Influence of soil health on tomato sensory quality: a PRISMA-based systematic review

Abstract

Tomatoes (Solanum lycopersicum) are globally prized for their sensory qualities, including flavour, aroma, texture, and appearance, which shape consumer preference and marketability. This systematic review explores the influence of soil health on these attributes, focusing on nutrient composition, microbial activity, and management practices. Following PRISMA guidelines, 598 records from three databases were initially identified: Scopus (43), PubMed (18), and Taylor & Francis (537). After duplicate removal and successive screening steps; title, abstract, and full-text review, a total of twelve (12) studies met the inclusion criteria and were retained for the final analysis. All twelve studies (100%) assessed flavour, ten (10) analyzed appearance, while aroma and texture were each evaluated in six (6) studies. Nine (9) of the papers reveal that balanced macronutrients (nitrogen, phosphorus, potassium) and soil amendments like biochar and organic fertilizers significantly enhance tomato sensory profiles by optimizing sugar-acid balance, aroma compound synthesis, and fruit firmness. Seven (7) studies found that sustainable practices, including reduced synthetic fertilizer use and improved microbial diversity, were shown to mitigate soil degradation while boosting nutrient cycling and water retention. Conversely, four papers found that soil contamination with heavy metals and poor management practices were linked to diminished sensory quality, including off-flavors and reduced sweetness. Soil health strongly affects tomato sensory quality. Organic amendments such as biochar and compost substantially enhance flavour, aroma, texture, and visual appeal. Integrated soil management strategies and farmer training are recommended. Future research should quantify long-term effects and explore links between sensory quality and nutritional outcomes.

Introduction

Tomato (Solanum lycopersicum) is one of the most widely cultivated and economically important crops in the world and also holds significant value for its sensory qualities, such as flavour, aroma, texture, and appearance [1, 2, 3]. These characteristics are critical for consumer preference and are essential for the tomato’s role in food products, from fresh consumption to processed goods like sauces, pastes, and juices. As climate change continues to reshape agricultural practices and environmental conditions, and as soil health declines due to intensive farming practices, the sensory quality of tomatoes may be increasingly impacted.

Soil health significantly influences tomato quality by affecting nutrient availability, water retention, and microbial activity, all of which impact flavour and texture [4]. Healthy soils enriched with organic matter and beneficial microorganisms foster efficient nutrient cycling, enhancing the nutrient composition and sensory profile of tomatoes [5]. On the other hand, poor soil management practices, such as over-reliance on synthetic fertilizers and soil compaction, disrupt the nutrient balance, reduce biodiversity, and compromise quality. Key nutrient imbalances, particularly in nitrogen, potassium, and magnesium, can lead to off-flavours, reduced sweetness, and undesirable texture changes [6].

Unsustainable agricultural practices, including monocropping, synthetic fertilizer overuse, and inadequate soil management, have been identified as major contributors to soil health degradation. This deterioration negatively affects nutrient cycling, microbial activity, and water retention, which are the key factors shaping the attributes of tomatoes, such as flavour, aroma, texture, and appearance. Studies highlight that imbalanced nutrient profiles and reduced soil biodiversity are often linked to adverse changes in sensory qualities, including diminished sweetness and undesirable off-flavors, thereby compromising the market value and consumer acceptability of tomatoes.

Although sustainable agricultural practices are gaining recognition, a comprehensive understanding of the relationship between soil health and tomato sensory quality remains lacking. Addressing this gap forms the basis for the objectives of this systematic review. The study aims to systematically review the impacts of soil health on the quality of tomatoes. It seeks to evaluate how soil nutrient composition influences sensory attributes such as flavour, aroma, texture, and appearance. The study also examines the effects of various soil management practices, including organic amendments, crop rotation, and reduced synthetic fertilizer use, on the sensory quality of tomatoes. The review analyzes the role of soil microbial activity and biodiversity in shaping the characteristics of tomatoes. The findings aim to support evidence-based strategies for sustainable soil management, promoting improved tomato sensory attributes, enhancing consumer satisfaction, and bolstering agricultural productivity.

This review seeks to investigate the influence of soil health on the sensory quality of tomatoes by addressing several key questions: How do different soil health parameters, such as nutrient content, pH, organic matter, and contamination levels, affect the flavour, aroma, texture, and appearance of tomato fruits? What is the impact of specific soil amendments, including biochar, biogas slurry, and mineral fertilizers, on tomato growth, yield, and sensory attributes?

Materials and methods

Research design

The review adhered to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, ensuring a rigorous and transparent process for searching, selecting, and synthesizing the literature. The study adopted a systematic approach to examine the relationship between soil health and tomato sensory qualities. A robust framework was employed to identify and analyze over 500 relevant studies extracted from three scientific databases. Clear inclusion and exclusion criteria were developed to ensure the selection of studies aligned with the research objectives. Data extraction and thematic analysis techniques were utilized to identify recurring themes and trends within the selected studies.

Data sources and search strategy

The search strategy for this review involved comprehensive database searches, including PubMed, Scopus, and Taylor and Francis. The key search terms were “effects,” “soil health,” “sensory quality,” and “tomatoes.” For soil health, terms like “soil nutrients,” “organic matter”, “soil composition,” and “pesticide residues” were included, and “colour”, “flavour”, “aroma,” and “taste” represented sensory quality.

Truncations and wildcards were included in the search to maximize the retrieval of relevant literature. Truncations such as “nutrient*,” “composit*,” “residu*,” “pattern*,” “qualit*,” and “tomato*” were used to capture variations of these terms. Wildcards, like the asterisk (*), were employed to broaden the search scope by finding all possible word endings.

Boolean operators (AND, OR) were used to refine the search, and truncation and wildcards were employed to capture variations in word forms. The search string below was used to maximize the retrieval of relevant literature: (“Impact” OR “Effects” OR “Results” OR “Consequence” OR “Outcome” OR “Contribution”) AND (“Soil health” OR “Soil quality” OR “Soil nutrient” OR “Soil pH” OR “Soil structure” OR “Soil contaminants” OR “Soil water retention” OR “Soil water holding capacity” OR “Pesticide residue” OR “Soil organic matter” OR “Soil aeration”) AND (“Sensory” OR “Taste” OR “Aroma” OR “Texture” OR “Appearance”) AND (“Tomato” OR “Solanum lycopersicum”).

Inclusion and exclusion criteria

The inclusion criteria for this review comprised peer-reviewed articles, studies focusing on the impact of soil health on tomato quality, articles published within the last 10 years to ensure the findings remain current, and publications in English that were in their final stage of publication.

The exclusion criteria encompassed studies unrelated to tomatoes, soil health, or sensory qualities; articles not published in English and those not peer-reviewed. Review papers, grey literature, textbooks, and articles without full-text availability were excluded from the study.

Search results

The literature search and screening process was conducted following the PRISMA 2020 guidelines [7] and is presented in Fig. 1. A total of 598 records were initially identified from three databases: Scopus (43), PubMed (18), and Taylor and Francis (537). After removing 8 duplicate records and 83 ineligible records through automation tools due to issues such as non-English language, irrelevant subject area, non-peer-reviewed status, or inappropriate publication type, 507 records proceeded to title screening.

Fig. 1.

PRISMA flowchart of literature search and screening [7]

From the title screening stage, 453 records were excluded, primarily because they were review papers or unrelated to the topic. The remaining 54 articles underwent abstract screening, resulting in the exclusion of 30 studies that lacked relevant soil data, crop focus, or sensory quality assessments. A total of 26 full-text articles were assessed for eligibility. Of these, 14 were excluded for reasons including being review papers, not aligning with the study’s objectives, lacking correlation analysis, or full-text inaccessibility.

Ultimately, 12 studies met all inclusion criteria and were incorporated into the systematic review. These studies provided empirical evidence on how soil health parameters such as macronutrients, organic matter, microbial activity, and contamination interact with key sensory attributes of tomatoes, including flavour, sweetness, aroma, texture, and overall acceptability.

Quality assessment

The methodological quality of the 12 experimental studies included in this review was assessed using the Joanna Briggs Institute (JBI) critical appraisal checklist for quasi-experimental studies. This tool provided a structured approach to evaluate each article’s relevance, methodological rigour, and reliability. It helped identify studies with clear objectives, robust methodologies, and appropriate data analysis, ensuring only high-quality evidence was included in the review [8]. It contained 8 items for a cross-sectional study that was used to assess the methodological quality of the studies in the systematic review. These tools help determine whether a study has the necessary rigor, reliability, and validity to be included in evidence synthesis.

Data extraction

A structured template was created to gather necessary details from each study, such as the study’s objective, treatments applied, parameters measured, key findings, and overall conclusions. The focus was on capturing information about soil nutrients (like macronutrients and micronutrients), soil management practices, microbial activity in the soil, and how these factors influence the sensory qualities of tomatoes, including their flavour, aroma, texture, and appearance. In cases where studies examined multiple treatments or conditions, each was documented separately to ensure every effect was properly highlighted. To maintain accuracy and consistency, all extracted data were carefully reviewed by a second and subsequently, a third person.

The findings were then grouped into themes, like the role of nutrients in enhancing sensory qualities, the effects of sustainable soil management, and the influence of soil microbial activity. For studies that were excluded, the reasons, such as irrelevance to tomato sensory attributes or incomplete methods, were captured.

Results and discussion

Results

Summary of sensory quality parameters assessed in selected studies

A review of the twelve selected studies revealed a range of sensory quality parameters assessed in relation to food crops, particularly tomatoes. From Table 1, two of the reviewed studies, Quddus et al. [9] and Hashem et al. [10], were comprehensive in their assessment, evaluating all four major sensory qualities for the purpose of this review: flavour, aroma, texture, and appearance. These studies provide a holistic view of consumer-perceived quality, acknowledging the multifaceted nature of sensory evaluation. Six other studies assessed three out of the four key sensory parameters. Suthar et al. [11], Bhardwaj et al. [12], Baroutkoob et al. [13], and Youssef and Eissa [14] each focused on flavour, texture, and appearance, omitting aroma. On the other hand, Ma et al. [15] and Zhang et al. [16] assessed flavour, aroma, and appearance, leaving out texture.

Table 1.

Summary of sensory quality parameters assessed in selected studies

Sensory qualities assessed
References	Flavour	Aroma	Texture	Appearance
Suthar et al. [11]	✓	✘	✓	✓
Quddus et al. [9]	✓	✓	✓	✓
Filho et al. [17]	✓	✘	✘	✓
Baroutkoob et al. [13]	✓	✘	✓	✓
Bhardwaj et al. [12]	✓	✘	✓	✓
Hashem et al. [10]	✓	✓	✓	✓
Youssef and Eissa [14]	✓	✘	✓	✓
Li et al. [19]	✓	✘	✘	✓
Zheng et al. [18]	✓	✓	✘	✘
Ma et al. [15]	✓	✓	✘	✓
Zhang et al. [16]	✓	✓	✘	✓
Casa and Rouphael [20]	✓	✘	✘	✓

✓ means assessed, ✘ means not assessed

Four studies were more limited in scope, assessing only two sensory parameters. Filho et al. [17] concentrated on flavour and appearance, possibly reflecting an emphasis on the initial sensory impression formed by consumers. Zheng et al. [19], by contrast, focused on flavour and aroma, which are both crucial to the gustatory experience. Li et al. [19] assessed flavour and appearance, the same as Casa & Rouphael [20], who also considered both flavour and appearance, reinforcing the importance of both taste and visual cues in determining perceived quality.

Flavour was the most consistently assessed parameter across studies, appearing in nearly all of them. Appearance was also widely considered because of its influence at the point of sale and initial consumer attraction. Aroma and texture, while slightly less frequently evaluated.

Descriptive results of included studies or characteristics of included studies

Table 2 below provides a summary of the studies exploring how different soil treatments and management practices impact tomato growth, yield, and quality. A wide range of approaches was investigated, including soil amendments like biochar, biogas slurry, and organic nutrient solutions, as well as nutrient-specific applications such as magnesium, phosphorus, and potassium nitrate. Some studies tested innovative techniques, like foliar sprays of cyanobacteria [12] and post-infiltration soil aeration [19]. Others focused on broader issues, such as the effects of heavy metal contamination in soil or the role of irrigation strategies like partial root-zone drying [10, 20].

Table 2.

Summary of key characteristics of the 12 studies included in the review

Reference	Aim of the paper	Treatments in the study	Parameters measured	Outcome of the treatments on fruit qualities measured
Bhardwaj et al. [12]	To evaluate the impact of foliar sprays of cyanobacterial formulations on tomato plant growth and fruit quality under protected cultivation.	Weekly foliar applications of two cyanobacterial formulations (Anabaena laxa and Anabaena torulosa)	Plant growth parameters, fruit yield, fruit quality attributes, microbiological properties	Both formulations enhanced plant growth, fruit yield, and quality. Anabaena laxa significantly improved microbiological properties.
Baroutkoob et al. [13]	To assess the impact of soil texture and phosphorus content on tomato plant properties.	Clayey and sandy soils; phosphorus treatments (non-phosphorus, calcium phosphate, nano-hydroxyapatite)	Yield parameters (fruit weight, juice content, antioxidant activity), shoot fresh weight, root length, phosphorus concentration	CaP₂ treatment in clayey soil led to increases in fruit number (50%), fruit weight (29%), and yield (91%) compared to sandy soil. PN1 treatment resulted in the highest shoot weight.
Filho et al. [17]	To investigate the combined effects of biochar soil amendment and foliar application of potassium nitrate on tomato growth, yield, and physiology under varying irrigation regimes.	Biochar soil amendment, foliar KNO₃ application, and full or deficit irrigation regimes	Plant growth, physiological (photosynthesis, stomatal conductance), yield (fruit number, weight), fruit quality (soluble solids, acidity, firmness)	Biochar improved yield and fruit quality under deficit irrigation; KNO₃ improved some physiological parameters but not overall yield.
Ma et al. [15]	To investigate the impact of organic nutrient solutions on nutrient content and aromatic volatiles in tomato fruits.	Organic nutrient solutions derived from manure (pig, cow, sheep)	Soluble sugar, organic acid, lycopene, ascorbic acid, soluble protein, aromatic volatiles	ONS significantly increased soluble sugar, organic acid, lycopene, ascorbic acid, soluble protein, and aroma content. The best supplementation was 12 L per plant.
Zheng et al. [18]	To assess the effects of biogas slurry irrigation on tomato yield, quality, and soil environment.	Biogas slurry irrigation replacing inorganic fertilizers	Physiological indexes, ecological indexes, yield, fruit quality, soil environment	Biogas slurry increased tomato yield, promoted healthy growth, and improved soil conditions, proving a viable alternative to inorganic fertilizers.
Zhang et al. [16]	To evaluate the combined effects of irrigation levels and biochar application on soil properties, plant growth, yield, and fruit quality in greenhouse tomatoes.	Full, moderate, and severe deficit irrigation with 0%, 1%, and 2% biochar	Soil bulk density, porosity, plant growth, yield, fruit quality (soluble solids, acidity)	Biochar under full and severe deficit irrigation improved yield, while moderate deficit with biochar reduced growth and yield slightly.
Suthar et al. [11]	To investigate the effects of bamboo biochar on tomato plant growth and fruit quality.	Bamboo biochar at 0%, 1%, and 3% produced at 300 °C, 450 °C, and 600 °C	Plant growth indices, glucose, fructose, soluble solids, ascorbic acid, sugar-to-acid ratios	Biochar at 300 °C (3%) and 450 °C (1%) improved plant growth and fruit quality, with higher glucose, fructose, soluble solids, and ascorbic acid.
Li et al. [19]	To investigate the effects of post-infiltration soil aeration at various growth stages on the growth and fruit quality of drip-irrigated potted tomato plants.	Soil aeration by injecting 2.5 L of air into each pot through the drip tubing immediately after irrigation during five different periods: 27–33, 34–57, 58–85, 86–99, and 27–99 days after sowing (DAS).	Root dry weight and activity, yield, soluble solids, vitamin C content, titratable acidity, shape, and firmness.	Post-infiltration aeration during fruit setting and enlargement improved yield, root activity, and fruit quality by increasing soluble solids and vitamin C, enhancing shape and firmness, and lowering titratable acidity.
Hashem et al. [10]	To assess the impact of soil contamination with heavy metals on the physico-biochemical properties of tomato fruits.	Tomato plants cultivated in soil contaminated with industrial effluents containing heavy metals such as Cd, Co, Ni, and Pb.	Fruit length, diameter, volume, fresh and dry weights, total soluble solids, titratable acidity, lycopene, carbohydrates, total phenols, flavonoids, micro- and macronutrients, and residual heavy metal content in fruits.	Soil heavy-metal contamination reduced tomato size, weight, TSS, acidity, lycopene, ascorbic acid, micronutrients, and carbohydrates, while increasing phenols, flavonoids, and heavy-metal residues in the fruits compared with uncontaminated soils.
Casa and Rouphael [20]	To investigate the effects of partial root-zone drying irrigation on yield, fruit quality, and water-use efficiency in processing tomatoes.	Compared partial root-zone drying (PRD) irrigation with full irrigation (FI) and deficit irrigation (DI).	Yield, water-use efficiency (WUE), soluble sugar content, organic acid content.	PRD cut marketable yield by 52% relative to FI but improved WUE, increased soluble sugars by 4.5%, reduced organic acids by 5.3%, and enhanced the sugar–acid ratio and fruit quality.
Youssef and Eissa [14]	To compare the effects of organic and inorganic nutrition on tomato growth, yield, and fruit quality.	Applied combinations of rabbit manure, rock phosphate, feldspar, and bio-fertilizers (Bio-N-P-K) versus conventional inorganic fertilization.	Fruit yield, nutrient concentrations in leaves (N, P, K), and fruit quality attributes.	The combination of organic amendments and bio-fertilizers increased fruit yield by 30% compared to inorganic fertilization. Nutrient concentrations in leaves were higher, and overall fruit quality was improved with organic treatments.
Quddus et al. [9]	To determine the effective dose of magnesium (Mg) to improve yield and quality and assess nutrient uptake and use efficiency of tomato.	Five Mg treatments: 0 (control), 4, 8, 12, and 16 kg·ha⁻¹.	Fruit number per plant, average fruit weight, total fruit yield, nutrient uptake, and use efficiency.	Application of 12 kg·ha⁻¹ Mg produced the highest fruit number per plant (41.1), average fruit weight (74.3 g), and total fruit yield (69.7 t·ha⁻¹).

The extraction from Table 2 shows how these treatments can shape tomato quality, including flavour, aroma, texture, and nutritional value. Biochar and organic amendments consistently improved yield and sensory qualities, such as sweetness and acidity [17, 11]. In contrast, heavy metal-contaminated soils negatively affected fruit size, flavour, and overall quality [10]. Studies also showed the importance of balancing water and nutrient management. Partial root-zone drying, for instance, increased water-use efficiency and enhanced the sugar/acid balance in tomatoes [20].

Effect of health parameters on sensory quality of tomatoes

The twelve included studies after the review process of the initial 598 papers assessed a wide range of soil attributes, including nutrient content, organic matter, pH, texture, enzymatic activities, and contamination levels, and their influence on sensory indicators such as flavour, aroma, appearance, and texture.

In Table 3, Suthar et al. [11] measured soil nutrient concentrations (NO₃-N, P, Ca, and Mg) and reported that tomatoes cultivated with lower temperature biochars (300 °C) exhibited firmer texture and darker red colour, which corresponded with higher sugar levels and enhanced flavour. The sugar-to-acid ratio was significantly higher in biochar-amended soils. Quddus et al. [9] evaluated several soil parameters, including pH, organic matter, total nitrogen, exchangeable Ca and Mg, and multiple nutrients (N, P, K, S, Zn, B). They found that higher magnesium content improved total soluble solids (TSS), vitamin C, and protein content in tomato fruits. Additionally, optimal soil pH enhanced nutrient availability, thereby improving taste and firmness. Organic matter contributed to nutrient retention, positively affecting flavour and texture, while nitrogen availability enhanced sweetness and aroma.

Table 3.

Soil health parameters, sensory quality indicators, and their interactions in tomato production: data extraction

Reference	Soil health parameters measured	Tomato sensory quality parameters measured	Impact of soil health on sensory quality
Suthar et al. [11]	Nutrient concentrations (NO₃-N, P, Ca, and Mg).	1. Appearance 2. Texture 3. Taste	1. Firmer texture and darker red colour were associated with tomatoes grown in lower temperature biochars (300 °C), which also exhibited higher levels of sugars and better flavour qualities. 2. The sugar-to-acid ratio was significantly higher in tomatoes from treatments with biochar, indicating an improvement in sensory perceptions, such as sweetness, which impacts overall flavour.
Quddus et al. [9]	1. pH 2. Organic matter 3. Total nitrogen (N) 4. Exchangeable calcium (Ca) and magnesium (Mg) 5. Nutrient content (N, P, K, S, Zn, B)	1.Flavour 2. Aroma 3. Texture 4. Appearance	1. Higher levels of magnesium improved fruit quality traits, enhancing attributes such as TSS, vitamin C, and protein content. 2. Optimal pH levels contributed to better nutrient availability, influencing traits like taste and firmness. 3. Increased organic matter positively impacted overall nutrient retention in the soil, which in turn enhanced flavour and texture. 4. Adequate levels of nitrogen promoted better growth, which correlated with improved sensory traits such as sweetness and aroma.
Filho et al. [17]	1. pH 2. Available phosphorus (P) 3. Available potassium (K) 4. Exchangeable calcium (Ca) 5. Exchangeable magnesium (Mg) 6. Organic carbon content (C-org)	1. Flavour 2. Appearance	1. Higher pH was associated with improved fruit firmness. 2. Increased organic carbon content and nutrient availability (K, Ca, Mg) enhanced total soluble solids and lycopene content. 3. Enhanced available potassium improved overall fruit quality attributes, including firmness and lycopene levels.
Baroutkoob et al. [13]	1. Soil texture (clay and sandy) 2. Phosphorus availability (different sources of phosphorus, including calcium phosphate and nano-hydroxyapatite)	1. Texture 2. Appearance	1. The application of nano-hydroxyapatite (PN1) led to improved colour indices (L*, a*, b*) in comparison to other phosphorus sources, indicating a potentially better appearance of the fruit. 2. Clayey soil exhibited larger fruit sizes and higher weight compared to sandy soil, enhancing overall appearance and potential consumer appeal. 3. The use of calcium phosphate at the correct dosages (CaP1 and CaP2) also positively affected the quality traits assessed, such as fruit weight and firmness.
Bhardwaj et al. [12]	1. pH 2. Organic carbon 3. Available nitrogen (N) 4. Iron (Fe) content 5. Zinc (Zn) content 6. Soil urease activity 7. Soil dehydrogenase activity	1. Flavour 2. Texture 3. Appearance	1. Higher organic carbon content in soil positively influenced the fresh fruit weight. 2. Increased soil urease activity was associated with improved fruit firmness and ascorbic acid content. 3. Enhanced soil dehydrogenase activity correlated with higher yields and better fruit quality parameters, such as total soluble solids and titratable acidity.
Hashem et al. [10]	Heavy metal content (Cd, Co, Ni, Pb).	1. Flavour 2. Aroma 3. Texture 4. Appearance	1. Soil contamination with heavy metals significantly reduced fruit length, diameter, volume, and fresh/dry weights, which are critical for overall fruit quality. 2. Total soluble solids (TSS) and the TSS/TA ratio were adversely affected, making fruits less ideal for fresh consumption due to poor flavour. 3. Lycopene content was decreased in fruits from contaminated soil, negatively impacting colour value and overall sensory appeal. 4. Carbohydrates and soluble sugars were also lower in fruits grown in contaminated soil, affecting taste and texture.
Youssef and Eissa [14]	1. Available P 2. Available K 3. Available Nitrogen 4. pH 5. CaCO₃ 6. CEC 7. Total Nitrogen 8. Organic Carbon	1. Texture 2. Appearance 3. Flavour	1. Higher organic matter improved nutrient availability in the soil, which consequently improved fruit quality (taste, appearance). 2. Better tomato growth and quality are influenced by improved soil health from organic additions, which also improves the fruit’s flavour and sensory profile.
Li et al. [19]	1. Total nitrogen 2. Organic matter content 3. Soil density 4. Soil porosity	1. Appearance 2. Flavour	1. High soil aeration led to improved nutrient availability. This further resulted in improved plant growth and fruit quality. 2. Soil aeration was found to improve the fruit’s shape and firmness, potentially making it more appealing to consumers. 3. Soil aeration decreased titratable acidity in the tomato fruit, thereby improving taste.
Zheng et al. [18]	1. Soil microstructure (aeration) 2. Total Nitrogen Content 3. Soil organic matter 4. Soil saturated hydraulic conductivity	1. Flavour 2. Aroma	1. Organic treatment of the soil has improved the soil’s environmental conditions and has a positive correlation with fruit quality. 2. The organic soil amendments improved tomato fruit sugar-acid ratio, soluble sugar, and titratable acid contents for an overall improved taste.
Ma et al. [15]	1. pH 2. Electrical conductance 3. Total nitrogen 4. Total Phosphorus 5. Total potassium 6. NH₄ 7. NO₃ 8. Organic matter	1. Flavour 2. Aroma 3. Appearance	1. Organic nutrient solution significantly increased the soluble sugar, lycopene, and soluble protein content of fruit compared to the control treatment. 2. Sugar and ascorbic acid contents and the sugar-acid ratio also increased for the organic nutrient treatment. 3. The organic nutrient supplementation has a positive correlation with the nutrients and characteristic aroma content of the tomato fruit.
Zhang et al. [16]	1. Nitrogen content 2. Magnesium content 3. pH 4. Calcium content 5. CEC 6. Soil density 7. Texture 8. Organic matter	1. Flavour 2. Aroma 3. Appearance	1. Application of biochar had a positive correlation with sensory parameters of the tomato fruit, although not statistically significant
Casa and Rouphael [20]	1. Exchangeable 2. Phosphorus 3. Organic matter content 4. Available Potassium 5.Texture 6. Soil density	1. Flavour 2. Appearance	1. Deficit irrigation and partial root-zone drying improved fruit quality in terms of total soluble solids contents (TSSC) as well as titratable acidity (TA) and juice pH, but not lycopene concentrations or fruit colour

Filho et al. [17] assessed pH, available P and K, exchangeable Ca and Mg, and organic carbon (Table 3). Their review indicated that higher pH values were associated with improved fruit firmness. Elevated organic carbon and available nutrients enhanced TSS and lycopene content, while potassium availability contributed to improved firmness and lycopene accumulation. Baroutkoob et al. [13] examined the effects of soil texture and phosphorus sources (including calcium phosphate and nano-hydroxyapatite). They observed that nano-hydroxyapatite significantly improved fruit colour indices (L*- lightness, a*- red–green balance, b*- yellow–blue balance), therefore enhancing appearance. Clayey soils produced larger, heavier fruits compared to sandy soils. Application of calcium phosphate, particularly at appropriate dosages, improved fruit weight and firmness.

Bhardwaj et al. [12] included parameters such as soil pH, organic carbon, available N, Fe, Zn, and enzymatic activities (urease and dehydrogenase). Increased organic carbon enhanced fresh fruit weight, while urease activity was linked to better fruit firmness and higher ascorbic acid content. Soil dehydrogenase activity correlated positively with yield and fruit quality, particularly TSS and titratable acidity. Hashem et al. [10] focused on heavy metal contamination (Cd, Co, Ni, Pb) and its adverse effects. Contaminated soils significantly reduced fruit length, diameter, volume, and weight, with negative impacts on TSS, sugar-to-acid ratio, lycopene, carbohydrates, and soluble sugars. These reductions translated to poor flavour, colour, and texture, making the fruits less suitable for fresh consumption.

Youssef and Eissa [14] measured available P, K, nitrogen (total and available), pH, CaCO₃, CEC, and organic carbon. They found that improved organic matter enhanced nutrient availability and positively influenced tomato flavour and appearance (Table 3). Overall, tomato growth and sensory quality were better in organically amended soils. Li et al. [19] assessed total nitrogen, organic matter content, soil density, and porosity. They found that improved soil aeration enhanced nutrient availability, which subsequently improved plant growth and fruit quality. Fruits grown under better-aerated conditions exhibited improved shape and firmness and had lower titratable acidity, which enhanced taste.

Zheng et al. [18] considered soil microstructure, total nitrogen, organic matter, and saturated hydraulic conductivity. Organic treatments improved soil conditions and were positively correlated with better fruit quality, particularly in terms of sugar-acid balance, soluble sugar, and acidity, leading to enhanced flavour. Ma et al. [15] measured pH, electrical conductance, total N, P, K, NH₄⁺, NO₃⁻, and organic matter. They observed that organic nutrient solutions significantly increased soluble sugars, lycopene, soluble protein, and ascorbic acid content. The sugar-acid ratio and aroma profile were also enhanced under organic treatments.

Zhang et al. [16] included nitrogen, magnesium, pH, calcium, CEC, soil density, texture, and organic matter in their study. The application of biochar was positively associated with improved sensory parameters, although the effects were not statistically significant. Finally, Casa and Rouphael [20] evaluated exchangeable phosphorus, organic matter, available potassium, texture, and soil density. Deficit irrigation and partial root-zone drying techniques were found to improve total soluble solids, titratable acidity, and juice pH, although lycopene content and fruit colour remained unaffected.

Across the 12 studies, key soil parameters, particularly organic matter, nutrient content (N, P, K, Mg), soil pH, and enzymatic activity, were consistently associated with improvements in sensory quality attributes such as taste, firmness, aroma, and appearance. Soil contamination, on the other hand, had detrimental effects on all measured sensory indicators.

Quality assessment of studies

All 12 studies (100%) explicitly stated the cause-and-effect relationship between the intervention and the outcomes being measured. Every study also included a control group for comparison, indicating a strong experimental design. Nine studies (75%) clearly reported that participants or experimental units were similar at baseline, enhancing internal validity, while three studies [12, 10, 18], did not provide sufficient information on participant comparability.

All the studies reported on additional treatments or interventions, ensuring that the observed effects could be attributed to the main experimental variable. However, only six studies (50%) measured outcomes both before and after the intervention. The remaining studies either did not provide pre-intervention data or assessed outcomes only post-intervention. Despite this, all 12 studies measured outcomes in the same way for both intervention and control groups, indicating good methodological consistency. They also reported that outcomes were measured in a reliable and reproducible manner. Furthermore, every study employed appropriate statistical methods to analyze the data, further strengthening the reliability of their conclusions.

Limitations of the study

This review has a number of limitations. A number of studies did not measure outcomes both before and after the intervention, reducing the ability to detect true changes attributable to soil conditions. In some cases, participant or sample similarity was unclear, which may introduce variability unrelated to soil treatments. A few studies also lacked clarity on whether baseline characteristics were consistently controlled, and some did not report whether additional treatments or external factors were fully monitored. While outcome measurements were generally consistent and reliable, the absence of pre-post assessments in several studies limits causal interpretation.

Conclusion and recommendations

This systematic review establishes a clear link between soil health parameters and the sensory quality of tomatoes. Treatments such as biochar and biogas slurry not only improved soil physicochemical properties and microbial activity but also led to significant enhancements in tomato fruit quality attributes like flavour, aroma, firmness, and nutritional content. The reviewed studies show that factors like nutrient availability, enzymatic activity, and pH balance in soils are crucial in modulating these sensory outcomes. However, the adverse effects of heavy metal contamination and the context-specific nature of certain amendments highlight the importance of tailoring soil management practices to local conditions. Thus, soil is more than just a growth medium; it is a vital determinant of crop quality and consumer acceptability.

In light of these findings, it is recommended that farmers and agricultural stakeholders adopt integrated soil management strategies that combine organic amendments, judicious irrigation techniques, and routine soil quality monitoring. Policies promoting the use of biochar and biogas slurry should consider amendment type, application rate, and local soil characteristics to avoid negative impacts such as nutrient lockup or soil alkalinity. Furthermore, investments in farmer training and extension services are essential to support the implementation of sustainable practices that enhance both yield and food quality. Future research should focus on long-term trials that evaluate the cumulative impact of amendments, while also incorporating sensory evaluations and nutritional profiling. Such interdisciplinary approaches will strengthen the evidence base for developing climate-resilient, health-enhancing food production systems. Additionally, extension officers, policymakers, and researchers should collaborate to develop soil health monitoring frameworks, promote evidence-based sustainable fertilizer policies, and strengthen farmer capacity through targeted training programs that support improved tomato quality. Overall, these efforts support key global sustainability targets especially SDG 2, SDG 12, SDG 13, and SDG 15 by protecting soil health, improving food quality, and promoting more sustainable farming practices (Table 4).

Table 4.

Critical appraisal of experimental study quality using the JBI checklist: quality assessment

References	Assessment questions
	Is the cause and effect clearly stated?	Was there a control group?	Were participants similar?	Were other treatments measured aside the main interventions?	Were outcomes measured pre and post intervention?	Were the outcomes measured in the same way?	Were outcomes measured in a reliable way?	Was appropriate statistical analysis used?
Suthar et al. [11]	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes
Quddus et al. [9]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Filho et al. [17]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Baroutkoob et al. [13]	Yes	Yes	Yes	Yes	Unclear	Yes	Yes	Yes
Bhardwaj et al. [12]	Yes	Yes	Unclear	Yes	Yes	Yes	Yes	Yes
Hashem et al. [10]	Yes	Yes	Unclear	Yes	No	Yes	Yes	Yes
Youssef and Eissa [14]	Yes	Yes	N/A	Yes	No	Yes	Yes	Yes
Li et al. [19]	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes
Zheng et al. [18]	Yes	Yes	Unclear	Yes	Yes	Yes	Yes	Yes
Ma et al. [15]	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes
Zhang et al. [16]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Casa and Rouphael [20]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes

Barker et al. [21]

Discussion

Summary of key characteristics of the 12 studies included in the review

Among the notable treatments studied, biochar emerged as a prominent amendment that enhances tomato growth and yield. Filho et al. [17] and Suthar et al. [11] reveal that such amendments enhance soil physicochemical properties, microbial activity, and nutrient availability. These benefits translate to improvements in total soluble solids, ascorbic acid concentration, and fruit firmness. Guo et al. [22] also stated in their research that biochar can limit the need for nitrogen (N) fertilizers without compromising yield, suggesting that biochar improves nitrogen retention and turnover because of its influence on soil microbial properties. Similarly, Obadi et al. [23] found that biochar application resulted in significant improvements in tomato morpho-physiological traits and fruit quality under certain stress conditions. However, caution is warranted regarding excessive biochar application, as high pH levels may adversely affect nutrient availability [23, 24].

The benefits of the biochar application may also attenuate over time due to biochar aging, necessitating periodic application. Notably, the efficacy of biochar is contingent upon its feedstock and pyrolysis temperature, with wood- and straw-derived biochar produced at 401–500 °C yielding the most favorable outcomes. While most studies report positive outcomes, the variability in biochar type, application rate, and environmental context explains discrepancies such as the weak effects observed by Zhang et al. [16]. This highlights the importance of considering local soil properties and amendment protocols when interpreting biochar efficacy.

In addition to biochar applications, the use of biogas slurry has been evaluated for its nutrient contributions. Biogas slurry is rich in essential nutrients like nitrogen (N), phosphorus (P), and potassium (K), which are foundational for crop growth. Zheng et al. [18] demonstrated that biogas slurry combined with irrigation techniques could enhance tomato quality while improving water use efficiency, which is consistent with the findings from Zheng et al. [25]. Furthermore, findings by You et al. [26] emphasize that the nitrogen supplied from biogas slurry directly correlates with improved yields during the growing season, while P and K supplies can persist into subsequent years, providing longer-term benefits. However, variability in nutrient composition of biogas digestates has been highlighted by Mupambwa et al. [27] to indicate that these variations can lead to reduced yield in hydroponic systems, underscoring the necessity for balanced nutrient management.

The role of macro- and micronutrients in modulating fruit quality was evident in studies focusing on magnesium, phosphorus and potassium nitrate [9, 13, 17]. The application of 12 kg ha⁻¹ magnesium yielded the highest improvements in both yield and quality indices, echoing findings from Javaria et al. [28] that underscore the importance of balanced mineral nutrition, particularly potassium and magnesium, in enhancing tomato sensory attributes. Interestingly, the standalone application of potassium nitrate yielded limited effects on fruit yield in Filho et al.’s [17] study, suggesting that nutrient applications are most effective when embedded within holistic soil amendment strategies.

A critical counterpoint in this synthesis is the deleterious impact of soil contamination, specifically heavy metal accumulation, on fruit quality and safety. Hashem et al. [10] reported substantial reductions in fruit size and nutritional content, alongside elevated toxic residues in tomatoes cultivated in contaminated soils. These findings align with research by Tang et al. [29] that indicates that soils contaminated with heavy metals yield tomatoes of diminished size and quality, further emphasizing the need for monitoring soil health alongside treatment application. This is also similar to earlier reports by Sharaf & Salehi [30], emphasizing the urgent need for stringent soil monitoring and the implementation of remediation strategies in high-risk agricultural zones. This complexity illustrates the multitiered challenges faced in optimizing tomato production careful attentiveness to both soil amendments and broader environmental stresses is essential. The variability in contamination effects also suggests that some soil amendments may partially mitigate negative impacts, but inconsistent reporting across studies prevents a definitive conclusion. This indicates the importance of standardized measurement and reporting in future research.

Soil health parameters, sensory quality indicators, and their interactions in tomato production: data extraction

The systematic review demonstrates a positive association between key soil health parameters, particularly organic matter, macro- and micronutrient levels (N, P, K, Mg), pH, enzymatic activity, and soil structure and improvements in sensory quality traits of tomatoes such as flavour, aroma, appearance, and texture. The synthesis of these studies supports the assertion that soil quality fundamentally underpins the organoleptic appeal of tomatoes, aligning with the growing recognition that soil is not merely a substrate but a determinant of food quality and health [31]. However, inconsistencies in measurement units, reporting methods, and study design limit the ability to generalize these findings fully. Some studies reported only qualitative improvements or lacked statistical verification, highlighting a key limitation of the current evidence base.

The influence of nutrient-rich, organically amended, or biochar-enhanced soils on sensory parameters such as sugar content, firmness, and flavour aligns with findings from Diacono and Montemurro [32], who documented those organic amendments enhanced soil fertility and improved fruit taste and nutritional profiles across a range of crops. Studies like Suthar et al. [11], Quddus et al. [9], and Ma et al. [15] highlight the critical role of organic matter in nutrient retention and availability, which underpins improvements in taste, aroma, and colour. These findings echo earlier work by Toor et al. [33], who demonstrated that organically grown tomatoes tend to contain more sugars and phenolic compounds, both vital for flavour development.

Hashem et al. [10] examined the detrimental effects of soil contamination, particularly with heavy metals such as Cd and Pb, which substantially diminish fruit size, sugar content, lycopene levels, and overall flavour. These findings are corroborated by research from Sharma et al. [34], who observed that heavy metal toxicity not only suppresses plant growth and yield but also negatively impacts key sensory traits, particularly those related to sweetness and aroma. The implications are critical for regions plagued by soil pollution, as even marginal contamination can undermine not only yield but also market acceptability of the produce.

Soil pH emerges as a recurrently significant variable across multiple studies [9, 17], with optimal pH levels enhancing nutrient solubility and root uptake, which in turn translates to better fruit taste and texture. This observation aligns with recommendations by Marschner [35], who emphasized the pH-dependent availability of essential nutrients such as phosphorus, magnesium, and micronutrients like zinc and iron, each of which has roles in the development of tomato biochemical and sensory profiles.

A particularly novel insight from Baroutkoob et al. [13] and Bhardwaj et al. [12] involves the impact of enzymatic soil activity and phosphorus nano-fertilization on tomato sensory outcomes. Urease and dehydrogenase activities serve as proxies for microbial health and biochemical turnover in soils, and their positive correlations with sensory parameters suggest that biotic soil health may be as critical as its physicochemical dimensions. This resonates with research by Liu et al. [36], who demonstrated that soil biological activity directly influences nutrient mineralization and phytonutrient expression in vegetables.

Not all findings were unequivocally supportive. Zhang et al. [16] reported only weak and statistically non-significant effects of biochar amendment on sensory quality, indicating that outcomes may be context-specific and dependent on factors such as soil type, crop variety, and amendment application rate. These nuances reflect those highlighted by Glaser et al. [37], who noted the variability in biochar’s agronomic benefits based on regional soil characteristics and climate.

Moreover, while the majority of studies confirmed that organically managed soils consistently enhance flavour and nutritional qualities, the research by Casa and Rouphael [20] showed that irrigation techniques such as deficit irrigation and partial root-zone drying improved certain sensory traits (TSS and TA), independent of major nutrient dynamics. This suggests that water availability and stress conditions might mediate secondary metabolite production in tomato fruits, as previously theorized by Mitchell [38].

The findings of this review collectively underscore the multifaceted nature of soil-crop quality interactions. They point to the need for integrated soil fertility and land management strategies that simultaneously promote nutrient adequacy, biological activity, and contamination avoidance. The policy and agronomic implications are profound: improving soil health not only ensures sustainable yields but also enhances food quality, potentially influencing consumer preferences, market value, and nutritional outcomes.

Author contributions

J.B. - Conceptualization, collection of literature and analysis and draft manuscriptL.N.A.S.- Conceptualization, supervision and review of the manuscriptL.N.E.A - Conceptualization, supervision and review of the manuscriptC.A- Conceptualization, supervision and review of the manuscriptH.E.L- Conceptualization, supervision and review of the manuscriptR.A.A - Conceptualization, supervision and review of the manuscript.

Funding

This research was supported by the American Heart Association under the Food EDU Fellowship.

Data availability

Data is available upon request.

Declarations

Consent for publication

Since this study is not attempting to re-publish/publish any third party or author’s previously published material, this section does not apply.

Competing interests

The authors declare no competing interests.