other figures were generated using Origin 2025 software (OriginLab Corporation, Northampton, MA, USA).

3. Results

3.1. Effects of Different Treatments on Soil Properties

The fertilizer treatments (F) exerted a highly significant impact on soil properties (p < 0.01) (Figure 2). The OF, BOF15, and BOF30 treatments all increased soil AN, AP, AK, pH, and porosity, while significantly reducing BD (p < 0.05). The AP and AK reached their maximum values under the BOF15 treatment, significantly exceeding those under CF. Compared to CF, AP increased by 40.13% and 34.37% in YHX3 and YHX98, respectively, while AK increased by 44.80% and 45.70%, respectively. The OF, BOF15, and BOF30 treatments showed no significant differences in AN. The BD exhibited the pattern CF > OF > BOF15 > BOF30, whereas porosity showed CF < OF < BOF15 < BOF30, with significant differences among treatments. Compared to CF, BD decreased by 11.11% and 12.94% in YHX3 and YHX98, respectively, while porosity increased by 11.90% and 13.57%. Relative to all other treatments, BOF15 and BOF30 led to significantly higher pH values, which were similar to each other.

3.2. Effects of Different Treatments on Sweet Potato Yield and Its Components

Both fertilizer (F) and cultivar (C) significantly influenced storage root yield, SRW, and SRN (p < 0.01, Figure 3). The interaction between year (Y) and F was not significant (F × Y, p > 0.05), while the C × Y was significant. The storage root yield under all treatments in 2024 was overall significantly higher than that in 2023. The OF, BOF15, and BOF30 treatments significantly increased storage root yield and SRN. Only OF treatment significantly increased SRW, while BOF30 treatment significantly reduced it. Among the treatments, OF showed the best improvement in yield and SRW. Compared to CF, in 2023, the yield of YHX3 and YHX98 increased by 22.97% and 24.73%, respectively, and their SRW increased by 7.95% and 11.70%, respectively. In 2024, the yield of YHX3 and YHX98 increased by 59.82% and 27.67%, respectively, and their SRW increased by 28.47% and 8.93%, respectively. BOF30 showed the greatest enhancement effect on tuber number per plant. Compared to CF, in 2023, the tuber number per plant for YHX3 and YHX98 increased by 21.70% and 18.19%, respectively. In 2024, the increases were 24.46% for YHX3 and 17.12% for YHX98. The BOF30 treatment was most effective in increasing the SRN. Compared to CF treatment, the SRN for YHX3 and YHX98 increased by 21.70% and 18.19% in 2023, and in 2024, increased by 24.46% and 17.12%, respectively.

3.3. Effects of Different Treatments on Nutritional Quality of Sweet Potato

The OF, BOF15, and BOF30 treatments all increased the contents of primary metabolites (TSS, sucrose, starch, and SP) and secondary metabolites (TP, TF, and β-carotene) in sweet potato storage roots while reducing lignin content (Figure 4). The F, C, and F × C all reached significant levels. Compared to CF, YHX3 treated with BOF15 showed increases of 31.82%, 31.82%, 26.53%, and 38.61% in starch, TSS, sucrose, and β-carotene contents, respectively, while YHX98 showed increases of 25.98%, 28.42%, 28.48%, and 23.16%, respectively, significantly exceeding other treatments. The SP, TF, and lignin contents reached their minimum values in YHX3 under BOF30 and in YHX98 under BOF15. Compared to CF, SP content increased by 30.47% and 21.89%, TF content increased by 21.22% and 51.65%, while lignin content decreased by 19.00% and 27.78% in YHX3 and YHX98, respectively. Primary and secondary metabolites in YHX3 and YHX98 showed significant differences under different treatments. Except for starch and lignin content, all measured metabolites were significantly higher in YHX3 than in YHX98.

3.4. Effects of Different Treatments on Sucrose Metabolism-Related Enzyme Activities of Sweet Potato

The activities of sucrose metabolism-related enzymes (AI, NI, SPS, and SS) in storage roots were significantly affected by both F and C (Figure 5). The F × C reached a highly significant level for all enzymes except NI. The OF, BOF15, and BOF30 treatments significantly reduced the AI, NI, and SS activities, with AI and NI reaching minimum values under BOF15 treatment. The SS activity was lowest under the OF treatment, decreasing by 51.74% and 34.10% in YHX3 and YHX98, respectively, compared to CF. The SPS activity was significantly increased by OF, BOF15, and BOF30 treatments. Compared to CF, SPS activity increased by 53.71% and 47.92% in YHX3 and YHX98, respectively, under BOF15 treatment. The YHX3 exhibited significantly higher SS, SPS, and NI activities than YHX98.

3.5. Effects of Different Treatments on Textural Properties of Sweet Potato

TPA is a method that simulates oral food sensation and objectively measures the texture properties of food. The F, C, and F × C had highly significant effects on the texture properties, including hardness, springiness, and gumminess of sweet potato texture (Table 3). The OF, BOF15, and BOF30 treatments reduced the hardness, gumminess, and chewiness while increasing their springiness and cohesiveness. Hardness, gumminess, and chewiness reached their minimum values under the BOF30 or BOF15 treatments, while springiness reached its maximum. Compared to CF, in YHX3 under the BOF30 treatment, the hardness, gumminess, and chewiness decreased by 34.97%, 18.68%, and 9.12%, respectively, while springiness increased by 8.76%. In YHX3 under the BOF15 treatment, the hardness, gumminess, and chewiness of sweet potato texture decreased by 73.21%, 52.24%, and 23.17%, respectively, while springiness increased by 23.55%. The hardness, gumminess, and chewiness of sweet potato texture were significantly greater in YHX3 than in YHX98 across all treatments.

3.6. Effects of Different Treatments on Volatile Compounds of Sweet Potato

The GC-MS analysis identified 38 VOCs in steamed sweet potatoes under different fertilizer treatments (Figure 6). According to their chemical structures, these VOCs were classified into nine distinct chemical categories: monoterpenes (3), sesquiterpenes (17), aldehydes (6), alcohols (4), ketones (2), benzene derivatives (2), esters (2), acids (1), and alkanes (1). Among them, terpenes (monoterpenes and sesquiterpenes) and aldehydes exhibited higher proportions and diversity in VOCs across all treatments (Figure 6A). Terpene content ranged from 68.63% to 87.02% in YHX3 and from 21.84% to 57.32% in YHX98, while aldehyde content ranged from 7.74% to 23.81% in YHX3 and from 30.44% to 54.14% in YHX98. Principal Component Analysis (PCA) explained 54.8% of the total variance (PC1 37.9%, PC2 16.9%) and showed clear separation (Figure 6B), which indicated certain differences in VOCs among different treatments. Consequently, a heatmap of VOC content (Figure 6C) and ANOVA (Table 4) was conducted. The OF, BOF15, and BOF30 treatments increased the diversity of VOCs and the content of specific terpenes and aldehydes, including β-cyclocitral, β-caryophyllene, α-humulene, and phenylacetaldehyde in both YHX3 and YHX98. Except for β-cyclocitral, these compounds reached their maximum levels under the BOF15 treatment.
Additionally, YHX3 and YHX98 exhibited 31 and 25 VOCs, respectively, with 18 VOCs common to both cultivars. Most terpenes, aldehydes, ketones, and benzene derivatives, such as linalool, β-cyclocitral, β-ionone, 2,2,6-trimethylcyclohexanone, and α-lonene, had higher concentrations in YHX3 than in YHX98.

3.7. Effects of Different Treatments on Sensory Evaluation of Sweet Potato

By measuring the sensory characteristics in steamed storage roots, the effects of fertilizer treatments on flavor were evaluated. Figure 7 shows the distribution of sensory evaluation scores for YHX3 and YHX98 under four different fertilizer treatments. Under the CF treatment, both cultivars exhibited lower stickiness, mealiness, aroma, and sweetness scores compared to other treatments. The YHX3 scored highest in mealiness, aroma, and fibrousness under the BOF15 treatment, followed by BOF30. The YHX98 scored higher than YHX3 in all categories. For YHX98, the highest scores for stickiness, mealiness, aroma, and sweetness were achieved under the BOF15 treatment, followed by the BOF30 and OF treatments. YHX98 consistently scored higher than YHX3.

3.8. Correlation Analysis Between Soil Properties and the Yield and Quality of Sweet Potato

Correlation analysis was employed to explore the associations of storage root yield and quality (nutritional and flavor) with soil properties (Figure 8). The results indicated that, for both cultivars, soil pH, AN, AP, AK, and porosity were positively correlated with storage root yield, SRN, key nutritional quality components (starch, TSS, sucrose, SP, and β-carotene), and SPS activity. Conversely, lignin content and the NI, AI, and SS activities showed a negative correlation with them. This suggests that appropriate soil fertility and physical structure can influence sucrose metabolism and the biosynthesis of cell wall components (e.g., lignin), thereby promoting yield improvement and nutrient accumulation in sweet potatoes. Further analysis revealed that key nutritional quality components showed positive correlations with texture properties (springiness, cohesiveness) and certain VOCs (sesquiterpenes, alcohols), while negatively correlated with texture properties (hardness, gumminess, and chewiness) and the content of certain VOCs (aldehydes, benzene derivatives). Lignin content showed opposite correlations with these indicators. This indicates that the sweet potato texture and flavor qualities are regulated by the accumulation of carbohydrate metabolites.

4. Discussion

4.1. Synergistic Effects of Biochar-Based Organic Fertilizer on Soil Properties and Sweet Potato Yield

Biochar can enhance soil nutrient availability and structure, and create a more favorable environment for plants [45]. In this study, the OF, BOF15, and BOF30 treatments significantly increased soil nutrient availability, pH, and porosity while reducing BD. Among these, the combined application showed the most pronounced improvement (Figure 2), consistent with previous studies [46,47]. The observed rise in soil pH following application of biochar-based organic fertilizer is primarily attributed to the alkalinity of biochar. Previous research indicated that alkaline biochar can release substantial cations into the soil, reducing soil acidity through proton-consuming reactions. Simultaneously, its surface contains reactive pH-dependent functional groups that can elevate pH levels [48,49].
The organic fertilizer can enhance the mineralization and renewal of native soil organic matter, increasing organic matter content, facilitating the aggregation of loose soil particles into stable aggregates, which can improve soil physical structure and promote nutrient release [27]. Concurrently, biochar can effectively adsorb soil nutrients while improving soil structure, thereby enhancing nutrient retention, reducing leaching losses, and slowing the decomposition of organic fertilizer [50,51]. The combined application of both can sustain the equilibrium between soil nutrient supply and plant demand [52], which is beneficial for increasing sweet potato yield (Figure 3). Correlation results further indicate that sweet potato yield is highly correlated with soil properties (Figure 8). The results imply that an appropriate combination of biochar and organic fertilizer may optimize sweet potato root architecture and hormone signaling by regulating soil pH, nutrient availability, and soil aeration. This likely promotes the allocation of carbon assimilates towards sucrose synthesis in the storage roots, ultimately increasing sweet potato yield [53,54]. Meanwhile, biochar-based organic fertilizer may also indirectly modulate nutrient cycling and phytohormone environments by altering the rhizosphere environment [55].
Notably, the yield under the high biochar ratio treatment (BOF30) did not increase and even slightly decreased compared to the OF treatment (Figure 3A), while soil available nutrients under BOF30 were lower than under BOF15 (Figure 2). This suggests that when the biochar proportion exceeds 30%, its excessively strong adsorption may inhibit nutrient availability. In addition, the persistent rise in soil pH may exceed the optimal range for sweet potato growth, thereby affecting root nutrient uptake or soil microbial symbiosis, ultimately leading to a decline in yield. It should be noted that the overall sweet potato yield in 2024 was significantly lower than that in 2023, which may be associated with unfavorable climatic conditions (e.g., high temperature and drought) encountered during that growing season. However, under these relatively unfavorable conditions, the biochar-based organic fertilizer treatments still maintained a significant yield-increasing effect compared to the CF treatment. This further highlights the robustness and application potential of these formulations.

4.2. Regulation of Sweet Potato Nutritional Quality by Biochar-Based Organic Fertilizer

Biochar application can improve crop quality and increase soluble solid content [27,56]. This study similarly found that organic and biochar-based organic fertilizer exerted positive effects on the nutritional quality of sweet potato, including primary metabolites (TSS, sucrose, starch, and SP) and secondary metabolites (TP, TF, β-carotene, and lignin) (Figure 4). Among them, the BOF15 treatment showed the most significant improvement effect on TSS, sucrose, starch, and β-carotene, possibly due to the most suitable soil environment under this treatment. SS, SPS, AI, and NI are key enzymes in sucrose metabolism, playing crucial regulatory roles in quality formation. SS catalyzes the reversible reaction between sucrose synthesis and breakdown, SPS influences the allocation of photosynthetic products between sucrose and starch, while AI and NI irreversibly hydrolyze sucrose into fructose and glucose [57,58]. This study indicates that OF, BOF15, and BOF30 treatments can reduce AI, NI, and SS activities while increasing SPS activity, thereby regulating sugar metabolism and promoting sucrose accumulation [59]. Furthermore, in storage organs, there exists an intrinsic trade-off in carbon allocation between the synthesis of TSS and starch on one hand, and structural components like cell wall lignin on the other [60]. The excessive accumulation of lignin can reduce sugar content, which consequently impedes starch synthesis and restricts cell expansion [61]. In this study, the observed decrease in lignin content, accompanied by the increased starch and sugar content under biochar-based organic fertilizer treatments, precisely reflects this shift in carbon allocation priority. In addition, correlation analysis revealed a potential relationship between the synergistic changes in soil properties and sweet potato quality (Figure 8).
These results indicate that the application of biochar can improve soil structure and regulate nutrient supply through adsorption, slow-release, or pH adjustment, thereby providing a more sustained and balanced nutritional foundation for storage root development, which supports the accumulation of higher levels of metabolic products. Under such more favorable growth conditions, sweet potatoes up-regulate key sucrose metabolism enzyme activities and alter carbon allocation, directing more photosynthetic products toward the synthesis of sucrose and starch in the tubers rather than toward lignification of cell walls. Ultimately, this enhances the content of compounds such as sugars, starch, and β-carotene, which determine nutritional quality.

4.3. Optimization of Sweet Potato Flavor and Texture by Biochar-Based Organic Fertilizer

Texture significantly impacts food mouthfeel [62]. In this study, both organic fertilizer and biochar-based organic fertilizer applications reduced hardness, gumminess, and chewiness of storage roots while increasing springiness and cohesiveness. They also improved sensory evaluation scores, with the best effect observed in the BOF15 treatment. This improvement may be closely linked to its regulatory effects on carbohydrate metabolism. Specifically, a decreased lignin content contributes to reduced cell wall rigidity, while an elevated sugar level primarily enhances cellular turgor pressure. These changes collectively influence cell wall structure and composition, thereby regulating textural properties [63]. Correlation results further support the intrinsic relationship between carbohydrates and texture (Figure 8). Furthermore, YHX3 exhibited significantly higher hardness, gumminess, and chewiness than YHX98. This disparity could be due to inter-cultivar differences in the composition of buffering substances such as cellulose, sugars, and pectin [64].
The contribution of VOCs to flavor is primarily determined by their relative abundance and their ratio to their respective odor thresholds [65,66]. Aldehydes, with their characteristically low odor thresholds, are pivotal to the development of aroma, imparting fatty and grassy notes (Table 4). Terpenes contribute sweetness and woody aromas, while alcohols primarily serve to complement and round out the main fragrance profile. Ketones, though present in smaller quantities and offering creamy and fruity notes, contribute less significantly to the overall flavor. This study found that the OF, BOF15, and BOF30 treatments increased both the diversity of VOCs and the content of specific terpenes and aldehydes, thereby enhancing the sweet and grassy aroma profiles of sweet potato (Figure 6). Sweetness is a key factor in consumers’ perceived quality, and its enhancement can increase people’s preference for sweet potatoes and boost market consumption [63].
The VOCs identified in this study were predominantly aldehydes and terpenes, which exhibited greater diversity and higher concentrations. The composition and concentration of VOCs depend on the intrinsic nutrients in the plant, such as carbohydrates and free amino acids, which undergo cleavage or polymerization during heating to transform into various flavor compounds [5]. Terpene synthesis is related to the decomposition of TSS and carotenoids, both serving as precursor materials. They can generate monoterpenes and sesquiterpenes through oxidative cleavage, collectively contributing to the sweetness and floral aroma of sweet potato [67]. Aldehydes, originating mainly from the breakdown of amino acids and fatty acids, provide fatty and grassy notes [68]. The TSS content, which directly affects both sweetness and texture, is determined by the extent of starch saccharification during the heating process [63,69]. These indicate that biochar-based organic fertilizer increased the content of precursor substances such as starch, TSS, SP, and β-carotene. This created a richer substrate pool for generating a greater diversity and higher content of VOCs (e.g., aldehydes, terpenes) via degradation processes during steaming, ultimately improving the flavor quality of sweet potato. Among the treatments, BOF15 demonstrated the most effective enhancement of aldehydes, terpenes, and other VOCs, resulting in the best improvement in flavor quality.
Within the context of the particular soil and climatic conditions in this study, the BOF15 treatment (biochar-based organic fertilizer containing 15% biochar) demonstrated the best overall performance in synergistically improving soil, enhancing yield, and optimizing comprehensive quality. Therefore, it is advisable that producers, particularly in regions with soils poor in organic matter or unfavorable structure, consider applying biochar-based organic fertilizer as a partial substitute for or supplement to conventional mineral fertilizers. This practice holds promise for improving the marketable quality of storage roots while gradually enhancing the soil’s capacity to retain water and nutrients.

5. Conclusions

This study investigated the impacts of applying organic fertilizer and biochar in combination on soil properties, sweet potato yield, and quality. The findings revealed that organic fertilizer alone and its combination with biochar significantly improved soil structure and enhanced the content of soil available nutrients. Meanwhile, they could promote the production and accumulation of TSS and sucrose by regulating sucrose metabolism enzyme activities. This maintained a dynamic balance between the synthesis of sugars and lignin, ultimately improving sweet potato yield and nutritional quality. Furthermore, changes in lignin, sugar, and starch content regulated cell wall structure and increased the diversity and content of key VOCs such as terpenes and aldehydes in steamed storage roots. This improved the textural properties and flavor quality, elevating the overall eating quality of the sweet potato. In summary, the biochar-based organic fertilizer containing 15% biochar (BOF15) represents the optimal strategy for achieving soil improvement, yield increase, and synergistic enhancement of comprehensive quality.
The experiment was conducted with only two sweet potato cultivars, under a specific location. This may limit the generalizability of the results across different climatic years, soil types, or geographic regions. Future research involving multi-year trials and multi-location field experiments is needed to validate the long-term stability and broader applicability of the effects.

Author Contributions

Conceptualization, G.S.; methodology, Z.D.; formal analysis, Y.L., Y.S., and S.D.; investigation, R.Z., F.Z., and T.W.; writing—original draft preparation, G.S.; writing—review and editing, G.S. and J.W.; project administration, K.D., C.L., and D.T.; funding acquisition, J.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Seed Industry “Potato Science and Enterprise Consortium Special Program” of the Chongqing Agriculture and Rural Affairs Commission (2021–2025), the Special Program for Potato Innovation Team of the Chongqing Modern Agricultural Industrial Technology System (CQMAITS2023-4), and the Shuangcheng Cooperative Agreement Research Grant of Yibin (YBSCXY2023020013).

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Temperature and precipitation conditions during the experiment.
Figure 1. Temperature and precipitation conditions during the experiment.
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Figure 2. Soil properties under different treatments. (A) Alkali-hydrolyzable nitrogen (AN) content; (B) available phosphorus (AP) content; (C) available potassium (AK) content; (D) pH; (E) soil porosity; (F) soil bulk density (BD). CF, inorganic compound fertilizer only; OF, 2337.55 kg·ha−1 organic fertilizer (replacing 30% inorganic N) combined with inorganic fertilizer; BOF15, 2337.55 kg·ha−1 biochar-based organic fertilizer (containing 15% biochar) combined with inorganic fertilizer; BOF30, 2337.55 kg·ha−1 biochar-based organic fertilizer (containing 30% biochar) combined with inorganic fertilizer. YHX3, Yuhongxinshu3; YHX98, Yuhongxinshu98. Different lowercase letters denote significant differences among fertilizer treatments (p < 0.05). ** denotes significant correlations at the 0.01 level. “ns” denotes non-significance (p > 0.05).
Figure 2. Soil properties under different treatments. (A) Alkali-hydrolyzable nitrogen (AN) content; (B) available phosphorus (AP) content; (C) available potassium (AK) content; (D) pH; (E) soil porosity; (F) soil bulk density (BD). CF, inorganic compound fertilizer only; OF, 2337.55 kg·ha−1 organic fertilizer (replacing 30% inorganic N) combined with inorganic fertilizer; BOF15, 2337.55 kg·ha−1 biochar-based organic fertilizer (containing 15% biochar) combined with inorganic fertilizer; BOF30, 2337.55 kg·ha−1 biochar-based organic fertilizer (containing 30% biochar) combined with inorganic fertilizer. YHX3, Yuhongxinshu3; YHX98, Yuhongxinshu98. Different lowercase letters denote significant differences among fertilizer treatments (p < 0.05). ** denotes significant correlations at the 0.01 level. “ns” denotes non-significance (p > 0.05).
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Figure 3. Sweet potato yield and yield components under different treatments. (A) Storage root yield; (B) number of storage roots per plant (SRN); (C) average weight per storage root (SRW). Different lowercase letters denote significant differences among fertilizer treatments (p < 0.05). ** and * denote significant correlations at the 0.01 and 0.05 levels, respectively. “ns” denotes non-significance (p > 0.05).
Figure 3. Sweet potato yield and yield components under different treatments. (A) Storage root yield; (B) number of storage roots per plant (SRN); (C) average weight per storage root (SRW). Different lowercase letters denote significant differences among fertilizer treatments (p < 0.05). ** and * denote significant correlations at the 0.01 and 0.05 levels, respectively. “ns” denotes non-significance (p > 0.05).
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Figure 4. Nutritional quality of sweet potato under different treatments. (A) Total soluble sugar (TSS) content; (B) sucrose content; (C) starch content; (D) soluble protein (SP) content; (E) total phenolic (TP) content; (F) total flavonoid (TF) content; (G) β-carotene content; (H) lignin content. Different lowercase letters denote significant differences among fertilizer treatments (p < 0.05). ** and * denote significant correlations at the 0.01 and 0.05 levels, respectively.
Figure 4. Nutritional quality of sweet potato under different treatments. (A) Total soluble sugar (TSS) content; (B) sucrose content; (C) starch content; (D) soluble protein (SP) content; (E) total phenolic (TP) content; (F) total flavonoid (TF) content; (G) β-carotene content; (H) lignin content. Different lowercase letters denote significant differences among fertilizer treatments (p < 0.05). ** and * denote significant correlations at the 0.01 and 0.05 levels, respectively.
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Figure 5. Sucrose metabolism-related enzyme activities of sweet potato under different treatments. (A) Neutral invertase (NI) activity; (B) acid invertase (AI) activity; (C) sucrose synthase (SS) activity; (D) sucrose phosphate synthase (SPS) activity. Different lowercase letters denote significant differences among fertilizer treatments (p < 0.05). ** denotes significant correlations at the 0.01 level. “ns” denotes non-significance (p > 0.05).
Figure 5. Sucrose metabolism-related enzyme activities of sweet potato under different treatments. (A) Neutral invertase (NI) activity; (B) acid invertase (AI) activity; (C) sucrose synthase (SS) activity; (D) sucrose phosphate synthase (SPS) activity. Different lowercase letters denote significant differences among fertilizer treatments (p < 0.05). ** denotes significant correlations at the 0.01 level. “ns” denotes non-significance (p > 0.05).
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Figure 6. Volatile organic compounds (VOCs) in storage roots of sweet potato under different treatments. (A) Category statistics of VOCs in each treatment; (B) principal component analysis (PCA) of VOCs; (C) heat map of VOCs abundance. In the heatmap, red and blue blocks denote up- and down-regulated metabolites relative to the mean (white).
Figure 6. Volatile organic compounds (VOCs) in storage roots of sweet potato under different treatments. (A) Category statistics of VOCs in each treatment; (B) principal component analysis (PCA) of VOCs; (C) heat map of VOCs abundance. In the heatmap, red and blue blocks denote up- and down-regulated metabolites relative to the mean (white).
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Figure 7. Sensory evaluation of sweet potato under different treatments. (A) YHX3; (B) YHX98.
Figure 7. Sensory evaluation of sweet potato under different treatments. (A) YHX3; (B) YHX98.
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Figure 8. Correlation between soil properties and sweet potato yield and quality under different treatments. (A) YHX3; (B) YHX98. SRN, number of storage roots per plant; SRW, average weight per storage root; TSS, total soluble sugars; SP, soluble protein; TP, total phenols; TF, total flavonoids. ** and * denote significant correlations at the 0.01 and 0.05 levels, respectively.
Figure 8. Correlation between soil properties and sweet potato yield and quality under different treatments. (A) YHX3; (B) YHX98. SRN, number of storage roots per plant; SRW, average weight per storage root; TSS, total soluble sugars; SP, soluble protein; TP, total phenols; TF, total flavonoids. ** and * denote significant correlations at the 0.01 and 0.05 levels, respectively.
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Table 1. Fertilizer application rates of each treatment.
Table 1. Fertilizer application rates of each treatment.
TreatmentInorganic Fertilizer Application (kg·ha−1)Organic Fertilizer
+Biochar (kg·ha−1)		Total Nutrients (kg·ha−1)
Compound FertilizerNitrogen FertilizerPotassium FertilizerNP2O5K2O
CF1071.380.000.000171.4253.57224.99
OF370.11132.12260.692337.55 + 0171.4253.57224.99
BOF15557.1280.80190.742206.73 + 389.42171.4253.57224.99
BOF30650.6275.21155.111817.30 + 778.85171.4253.57224.99
Table 2. The chemical properties of fertilizers.
Table 2. The chemical properties of fertilizers.
IndicatorsOrganic FertilizerBiocharBiochar-Based Organic Fertilizer
Containing 15% BiocharContaining 30% Biochar
pH (H2O)7.319.207.597.88
TN (g·kg−1)22.000.1219.3014.00
TP (g·kg−1)6.550.014.803.93
TK (g·kg−1)2.490.051.911.74
Table 3. Textural properties of sweet potato under different treatments.
Table 3. Textural properties of sweet potato under different treatments.
CultivarFertilizerHardness (N) SpringinessCohesivenessGumminess (N)Chewiness (N)
YHX3CF12.39 ± 0.25 a0.73 ± 0.01 c0.44 ± 0.01 c5.39 ± 0.13 a3.94 ± 0.08 a
OF10.70 ± 0.25 b0.75 ± 0.00 bc0.46 ± 0.01 b4.95 ± 0.02 b3.70 ± 0.04 b
BOF159.31 ± 0.33 c0.77 ± 0.02 ab0.51 ± 0.02 a4.76 ± 0.13 bc3.64 ± 0.12 b
BOF309.18 ± 0.17 c0.79 ± 0.01 a0.50 ± 0.01 a4.54 ± 0.16 c3.61 ± 0.14 b
YHX98CF10.95 ± 0.35 a0.65 ± 0.01 c0.44 ± 0.02 c4.82 ± 0.07 a3.11 ± 0.09 a
OF8.20 ± 0.33 b0.72 ± 0.00 b0.47 ± 0.01 bc3.83 ± 0.10 b2.77 ± 0.07 b
BOF156.32 ± 0.38 d0.80 ± 0.01 a0.50 ± 0.01 ab3.17 ± 0.24 c2.53 ± 0.22 b
BOF307.16 ± 0.16 c0.77 ± 0.02 a0.51 ± 0.02 a3.67 ± 0.04 b2.81 ± 0.11 ab
Significance
Fertilizer (F)**********
Cultivar (C)****ns****
F × C****ns**ns
Note: Data are expressed as mean ± standard deviation (n = 3). Within the same cultivar, significant differences (p < 0.05) between fertilizer treatments are indicated by different lowercase letters. ** indicates significant correlations at 0.01. “ns” denotes not significant (p > 0.05).
Table 4. The VOC content and levels in sweet potato under different treatments.
Table 4. The VOC content and levels in sweet potato under different treatments.
No.CompoundCASYHX3 (μg·kg−1)YHX98 (μg·kg−1)Threshold
(μg·kg−1) ①		Description ②
CFOFBOF15BOF30CFOFBOF15BOF30
1Linalool78-70-617.11 ± 1.34 a13.95 ± 1.07 b5.58 ± 1.27 d8.48 ± 1.28 c3.07 ± 0.79 b3.71 ± 0.20 ab4.93 ± 0.91 a3.14 ± 0.41 b1.5flower, lavender
2α-Terpineol98-55-5n.d.2.41 ± 0.31 an.d.n.d.n.d.n.d.n.d.n.d.0.3oil, anise, mint
3β-Cyclocitral432-25-75.18 ± 0.94 b8.65 ± 0.77 a7.78 ± 1.04 a5.81 ± 0.56 bn.d.2.15 ± 0.21 b2.98 ± 0.40 a2.03 ± 0.34 b0.15mint
4α-Neocaryophyllene4545-68-0n.d.n.d.n.d.n.d.n.d.17.65 ± 0.46 an.d.n.d.n.d.wood, dry, amber
5β-Caryophyllene469-92-178.29 ± 9.84 b125.79 ± 8.39 a120.80 ± 22.08 a50.91 ± 11.95 b10.17 ± 0.52 d12.50 ± 0.29 c16.37 ± 0.42 a14.29 ± 0.53 b0.16wood, spice
6Isocaryophyllene118-65-08.57 ± 2.50 a5.68 ± 1.10 an.d.n.d.2.11 ± 0.52 bn.d.4.03 ± 0.75 an.d.n.d.wood
7α-Humulene6753-98-616.30 ± 1.74 c25.58 ± 1.82 b36.64 ± 2.20 a11.53 ± 0.79 dn.d.n.d.5.95 ± 1.38 an.d.0.16wood
8α-Copaene3856-25-56.48 ± 2.12 b8.58 ± 0.92 ab11.02 ± 1.50 an.d.n.d.n.d.n.d.n.d.n.d.wood, spice
9β-Elemene515-13-94.69 ± 4.69 an.d.n.d.n.d.n.d.n.d.n.d.n.d.0.46herb, wax, fresh
10Calarene17334-55-3n.d.n.d.n.d.3.66 ± 0.15 an.d.n.d.n.d.n.d.n.d.wood, sweet
11δ-Elemol20307-84-025.46 ± 6.08 a17.68 ± 2.95 ab17.37 ± 7.34 ab8.54 ± 1.65 bn.d.n.d.5.48 ± 1.41 an.d.n.d.green, wood
12α-Guaiene3691-12-1n.d.14.01 ± 0.81 b22.88 ± 0.52 a12.00 ± 0.30 cn.d.n.d.n.d.n.d.0.12wood, balsamic
13γ-Elemene29873-99-27.62 ± 0.35 d12.79 ± 0.66 b15.97 ± 0.89 a10.84 ± 0.45 cn.d.n.d.n.d.n.d.n.d.green, wood, oil
14Rotundene65128-08-7n.d.n.d.n.d.n.d.4.35 ± 0.10 ab3.20 ± 0.31 b5.50 ± 0.47 a3.22 ± 0.87 bn.d.wood, sweet
15Helminthogermacrene75023-40-4n.d.n.d.2.46 ± 1.04 b4.70 ± 0.36 an.d.5.52 ± 1.46 a2.28 ± 0.99 bn.d.n.d.n.d.
16Calamecene483-77-210.67 ± 2.38 a8.59 ± 1.23 an.d.3.89 ± 1.50 bn.d.5.43 ± 1.05 an.d.4.21 ± 1.01 an.d.herb, spice
17Guaia-6,9-diene36577-33-0n.d.11.06 ± 1.50 an.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.
18Guaiazulene489-84-922.70 ± 5.23 b34.31 ± 2.80 a24.16 ± 1.58 b12.27 ± 1.40 c4.31 ± 1.11 an.d.n.d.n.d.n.d.herbal, spice, wood
19Germacrene D23986-74-5n.d.n.d.n.d.4.01 ± 4.01 an.d.n.d.n.d.n.d.n.d.wood, spice
20Cadalene483-78-32.35 ± 0.53 b2.14 ± 0.67 b4.90 ± 0.89 an.d.1.05 ± 0.20 c1.94 ± 0.42 b5.45 ± 0.38 a2.29 ± 0.39 bn.d.herbal, spice, wood
21β-Homocyclocitral472-66-24.84 ± 0.40 a3.65 ± 0.36 b2.32 ± 0.28 c2.46 ± 0.51 cn.d.n.d.n.d.n.d.n.d.wood, sweet, fruity, floral
22Benzaldehyde100-52-7n.d.28.16 ± 6.01 an.d.24.71 ± 2.61 a39.11 ± 7.97 a46.28 ± 7.56 an.d.25.55 ± 4.76 b1.5almond, burnt sugar
23Phenylacetaldehyde122-78-17.61 ± 0.59 c9.84 ± 0.56 b12.84 ± 0.58 a11.95 ± 0.93 a11.10 ± 0.44 c13.22 ± 0.64 b16.53 ± 1.24 a12.99 ± 0.56 b4.0berry, geranium, honey
24Decanal112-31-220.82 ± 1.39 a12.50 ± 0.84 b8.82 ± 1.40 c8.29 ± 1.69 c11.96 ± 0.73 a7.07 ± 0.59 bc8.57 ± 0.59 b6.12 ± 0.80 c7.0soap, orange peel, tallow
25Nonanal124-19-6n.d.n.d.n.d.n.d.n.d.n.d.3.04 ± 0.88 an.d.1.0fat, citrus, green
26(E)-2-Nonenal18829-56-62.29 ± 0.91 an.d.n.d.n.d.n.d.n.d.n.d.n.d.0.4cucumber, fat, green
271,14-Tetradecanediol19812-64-7n.d.1.40 ± 0.19 an.d.n.d.n.d.0.62 ± 0.02 an.d.n.d.n.d.n.d.
281-Octanol111-87-5n.d.n.d.n.d.n.d.n.d.n.d.5.91 ± 1.04 an.d.0.9chemical, metal, burnt
291-Undecanol112-42-5n.d.n.d.1.42 ± 1.42 an.d.n.d.n.d.2.52 ± 2.52 an.d.0.5mandarin
303,5-Dimethylcyclohexanol5441-52-1n.d.n.d.2.54 ± 0.70 an.d.n.d.n.d.n.d.n.d.1.5n.d.
312,2,6-Trimethylcyclohexanone2408-37-95.76 ± 0.49 a3.81 ± 0.45 b2.04 ± 0.30 c3.20 ± 0.57 b2.17 ± 0.24 a1.98 ± 0.11 ab1.72 ± 0.06 b1.57 ± 0.04 cn.d.floral
32β-Ionone79-77-617.05 ± 1.10 a13.29 ± 0.62 b8.43 ± 2.41 c8.71 ± 1.66 cn.d.5.30 ± 0.57 bn.d.7.05 ± 0.43 a0.01seaweed, violet, flower
33α-Lonene475-03-62.55 ± 0.94 a3.08 ± 1.22 a1.81 ± 0.98 a3.14 ± 1.37 a1.74 ± 0.52 a1.73 ± 0.19 a1.16 ± 0.19 a2.27 ± 0.72 a0.1Fruit
342,4′,6-Trimethyl-1,1′-biphenyl76708-76-45.39 ± 0.26 a5.88 ± 1.27 an.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.
35Mono(2-ethylhexyl) adipate4337-65-92.06 ± 0.13 an.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.
36Dihydroactinidiolide17092-92-1n.d.n.d.n.d.n.d.7.22 ± 0.46 an.d.n.d.n.d.0.5fruity, wood, sweet
37Dodecanoic acid143-07-7n.d.n.d.n.d.n.d.16.46 ± 1.79 an.d.n.d.n.d.0.5metal
382-Methylbutylcyclopentane53366-38-4n.d.n.d.n.d.n.d.n.d.1.09 ± 0.53 an.d.n.d.n.d.n.d.
Notes: Within the same cultivar, significant differences (p < 0.05) between fertilizer treatments are indicated by different lowercase letters. “n.d.” indicates not detected. ①: The odor characteristics and thresholds of compounds in water referenced from the literature [41,42,43,44]. ②: Data sourced from the Flavornet database: https://www.flavornet.org/flavornet.html (accessed on 27 January 2026).
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Sun, G.; Deng, Z.; Zhao, R.; Zhao, F.; Wang, T.; Li, Y.; Song, Y.; Deng, S.; Du, K.; Lyu, C.; et al. Effects of Biochar Combined with Organic Fertilizer on Soil Properties and the Yield and Quality of Sweet Potato. Horticulturae 2026, 12, 235. https://doi.org/10.3390/horticulturae12020235

AMA Style

Sun G, Deng Z, Zhao R, Zhao F, Wang T, Li Y, Song Y, Deng S, Du K, Lyu C, et al. Effects of Biochar Combined with Organic Fertilizer on Soil Properties and the Yield and Quality of Sweet Potato. Horticulturae. 2026; 12(2):235. https://doi.org/10.3390/horticulturae12020235

Chicago/Turabian Style

Sun, Guangyan, Zhenpeng Deng, Ruina Zhao, Fangxi Zhao, Tenglong Wang, Yucui Li, Yiming Song, Shuwen Deng, Kang Du, Changwen Lyu, and et al. 2026. "Effects of Biochar Combined with Organic Fertilizer on Soil Properties and the Yield and Quality of Sweet Potato" Horticulturae 12, no. 2: 235. https://doi.org/10.3390/horticulturae12020235

APA Style

Sun, G., Deng, Z., Zhao, R., Zhao, F., Wang, T., Li, Y., Song, Y., Deng, S., Du, K., Lyu, C., Tang, D., & Wang, J. (2026). Effects of Biochar Combined with Organic Fertilizer on Soil Properties and the Yield and Quality of Sweet Potato. Horticulturae, 12(2), 235. https://doi.org/10.3390/horticulturae12020235

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