A Review on the Mechanism of Soil Flame Disinfection and the Precise Control Technology of the Device

Abstract

Soil disinfection is of great significance in reducing soil pests and weeds, overcoming the problem of crop continuous cropping obstacles, and ensuring the quality and safety of agricultural products. Soil flame disinfection technology, as a supplementary soil disinfection method that can be incorporated into an integrated plant protection system, has attracted much attention in recent years due to its characteristics of low resistance, greenness, environmental friendliness, and high efficiency. However, soil flame disinfection can also have a certain impact on soil organic matter and microbial communities, which is a core challenge that limits the promotion of flame disinfection technology. Clarifying the mechanism and temperature distribution of flame disinfection, accurately controlling flame disinfection parameters, can not only kill harmful organisms in soil, but also minimize damage to soil organic matter and microbial communities is the current research focus. This paper presents a comprehensive summary and discussion of the research progress regarding the mechanism of soil flame disinfection technology, the distribution of temperature fields, and the precise control technology for disinfection machines. It thoroughly elaborates on the efficacy of flame in eliminating typical soil-borne diseases and pests, the destructive impact of flame on soil organic matter and beneficial microbial communities, as well as the current status of research and development on soil flame disinfection devices. Additionally, it explores the pressing technical challenges that remain to be addressed. The article then discusses the future market prospects of soil flame disinfection equipment, focusing on key technological breakthroughs and opportunities, providing theoretical support for the next research, optimization and promotion of soil flame disinfection technology.

1. Introduction

Soil-borne pests and diseases refer to organisms that survive in the soil environment and cause harm to plants, which mainly include two categories: pathogenic microorganisms (such as fungi, bacteria, viruses, etc.) and the other is pests (such as nematodes, cutworms, etc.). Under suitable conditions, these pests and diseases can invade crops through the roots or stems, triggering soil-borne diseases and spreading over large areas through the soil [1,2,3,4,5]. Among various crop pests and diseases, those originating from the soil often cause the most severe damage. Furthermore, there are many types of pathogenic organisms that induce soil-borne diseases [6], and different types of pathogens have different incubation periods and onset periods, which significantly increases the difficulty of controlling soil-borne pests and diseases.

Currently, the control methods for soil-borne pests and diseases include agricultural control, physical control, chemical control, and biological control [7]. Among these, chemical control is the most commonly used method due to its high efficacy and operational simplicity. However, the extensive use of chemical agents pollutes the farmland environment and enhances the resistance of pathogenic microorganisms and pests, making it more difficult to completely eliminate the diseases and pests. This not only affects the yield and quality of vegetables but also poses a serious threat to the quality and safety of agricultural products [8,9]. Therefore, finding pollution-free control methods for soil-borne pests and diseases is an urgent problem that needs to be solved by agricultural science and technology workers. Agricultural control employs methods such as crop rotation, soil amendment, and tillage adjustment to disrupt the life cycle of pests/pathogens. However, this approach requires a long duration and it is difficult to achieve the ideal effect of pest and disease control in the short term. Biological control utilizes beneficial microorganisms (e.g., Trichoderma, Bacillus) or natural enemies to inhibit pathogens. It leaves no chemical residues; however, its effects are slow and susceptible to influences from soil pH and moisture. Physical control—such as solarization, flame disinfection, steaming and microwave treatment—offers chemical-free solutions. Given the current global demand for environmental protection, the international research trend has increasingly leaned toward physical control strategies. Solarization typically leverages sustained high temperatures in summer to kill soil-borne pathogenic organisms, but it is highly dependent on weather conditions. Steaming involves rapidly penetrating soil pores with high-pressure steam. Compared to the long-term agricultural control methods, it has the advantage of acting quickly and having a short recovery period after treatment. However, it has a limited penetration depth in the soil and extremely strict requirements for the operation of high-pressure equipment. Microwave treatment achieves sterilization by generating heat through microwave irradiation; however, this technology requires high professional expertise, and the manufacturing and operational costs of disinfection equipment are relatively high [10]. Flame disinfection, with its advantages of high efficiency, no chemical residue, simple operation, and wide application range, shows broad application prospects. Flame soil disinfection relies on high temperatures to effectively eliminate pathogens and pests, which consequently impacts soil organic matter and beneficial microbial communities. Relevant studies have demonstrated distinct effects of flame intensity on soil micro-organisms [11]: low-intensity flames (≤500 °C) induce a temporary 15–20% reduction in beneficial bacterial populations in the surface soil, with recovery occurring within three months; in contrast, high-intensity flames (>800 °C) lead to a significant 40–50% de-crease in microbial biomass, and the recovery period may extend up to six months. Therefore, a comprehensive understanding of the dual effects of flame soil disinfection on pests/pathogens and soil microorganisms—specifically, how to achieve effective pest control via flame while minimizing damage to the beneficial soil ecosystem—is crucial for the optimization and widespread application of this disinfection technology.

Under this background, clarifying the impact of soil flame disinfection technology on soil nutrients and the structure of beneficial microbial communities, analyzing the distribution of soil temperature fields, and constructing a precise control model for flame disinfection equipment are of great significance for improving the comprehensive promotion of soil flame disinfection technology. These efforts can achieve efficient elimination of harmful organisms in the soil while minimizing the negative impact on soil organic matter and beneficial microbial communities. In addition, sorting out the current status and application of soil flame disinfection equipment research and development is of great significance for promoting the further development of soil physical disinfection technology.

Existing reviews either focus solely on a single influencing factor of flame disinfection technology or lack the integration of the latest research findings (post-2020). This review provides a comprehensive and systematic overview of flame disinfection technology, its disinfection mechanisms, and the development of disinfection equipment published between 2016 and 2025. It fills the gap in interdisciplinary integration, clarifies the trade-off relationship between pathogen elimination and soil ecological protection, and highlights the need for long-term efficacy studies and alternative application strategies—aspects often overlooked in previous reviews. Furthermore, a technical roadmap of “mechanism refinement-intelligent control–sustainable integration” is proposed to guide future research, rather than merely summarizing existing achievements. The aim is to assess the application potential and limitations of this technology within integrated plant protection systems, provide theoretical support for improving its disinfection effect and utilization efficiency, as well as promoting further research, application, and popularization.

During the initial phase of manuscript preparation, the authors employed the large language model “DeepSeek V3.2” (developed by DeepSeek, a Chinese AI company) to assist in the preliminary retrieval and summarization of relevant literature on soil disinfection technologies. It is important to note that all outputs generated by the AI were critically reviewed, rigorously fact-checked, and substantially edited by the authors. The final manuscript, including its intellectual content, interpretations, and conclusions, is solely the responsibility of the authors, and the AI tool served exclusively as an auxiliary tool for literature organization and writing.

2. Soil Disinfection

Soil-borne nematode, fungal, and bacterial pathogens are diverse (

Table 1. Species Richness for Major Soil-borne Pathogens and Invertebrate Pests at Global or National Scales.

Category	Major Pathogen/Pest Types	References
Oomycetes and Fungi	Phytophthora, Verticillium, Rhizoctonia, etc. (>10,000 species)	[13]
Bacteria	Ralstonia solanacearum, soft rot bacteria, etc. (several thousand species)	[14]
Soil Protozoa	Parasitic (Apicomplexa), fungivorous, omnivorous (>100,000 species, 1700 described)	[15]
Nematodes	Root-knot nematodes, cyst nematodes, and other plant-parasitic types (25,000 species described)	[16]
Soil Insects	Beetle larvae, springtails (Collembola), etc. (tens of thousands of species)	[17]

), leading to a significant increase in the risk of crop yield reduction [12]. Therefore, soil disinfection has become a key measure to control such pathogens, prevent crop damage, and maintain target yields.

Currently, soil disinfection primarily relies on chemical and biological control methods [18,19,20,21,22,23]. Common pesticides include Metha sodium, Calcium cyanamide, Dazomet, Lime nitrogen and their mixed formulations [24,25,26,27]. In recent years, due to growing concerns about the potential hazards of excessive chemical agent use to human health, countries such as the United States, Australia, and the United Kingdom have imposed restrictions on the use of these fumigants [28,29,30,31,32]. Subsequently, the industry has successively developed alternative chemical agents, such as 1,3-dichloropropene and dimethyl sulfide [33,34,35,36,37,38]. However, chemical fumigation technology still has significant drawbacks: on the one hand, while eliminating pathogenic bacteria, it contaminates arable land and endangers human health [39]; on the other hand, after chemical fumigation, the soil requires prolonged airing before it can be replanted, which significantly reduces the sustainable production efficiency of agricultural soil [9]. While chemical pesticides hold irreplaceable advantages in terms of rapid response and emergency control, their fundamental limitations compared to physical control technologies lie in their high environmental costs, significant ecological disruption, and poor long-term sustainability. Although certain physical control methods face efficiency constraints, their environmentally benign, safe, and residue-free characteristics better align with the requirements of sustainable modern agriculture. Future development should prioritize an integrated management system establishing physical and biological controls as the foundation, with chemical interventions serving as targeted supplements.

Table 2. Soil-borne Disease Management Technologies [45].

Soil-Borne Disease Management
Agriculture Control	Biological Control	Physical Control	Chemical Control	Integrated Management
Resistant varieties and grafting	Biofumigation	Solarization	allyl isothiocyanate, AITC	Solarization-chemical
Blocking Pathogen Transmission	Anaerobic Soil Disinfestation	Soil flame disinfection	dimethyl disulfide, DMDS	Fumigant–non-chemical rotation
Deep plowing	Biocontrol formulations	Microwave sterilization	ethanedinitrile, EDN	Fumigant–contact pesticide
Crop rotation		Radio Frequency Disinfection	ethylicin	Fumigant–contact fungicide
Soilless cultivation		Soil Electrolytic Disinfection		Fumigant–Grafting Combined

systematically outlines the major control techniques for soil-borne diseases, covering five categories and their specific application methods, reflecting the current multi-dimensional strategies for integrated agricultural disease management. Soil temperature, moisture, pH, and organic matter critically regulate soil-borne disease dynamics. Soil temperature governs pathogen survival thresholds: Fusarium oxysporum actively infects at 20–30 °C, while 50–60 °C treatment eliminates >90% of pathogens within 30 min; conversely, sub-20 °C conditions promote localized disease outbreaks [40]. Moisture regulates disease progression through oxygen availability. At ≥98% relative humidity, spore germination increases significantly, whereas dry conditions suppress it by 37.1%. Post-rainfall disease exacerbation in warm, humid regions [41] underscores the effectiveness of rain-sheltered cultivation and subsurface drip irrigation as containment measures. Soil pH modulates microbial community structure; at pH < 5.0, beneficial bacteria decline by 30–50%, while Fusarium oxysporum spore germination increases 2–3-fold [42]. Alkaline amendments such as lime or biochar elevate pH and significantly reduce cucumber Fusarium wilt incidence [43]. Organic matter below 1.2% reduces root defense enzyme activity by 41%, weakening resistance to sheath blight, whereas corn straw compost application concurrently optimizes pH, organic matter, and microbial communities, yielding dual benefits of disease suppression and 8% yield enhancement [44]. These factors interact synergistically; integrated strategies combining high-temperature solarization, moisture regulation, pH amendment, and organic matter enhancement offer a quantifiable, sustainable framework for soil-borne disease management.

3. Soil Flame Disinfection Technology

Soil flame disinfection technology is one of the important techniques for soil remediation and improvement. Its core principle is to generate a high-temperature flame up to 800~1000 °C through the combustion of fuel in a short period of time [10]. This causes the soil temperature to reach the lethal threshold for pests, diseases, and weeds. According to the irreversible denaturation of proteins within living organisms caused by high temperature, the cell structure and physiological functions of the organisms are destroyed, ultimately achieving the effect of sterilization and pest control [46,47,48]. The prominent advantage of this technology lies in its environmental friendliness: on the one hand, no pesticides are needed in the sterilization process, which avoids the introduction of chemical agents from the source; on the other hand, high temperature can decompose some pesticide residues in the soil, achieving “no residue” treatment [49,50,51].

3.1. Research on the Impact of Flame on Soil Nutrients

Research on the impact of fire on soil nutrients has achieved certain results, but the research scope mainly focuses on the effects of surface flame combustion on the soil. The exploration of the underlying mechanisms and complex regulatory factors is still insufficient. In fact, the impact of fire on soil nutrients is not a simple promoting or inhibiting effect, but rather a complex dynamic process driven by multiple factors such as fire intensity, ecosystem type, and the recovery time after burning.

Specifically, fire intensity and the recovery time after burning are the key variables that regulate changes in soil nutrients. Song et al. [52] found that the soil organic matter (SOM) content in burned plots was significantly higher than that in undisturbed plots. The core mechanism lies in the fact that ash produced by fire can provide abundant soluble nutrients such as potassium (K) and calcium (Ca), while the high-temperature environment can accelerate litter decomposition, supplementing the accumulation of soil organic matter. Li et al. [53] conducted in a grassland ecosystem that revealed complex mechanisms and spatiotemporal dynamics governing soil carbon changes in response to flame burning. Their findings demonstrate that the impact of grassland biomass burning on soil carbon content depends simultaneously on the fire characteristics, frequency, and intensity. Vertically, soil organic carbon (SOC) exhibited a clear decreasing trend from the surface downward through the 0–50 cm soil layer. Temporally, the soil carbon pool showed significant variations with different post-fire recovery periods: in newly burned sites, SOC content across all soil layers was significantly higher than in unburned areas, primarily due to the initial enhancement of soil biological activity promoted by low-intensity burning. In contrast, several years after the fire, SOC in deeper soil layers was significantly greater than in unburned sites, attributable to the long-term accumulation of black carbon and nutrient replenishment from vegetation recovery. This series of changes indicates that the influence of flame on soil carbon exhibits a distinct threshold effect and strong time-dependent characteristics. In addition to fire intensity and recovery time, differences in ecosystem types also significantly alter the effects of fire disturbance on soil nutrients, highlighting the necessity of optimizing fire management parameters according to local conditions. Zhou et al. [54] analyzed the changes in soil physical and chemical properties after different-length-time burning of pine artificial forests and concluded that low-intensity planned burning for no more than 60 min is beneficial to improving soil nutrients. After analyzing the species composition, diversity, and aboveground biomass of plant communities in winter-burned and unburned areas of typical grasslands on the Loess Plateau, Zhao et al. [55] found that burning significantly reduced the number of perennial grass species, affecting the species composition and structural type of the communities. However, it notably increased the contents of soil organic carbon and total nitrogen in the 0–10 cm soil layer, thereby enhancing the topsoil fertility of the grasslands. Notably, among all regulatory factors, fire intensity often plays a decisive role, and high-intensity fire usually causes irreversible loss of soil carbon pools. Liu et al. [56] studied that high-intensity flames would reduce the organic carbon in pine forest soil by 25.3%. Yang et al. [57] conducted fire disturbance experiments on grassland systems and monitored soil property changes over 90 days. The results indicated that fire disturbance increased the topsoil temperature, pH value, and available nitrogen content of the grasslands, while decreasing soil water content, organic carbon, available potassium, phosphorus content, and microbial biomass; the contents of total phosphorus, total potassium, and available phosphorus showed almost no change. Zhou et al. [58] studied the changes in soil available potassium content in Larix gmelinii forests under different intensity fire disturbances. Their research aimed to analyze the soil available potassium nutrient level in the early recovery stage of burned areas, providing a reference for the regulation and management of soil potassium nutrients in forestlands.

In summary, the impact of fire disturbance on soil nutrients is the result of the interaction of multiple factors, including fire intensity, ecosystem type, and recovery time. The specific response characteristics and key influencing factors of different ecosystems are systematically summarized in

Table 3. Effects of flame combustion on Soil Properties Across Different Ecosystems.

Ecosystem	Flame Intensity/Duration	Soil Organic Matter	Nitrogen Content	Phosphorus Content	Potassium Content	Microbial Biomass	Source
Chinese Fir Plantation	Low intensity, ≤60 min	Increased	Initial increase	Initial decrease, subsequent increase	No significant effect	–	[54]
Typical Grassland	Winter burning	Increased (0–10 cm)	Increased (0–10 cm)	–	–	–	[55]
Chinese Pine Forest	High intensity	Decreased by 25.3%	–	–	–	–	[56]
Leymus chinensis Grassland	Simulated burning	Decreased	Available N increased	No significant change	Available K decreased	Decreased	[57]
Larix gmelinii forest	Moderate-severe burning	–	–	–	Significantly increased	–	[58]

Note: “–” indicates no data reported in the original study. All measurements were conducted in the 0–20 cm soil layer unless otherwise specified.

.

These differential responses across ecosystems, as synthesized in Table 3, highlight the context-dependent nature of fire impacts on soil nutrient dynamics. The data indicate a general pattern wherein initial increases in total and available nitrogen—attributed to the incorporation of nitrogen from combusted biomass into the soil via thermal processes—are often followed by a decline as vegetation re-establishes and immobilizes nitrogen. In later stages, elevated soil pH may enhance nitrogen fixation, leading to a recovery or even net gain in soil nitrogen. In contrast, total phosphorus, total potassium, and available potassium typically show minimal response to burning, suggesting their stability in mineral forms across different fire regimes. Available phosphorus, however, often exhibits a short-term decrease, likely due to adsorption onto newly formed mineral surfaces or microbial immobilization.

Overall, these patterns suggest that low-intensity, short-duration flame exposure can generally improve soil nutrient availability in most ecosystems. However, high-intensity treatments carry a significant risk of organic carbon loss. Therefore, optimizing flame parameters according to specific ecological contexts is essential for achieving beneficial outcomes.

3.2. Research on Flame Weed Control

The efficacy of flame weeding is fundamentally determined by the physiological responses and heat tolerance mechanisms of plants [59]. When exposed to intense, rapid heat from a flame, plant cells are damaged primarily through the rupture of cell membranes and the denaturation of proteins. Key factors influencing a plant’s susceptibility include its morphological and physiological traits. Species with thin cuticles, broad and tender leaves, and high leaf moisture content are generally more sensitive, as the heat rapidly vaporizes internal water, causing cells to burst. Conversely, weeds with adaptations such as thicker cuticles, waxy leaf surfaces, dense pubescence, or a prostrate growth habit may exhibit greater tolerance [60]. These traits can insulate meristematic tissues or reflect/dissipate heat. Furthermore, seed dormancy and burial depth are critical for survival. Seeds buried deeper in the soil are protected from the brief, high-temperature pulse at the surface, allowing them to germinate later. This differential tolerance between weed species and between weeds and crops forms the biological basis for effective flame weeding.

Regarding the sensitivity of weeds to flame, Guo et al. [61] found that the sensitivity of weeds to flames decreases with the increase in leaf age. Ascard [62] conducted field experiments on flame weed control for natural weeds at different growth stages. He established a dose–response model using the logistic model and compared the sensitivity of weeds across different species and growth stages, confirming that plant size has a major impact on the required propane dosage. Ulloa et al. [63] evaluated the response of four weed species to propane combustion at three different growth stages using six propane dosages. The results showed that the response of weeds to propane combustion varies with species, growth stage, and propane dosage. Due to the significant differences in propane dosage requirements for weeds of different species and growth stages, the optimal flame weed control scheme must be determined through dose–response models. Zhao [64] studied the heat transfer temperature of soil during flame combustion and the germination rate of weed seeds by adjusting the height of the flame nozzle above the ground and the burial depth of weed seeds. The analysis revealed that the heat transfer temperature of the surface soil responds rapidly and cools down quickly, while the temperature transfer in the deeper soil (within the detection range) is slower and the cooling rate is also slower than that of the surface layer. The weed control rate for surface seeds reached over 83%, that for seeds buried at 1 mm depth exceeded 63.5%, and that for seeds buried at 2 mm depth was more than 58%. Ultimately, it was concluded that the weed-killing effect of flame is related to the burial depth of weed seeds.

Regarding differences in flame tolerance across weed species, Sivesind [65] studied the response of five common weeds (including Rumex japonicus and Capsella bursa-pastoris) to cross-flaming. Dose–response curves were generated based on species and growth stages, leading to the conclusion that different weeds require different doses of the flaming agent. Ulloa et al. [66] applied five propane doses to control weeds in organic corn fields. Their study showed that corn at the 5-leaf stage was most tolerant to flame, while corn at the 2-leaf stage was the most sensitive—exhibiting the most significant visual crop damage and yield loss. Carrington [67] measured soil temperatures at different depths and micro-sites during sand pine thicket fires. It was found that small-scale spatial variations in temperature at the soil surface are crucial for the survival and subsequent growth of weed seeds. Sivesind et al. [68] used flame to remove weeds in onion cultivation. They observed excellent weed control efficacy, while flame had minimal impacts on onion maturity and quality (including pungency and soluble solids content). Lara et al. [69] conducted field experiments to investigate the effects of different flaming doses and durations on weed control and garlic yield. Garlic showed reasonable tolerance to flame, withstanding up to three flaming treatments. The experiment also emphasized the need for integrated weed control strategies, suggesting that organic garlic growers could use flame as a replacement for manual weeding.

To balance weed control efficacy and crop safety, many researchers have identified key operational parameters for flame weed control. Sivesind et al. [68] found that with increasing propane doses and flame treatment frequencies, the weed density in all flame-treated areas decreased by 50% compared to the untreated control areas. Rajkovic et al. [70] determined the optimal flaming direction of the flame applicator by quantifying the flame temperature distribution of the burner at crosswise, backward, and parallel positions across different heights of the soybean canopy (i.e., the distance from the soil surface). Flame temperatures corresponding to the three burner directions were measured under 7 propane dosages (20–100 kg/ha) and 8 distinct canopy heights (0–18 cm above the soil surface). For all three burner directions, higher flame temperatures were recorded at lower canopy heights (<6 cm), while the flame temperatures gradually decreased as the canopy height increased (6–18 cm). The temperature ranges measured in the experiment were 33–234 °C for crosswise flaming, 29–269 °C for backward flaming, and 23–155 °C for parallel flaming. Backward flaming also generated flame temperatures exceeding 100 °C, and required a lower propane dosage (27 kg/hm²) compared to crosswise flaming (40 kg/hm²) and parallel flaming (50 kg/hm²). Among all tested parameters, parallel and crosswise flaming exerted more favorable effects on soybeans than backward flaming; however, crosswise flaming is typically employed for controlling weeds between crop rows. Taylor et al. [71] identified the optimal time of day for propane flaming, aiming to maximize weed suppression while minimizing damage to corn crops. Lara et al. [69] emphasized that flame technology necessitates adjusting the timing of intervention based on weather conditions and the degree of weed infestation, as well as optimizing technical parameters such as LPG pressure and tractor travel speed. Compared with traditional weeding methods, flame weed control demonstrates advantages primarily in terms of efficiency and economics. Upadhyay et al. [72] conducted a comparative evaluation of flame weed control and traditional weeding methods, focusing on aspects including weed control efficacy, operation time, energy consumption, and operational cost. The results indicated that, in contrast to manual weeding, flame weed control reduced costs by 50.42% and increased speed by 94.82%. Additionally, flame weed control can serve as a core technology in organic farming (e.g., replacing manual weeding in garlic fields) and exerts no significant negative impacts on the yield and quality of certain crops.

The differences in responses to flame between weeds and crops serve as the foundation for the application of flame weed control technology. Operational factors in the flame weeding process—such as appropriate flaming dosage, burner direction, and timing—are essential guarantees for its efficacy. Future research is required to further advance flame weed control technology. Key areas for improvement include exploring approaches to reduce costs, adapting the technology to different crop types and planting scenarios, refining flaming parameters, and minimizing crop damage while ensuring effective weed control. These efforts will enable the technology to better serve agricultural production practices.

3.3. Research on the Effects of Flame (Temperature) on Pests

Temperature is a critical factor influencing the reproduction, occurrence, and distribution of pests, microorganisms, and other organisms. The core principle of pest control via flame disinfection lies in generating high temperatures exceeding the tolerance limit of pests and pathogenic organisms within a short period, thereby inhibiting their growth and development or directly causing mortality. Clarifying the temperature tolerance range of different pests constitutes the foundation for the precise application of flame disinfection technology [73]. The critical lethal temperature–time thresholds are summarized in Table 4.

Under heat stress, insects maintain proteostasis by upregulating heat shock protein (HSP) families (HSP70, HSP90, and small HSPs), which serve as molecular chaperones to prevent aggregation of denatured proteins and facilitate refolding of misfolded proteins. Studies have demonstrated that in the brown planthopper (Nilaparvata lugens), HSP70 expression exhibits a dose-dependent increase with rising temperature, showing significant upregulation after 2 h of treatment at 35 °C and thereby enhancing thermotolerance [10]. During diapause, HSP70 in the cotton bollworm (Helicoverpa armigera) similarly responds to heat shock, protecting developmental progression. In Spodoptera litura, sHSP21 expression surges following heat shock at 40 °C, positively correlating with larval survival rates. Likewise, in the flesh fly (Sarcophaga crassipalpis), despite being downregulated during pupal diapause, sHSP21 remains responsive to heat shock, modulating stress protection during metamorphosis [74]. As high-temperature stress rapidly depletes insect energy reserves, protective compatible osmolytes are accumulated. In Drosophila melanogaster, trehalose synthase activity increases threefold following heat shock at 40 °C, maintaining hemolymph osmotic pressure and preventing cellular dehydration [75].

Table 4. Lethal Temperature and Exposure Time Thresholds for Major Soil Pests.

Type	Target Organism	Lethal Temperature Threshold	Critical Exposure Time	Source
Soil pests	Delia antigua (Meigen)	>40 °C	1.3–1.4 h	[76,77]
	Grubs	>50 °C	Egg and larval mortality within 10 min	[78]
	Agrotis ipsilon	>35 °C	5 min	[79,80]

Table 4. Lethal Temperature and Exposure Time Thresholds for Major Soil Pests.

Type	Target Organism	Lethal Temperature Threshold	Critical Exposure Time	Source
Soil pests	Delia antigua (Meigen)	>40 °C	1.3–1.4 h	[76,77]
	Grubs	>50 °C	Egg and larval mortality within 10 min	[78]
	Agrotis ipsilon	>35 °C	5 min	[79,80]

The data presented in Table 4 offer quantitative benchmarks for thermal-disinfection protocols; consequently, flame parameters must be dynamically tuned to the target pest in operational practice. This section reviews the studies on the response patterns of several typical soil-dwelling pests to fire flames (or temperature).

3.3.1. Delia antigua (Meigen)

Mei et al. [76] investigated the biological characteristics of Bradysia odoriphaga under four temperature gradients: 15 °C, 20 °C, 25 °C, and 30 °C. The results indicated that Bradysia odoriphaga could complete its growth, development, and reproduction within the range of 15–30 °C, with 20–25 °C being the optimal temperature for its growth. At this temperature range, Bradysia odoriphaga exhibited high survival rate, strong fecundity, and a relatively short generation cycle [81]. Wang et al. [77] studied the occurrence, damage patterns, and green control technologies of chive Delia antigua (Meigen). Leveraging the characteristic that eggs, larvae, pupae, and adults of chive Delia antigua (Meigen) cannot survive at temperatures above 40 °C, they adopted a practice of covering the soil with plastic film in the morning and removing it in the evening. This approach raised the temperature inside the film above 40 °C, achieving a maggot mortality rate of 98%. The research team led by Zhang [82] further confirmed the heat intolerance of Bradysia odoriphaga, demonstrating that covering the ground with a layer of transparent, heat-preserving, anti-fog film to increase soil temperature could effectively kill the pest. Shen et al. [83] conducted a study on garlic root maggots, revealing that their generation cycle lasts 46 days (3 days for eggs, 17 days for larvae, 20 days for pupae, and 6 days for adults). The survival rate of garlic Delia antigua (Meigen) reached 95–100% under conditions of 16–21 °C and relative humidity of 30.3–52.4% (temperature–humidity coefficient: 1.44–3.44). However, high temperatures (exceeding their tolerance threshold) significantly reduced their survival rate.

3.3.2. Grub

The grub larvae are white in color and have strong concealment ability. They prefer to live in the soil and are the main underground pests in garlic cultivation [84]. Garlic plants damaged by grubs have their root systems rot, unable to absorb water and nutrients, resulting in wilting leaves and yellowing plants. Chen et al. [78] showed that the damage behavior of grubs exhibits regularity with changes in soil temperature: grubs move up to the plow layer to cause damage when soil temperature reaches 10 °C, become most active at 13–18 °C, and move to deeper soil layers when the temperature exceeds 23 °C. This characteristic provides a reference for determining the timing of flame disinfection—if soil temperature can be raised to a range unsuitable for grubs via high temperature during their active period (13–18 °C), their damage can be effectively inhibited.

3.3.3. Agrotis ipsilon

Yang et al. [79] studied the effects of different temperatures on the development, survival, reproduction, population parameters, and population trend index of the Agrotis ipsilon. They determined that the optimal temperature for the small ground beetle is 21–25 °C. When the temperature exceeds 31 °C, the mortality rate of each life stage significantly increases. At 35 °C, a large number of eggs, larvae, and pupae die, indicating that high temperatures have a significant inhibitory effect on the growth and development of the small ground beetle. Xiang et al. [80] examined the growth, development, and reproduction of the black cutworm under seven temperatures: 16 °C, 19 °C, 22 °C, 25 °C, 28 °C, 31 °C and 34 °C. The results showed that the optimal temperature for the growth, development, and reproduction of the black cutworm population is around 25 °C. As temperature increases, the growth rate of the Agrotis ipsilon accelerates and the developmental duration shortens; however, when the temperature reaches 31 °C, the growth rate of eggs, larvae, and pupae begins to slow down. Additionally, the female ratio of the Agrotis ipsilon population decreases with increasing temperature. Under both low and high temperature conditions, the adult lifespan of the Agrotis ipsilon shortens, while its survival rate and fecundity decrease. This implies that raising the ambient temperature above 31 °C via flame can effectively control the population size of the Agrotis ipsilon.

The temperature tolerance thresholds of major pests such as Delia antigua (Meigen), cutworms, and white grubs differ, and the ranges of their optimal growth temperatures and lethal temperatures have been basically clarified, providing theoretical support for the precise application of flame disinfection technology. However, further research is needed on details such as the differences in temperature sensitivity of pests at different developmental stages, so as to enhance the targeting and efficiency of the technology.

3.4. Research on the Effects of Flame Disinfection on Pathogens

The mechanism and application value of soil flame disinfection on soil-borne pathogens have been clearly verified. Pathogenic microorganisms such as Fusarium and Root-knot nematodes exist in the soil, and they are prone to causing soil-borne diseases, including fusarium wilt and root rot [11]. The use of single-agent spraying or fumigation not only makes it difficult to achieve the desired control effect but also induces the development of drug resistance in pathogens [45,81,82]. As a physical disinfection method that uses high temperature to kill pathogens, flame disinfection leverages instantaneous high temperature to denature macromolecular substances (e.g., proteins and nucleic acids) in pathogens, destroy their structure and function, and thereby achieve inactivation. Compared with traditional disinfection methods, it has the advantages of high efficiency and no chemical residues [83].

Existing studies have confirmed that flame disinfection exerts a significant inhibitory effect on a variety of pathogenic microorganisms. Mao et al. [84] conducted field experiments to evaluate the control efficacy of soil flame disinfection against soil-borne nematodes, fungal, and bacterial pathogens. The results showed that soil flame disinfection could reduce the total number of nematodes by approximately 95%, and completely control cryptic nematodes in the soil. Its control effects on Fusarium oxysporum, Phytophthora spp., and the tomato wilt pathogen (Fusarium) reached over 44%, 47%, and 67%, respectively. Yang et al. [85] verified the disinfection effect of flame on weeds, nematodes, and fungi by designing a flame disinfection device, and found that flame disinfection not only kills weeds, nematodes, and fungi but also indirectly promotes crop growth. This article summarizes the lethal temperatures and exposure time thresholds for some major pathogens, as shown in

Table 5. Lethal Temperature and Exposure Time Thresholds for Major Pathogens.

Type	Target Organism	Lethal Temperature Threshold	Critical Exposure Time	Source
Fungi	Fusarium	>60	30 min	[93]
	Rhizoctonia solani	50	10 min	[94]
	Pythium	50–55	10–30 min	[95]
	Phytophthora	30–35	30 min	[96]
Bacteria	Ralstonia solanacearum	52–53	10 min	[97]
	Agrobacterium tumefaciens	50	10 min	[98]
	Pectobacterium carotovorum	50–53	30 min	[99]
	Streptomyces scabies	50	30 min	[100]
Virus	Soit-borne wheat mosaic virus	60–65	30–60 min	[101]
	Tobacco mosaic virus	95	10 min	[102]
Parasite	Meloidogyne incognita	55	10 min	[103]
	Heterodera spp.	50	30–60 min	[90]

. Flame disinfection exerts potential effects on non-target organisms; however, these impacts are transient and reversible. Research indicates that bacteria capable of forming thermo-tolerant endospores, such as Bacillus and Clostridium, exhibit strong resistance to flame disinfection due to their robust outer structures and high lipid content [86]. Consequently, conventional flame treatment may be insufficient for their complete eradication, often requiring prolonged high-temperature exposure or chemical biocides for effective inactivation. In contrast, fungi such as Fusarium and Aspergillus demonstrate relatively higher sensitivity to elevated temperatures [87]. One study reported that heating pasture soil to 500 °C significantly reduced parasite survival rates [88]. Meanwhile, within five months post-treatment, both the biophysical environment of the soil and the abundance and diversity of arthropods recovered to levels comparable to unburned areas [89]. Flame disinfection utilizing instantaneous high temperatures (50–70 °C) effectively eliminates soil-borne pathogens, insect eggs, and similar threats [90]. Furthermore, analogous thermal or fumigation strategies have been shown to significantly suppress specific pathogenic fungi and reshape bacterial community structures [91]. Similar to chemical fumigants, which can alter microbial communities and elemental cycling, flame disinfection may induce comparable short-term disturbances. Nevertheless, evidence suggests that soil ecosystems possess considerable biological resilience [92]. Moreover, such perturbations may create opportunities for beneficial microorganisms to thrive, potentially leading to the establishment of a healthier soil micro-ecology.

Compared with chemical control, flame disinfection—relying on the mechanism of pathogen inactivation via high temperature—has advantages such as avoiding drug resistance and chemical residues, achieving thorough disinfection effects, and saving labor and time. However, systematic conclusions have not yet been formed regarding details such as the specific inactivation temperature thresholds for different pathogens and the impact of the disinfection process on the soil environmental microbial community.

3.5. Research on the Effects of Flame on Soil Microbial Communities

High-intensity fires may exert a transient inhibitory effect on certain microbial taxa; how-ever, a substantial body of research demonstrates that moderate flame exposure and temperature variations can optimize soil microbial community structure, enhance their eco-logical functions, and facilitate ecosystem recovery and stability. Fire induces profound structural reorganization of soil microbial communities by altering soil physicochemical properties and resource availability. This restructuring is not a random process but follows specific principles of ecological selection, ultimately leading to functional optimization of the microbial community to adapt to new environmental conditions. Research has indicated that the enrichment of specific microbial taxa in post-fire soils is closely associated with changes in multiple environmental factors, including increased soil pH, short-term elevation of available nutrients, and alterations in organic matter composition [104]. The response of microbial communities to fire is manifested not only through compositional changes but, more importantly, through enhanced functional redundancy and niche complementarity. Distinct microbial taxa assume unique ecological roles in the post-fire environment, collectively facilitating ecosystem recovery through synergistic interactions [105]. Following fire events, Proteobacteria and Actinobacteria emerge as dominant groups within the bacterial community [106]. Certain taxa within Proteobacteria possess nitrogen-fixing capabilities, which is particularly crucial in post-fire nitrogen-limited eco-systems, helping to alleviate nitrogen constraints on ecosystem recovery [104]. In contrast to bacterial communities, soil fungal communities exhibit distinct differential response and delayed recovery following fire disturbance. This disparity may stem from fundamental differences in biological characteristics and ecological strategies between fungi and bacteria. Fungi typically possess more complex mycelial networks and longer life cycles, characteristics that necessitate extended recovery periods after fire disturbance [107]. Nine years postfire, fungal communities demonstrate a higher proportion of saprotrophic fungi and a lower proportion of pathogenic fungi [108]. This shift holds significant implications for eco-system functional recovery, as saprotrophic fungi play crucial roles in organic matter de-composition and nutrient cycling.

Changes in soil microbial community structure exert profound impacts on ecosystem processes. The microbial community following flame disturbance can execute multiple key ecological functions more effectively, thereby accelerating post-fire ecosystem recovery [109]. On one hand, shifts in the microbial community directly influence the rate and pathways of soil nutrient cycling [110]. For instance, the enriched Proteobacteria and Actinobacteria can accelerate the decomposition of post-fire organic residues, releasing plant-available nutrients. On the other hand, alterations in microbial community composition also affect soil aggregate structure and pore size distribution, subsequently modifying soil water retention capacity and aeration [104]. Research has found that microbial communities in unburned areas exhibit fewer facilitative interactions compared to those in fire-affected areas [108]. Microorganisms influence fundamental ecosystem functions through various path-ways, including participating in biogeochemical cycles, affecting plant–soil feedbacks, and regulating soil greenhouse gas emissions. The optimized microbial community formed after a fire is not only better adapted to the post-fire environmental conditions but also creates a favorable soil environment for the recovery of plant communities, thereby accelerating the restoration process of the entire ecosystem [109]. Whereas conventional perspectives often emphasize the negative impacts of fire on microbial diversity, a growing body of evidence suggests that moderate fire disturbance may actually promote an increase in soil microbial diversity, particularly over medium to long-term scales. This phenomenon stems from the dual mechanisms of fire’s effect on microbial communities: (1) Fire-induced high temperatures directly eliminate heat-sensitive microbial taxa. (2) Post-fire environmental changes create conditions for the proliferation of heat-tolerant and fast-growing taxa, resulting in new ecological niches and richer species assemblages [111]. The coexistence of various resource types in post-fire soil—including partially combusted organic matter, charred particles, and mineral components—provides survival opportunities for microbial taxa with different resource requirements [112,113].

The impacts of fire and associated temperature changes on soil microbial communi-ties are multifaceted and complex, encompassing both transient inhibitory effects and long-term positive influences. Moderate fire disturbance exerts beneficial effects on soil ecosystems through multiple pathways: optimizing microbial community structure, enhancing diversity, strengthening functional capacity, and facilitating ecosystem recovery. These positive impacts are primarily manifested in: (1) Selective enrichment of microbial taxa with specific functional traits, leading to optimized community structure; (2) In-creased microhabitat heterogeneity, thereby enhancing microbial diversity; (3) Reinforcement of microbial nutrient cycling functions and improvement of energy utilization efficiency; (4) Activation of the intrinsic resilience of microbial communities, promoting eco-system stability. A comprehensive understanding and utilization of these beneficial fire-temperature effects on soil microbial communities holds significant practical im-portance for ecosystem management and restoration.

3.6. Risks of Long-Term Continuous Use and the Necessity of Method Rotation

The core advantage of soil flame sterilization lies in its immediate effectiveness and absence of chemical residues. However, like other soil disinfection methods, this approach also faces ecological challenges, particularly when applied exclusively over the long term, as its adverse effects on soil ecosystems become increasingly apparent. Studies have shown that sustained application of high-intensity soil disinfection measures leads to a simplified soil microbial community structure, where functional microbial communities recover significantly more slowly than pathogenic microorganisms [114]. Particularly noteworthy is that beneficial microorganisms crucial to soil ecosystem health, such as arbuscular mycorrhizal fungi (AMF), are thermosensitive and exhibit prolonged recovery periods following sterilization [115]. In soils subjected to long-term continuous flame sterilization, this recovery process may be repeatedly disrupted, ultimately resulting in irreversible declines of beneficial microbial communities and consequently weakening the natural disease resistance capacity of the soil ecosystem. Soil sterilization also influences soil nutrient cycling processes. Microorganisms are the primary drivers of soil nutrient transformation, and changes in their community structure directly affect the biogeochemical cycling of key nutrients such as nitrogen and phosphorus [116]. Studies have found that the abundance of microbial functional genes involved in nutrient cycling is significantly altered in repeatedly sterilized soils, which may further affect crop nutrient use efficiency [117,118]. Furthermore, over-reliance on flame sterilization may lead to the development of pathogen resistance. Although flame sterilization operates through physical high-temperature action without involving chemical agents, repeated applications can select for microbial communities with thermal resistance, thereby diminishing sterilization efficacy.

Given the multiple risks associated with the long-term exclusive use of flame sterilization, implementing a rotation of multiple disinfection methods has become a crucial strategy for sustaining soil health. The core theoretical foundations of method rotation are threefold: (1) disinfection methods with distinct mechanisms of action exert differential impacts on soil ecosystems; (2) rotational application prevents the development of adaptation in specific pathogens; (3) it facilitates the preservation of diversity and resilience within soil microbial communities. Soil health management is fundamentally a dynamic balancing process rather than an indiscriminate pursuit of complete sterilization. Research demonstrates that effective control of soil-borne diseases should not rely on singular technologies but should instead employ integrated management strategies that leverage the strengths of physical, chemical, and biological methods while mitigating their respective limitations. Method rotation embodies this principle in practice—by alternating different sterilization approaches, it achieves effective disease control while simultaneously preserving the long-term health of soil ecosystems. Studies have reported that the combined use of soil solarization and flame sterilization reduced weed seedling emergence density by 83% compared to the control [119]. Research demonstrates that steam and flame weeding achieve 95% weed control with a residual effect lasting 3–4 weeks, and early-season application is recommended for optimal efficacy [120]. Flame sterilization can be combined with high-temperature solarization and microbial agents, demonstrating significant efficacy in pest and disease control in cucumber and pepper greenhouses, with dual applications outperforming a single treatment [121]. The PAMS approach to integrated pest management classifies both flame treatment and soil solarization as physical suppression measures, representing non-chemical control strategies that can be combined within the IPM framework. Implementing a soil disinfection method rotation strategy that integrates multiple techniques—including flame sterilization, chemical fumigation, biological control, and physical methods—can more effectively maintain soil health while controlling soil-borne diseases. This integrated approach addresses short-term disease control needs while simultaneously preserving the long-term health of soil ecosystems, thereby aligning with the trends of green agricultural development.

4. Research on Flame Disinfection Equipment and Precise Control Technology

4.1. Development of Flame Disinfection Devices

Common high-temperature flame disinfection machines include handheld, hand-pushed, and self-propelled types. These devices can effectively eliminate pathogenic bacteria in the soil surface layer; when combined with soil rotary tillage and crushing operations, they can also achieve a certain degree of deep-soil disinfection. In order to systematically contrast the performance gaps between Chinese and international apparatuses, the key specifications of representative devices are consolidated in

Table 6. Performance Comparison of Typical Chinese and International Soil Flame Sterilization Devices.

Category	Device Name	Fuel Type	Working Width (m)	Working Depth (cm)	Pest/Weed Control Efficiency (%)	Intelligence Level	Source
Chinese	Precision Rotary Flame Sterilization and Ridging Machine	Liquefied Petroleum Gas	1.2	22	82.9 (Pest)	L2	[122]
Chinese	Biomass Pellet Flame Sterilization Rotary Tiller	Biomass Pellets	1.0	18	85 (Pest/Weed)	L1	[123]
Chinese	Tea Garden High-Temperature Flame Weeding Device	Liquefied Petroleum Gas	0.6	5–8	80 (Weed)	L0	[124]
International	RHEA Automatic Cross-Combustion Weeder	Propane	1.8	10–12	90 (Weed)	L3	[125]
International	Stepanovic Parallel Torch System	Propane	2 × 0.3	5–10	88 (Weed)	L2	[126]
International	Kang Flame Weeder	Liquefied Petroleum Gas	Not specified	Not specified	–	L1	[127]

Note: Intelligence Level Definition: L0 = Manual operation, L1 = Basic automation (single function control), L2 = Semi-automatic (integrated operation), L3 = Fully automatic (autonomous navigation).

.

As demonstrated in Table 6, Chinese units show a distinct focus on multifunctional integration, while foreign systems exhibit notable strengths in intelligent control and energy efficiency. It is therefore recommended that future efforts prioritize the advancement of cross-technological integration. In the field of device development, researchers in China and abroad have achieved substantial results, with their work focusing on directions such as integrated operation, function optimization, and application scenario expansion.

Chinese equipment places greater emphasis on the design of the overall operational process. Qiu et al. [122] proposed an integrated operational process encompassing “straight-knife crushing—scraper soil casting—flame disinfection—ridging formation” and further developed an integrated machine for precision rotary tillage, flame-based soil disinfection, and ridging. This equipment incorporates core components such as a rotary tillage and soil-crushing unit, a ridging unit, a flame disinfection unit, and an electronic ignition system. Through systematic analysis of blade distribution and quantity, soil casting volume, and thermal load requirements, the key structural parameters were determined. This design enables the equipment to fulfill the operational demands of integrated rotary tillage, disinfection, and ridging. A schematic diagram illustrating the equipment structure is provided in Figure 1.

Weng et al. [123] organically integrated soil rotary tillage operation with soil flame disinfection technology, used biomass pellets as fuel, designed a biomass pellet-fueled flame disinfection rotary tiller, and conducted theoretical analysis on its main mechanisms. Yang [128] designed a new type of flame-pesticidal fine rotary tiller, integrating a fine rotary tiller and high-temperature flame disinfection. The rotary tillage depth reaches 20–25 cm, addressing the issue that traditional rotary tillers cannot meet the demand for deep soil tillage. In addition, some researchers have improved and optimized the overall device targeting specific structures. For instance, Chen [129] addressed the issues of greenhouse roof melting and the inability to till irregular and small-sized plots, which existed in the self-propelled precision rotary soil flame insecticidal machine, and improved the design to develop a flame micro-tiller. By optimizing the parameters of the weeding rotary blades and flame nozzles, the weeding efficacy was enhanced. Experimental verification demonstrated that the weeding rate of this improved micro-tiller reached over 95%, while the insecticidal rate exceeded 97.7%. Guan et al. [130] designed a weeder with the combined action of flame and steam to solve the problem of excessive weeds in the cultivation of Chinese medicinal materials. By modeling its relevant key components, simulation verification showed that when the nozzle diameter was set to 5 cm, the flame injection diameter reached the maximum; the temperature effect was optimal when the actual treatment time was 25 s and the distance from weeds was 20 cm. He et al. [124] developed a hand-pushed high-temperature flame weeding device to address the difficulty of weed control in tea gardens. Experimental results indicated that this device exhibited a good control effect on broad-leaved weeds. Furthermore, the weed control effect was enhanced with the extension of treatment time; when the weed plants were relatively large, the flame output of the device needed to be increased accordingly.

The research conducted by foreign scholars has made significant breakthroughs in improving the performance of the devices and in the design of intelligent systems. Kang [127] evaluated the flame temperature distribution of several burners to select a suitable one, developed a flame weeder, and quantitatively assessed its weed control efficacy. The results showed that the liquefied petroleum gas (LPG) consumption was positively correlated with the weed control rate, and there were differences in the response to flame between different plant species as well as between plants of the same species at different growth stages. Frasconi et al. [125] designed and developed an automated machine for variable-rate cross-flaming application in cornfields. Equipped with a sensing system, this device enables selective and targeted cross-flaming among crops. During weeding operations, the ignition system of the burner completes ignition within 0.4 s, meeting the real-time requirement for weeding. Additionally, it is equipped with an automatic steering system, which can effectively avoid damage to corn plants. Stepanovic et al. [126] designed a device that placed two torches parallel to the crop rows, 15 cm away from the crop rows, at an angle of 30° downward. In addition, a cover was installed on the flame. This design not only directed the flame towards the soil surface, protecting the upper part of the crop canopy from heat damage, but also reduced energy consumption by up to 50% and increased the thermal exposure time of weeds, improving the weed control effect. The test results showed that the burning had almost no impact on the microbial biomass in the soil 5–10 mm deep. The soil flame disinfection machine designed by WANG et al. [24] can not only achieve disinfection but also increase crop height and yield.

Current research on flame disinfection equipment has advanced from single-function designs to integrated operation systems, which can incorporate operations such as rotary tillage and ridging. Foreign devices are more distinctive in terms of intelligence and performance optimization. In contrast, China started relatively late in the development of soil flame disinfection machinery. However, driven by strong market demand, significant progress has been made in recent years. China has complex terrain, requiring diverse soil flame disinfection machinery. It is necessary to further improve the disinfection effect of the devices on different soil depths, reduce energy consumption, and enhance their applicability in complex terrains.

4.2. Research on Precise Control Technology

The precision control of soil flame disinfection focuses on clarifying the law of soil heat transfer and optimizing the key structures of equipment. Currently, relevant research has made progress in two aspects: the construction of soil thermal parameter models and the optimization of equipment structural parameters.

Thermal conductivity is a fundamental parameter of soil heat transfer, which characterizes the soil’s ability to transfer heat energy. Its variation directly affects the efficiency of achieving target temperatures and depths during soil flame disinfection. Many researchers have studied this parameter to improve the predictive capability of thermal models. Xiong [131] compared the measured values of thermal conductivity of 5 soil types with the calculated values from 4 thermal conductivity models (including Campbell and Johansen models), and introduced a parameter F related to soil texture to improve the Campbell model. The improved model has higher prediction accuracy and can also be used to calculate the thermal conductivity of soils in other regions. Duan [132] revealed the basic laws of thermal conductivity, specific heat capacity, and thermal diffusivity varying with parameters such as moisture content, porosity, and permeability coefficient, and fitted the calculation formulas for thermal conductivity and specific heat capacity. Zhao [64] established a soil heat transfer model based on the coupling of the discrete element method (DEM) and computational fluid dynamics (CFD) (i.e., DEM-CFD coupled model). Using the coupling of Fluent software and EDEM software, the relevant model was established for numerical simulation. The results showed that there was a linear relationship between the height of the flame nozzle above the ground and the influence range and radius of soil heat transfer, and the maximum temperature appeared at the position where the nozzle vertically contacted the soil surface layer. In order to better highlight the significance of parameters such as soil thermal conductivity, specific heat capacity and thermal diffusivity, we have summarized the temperature and depth ranges required for typical disinfection targets, as shown in

Table 7. The temperature and depth range required for typical disinfection targets.

Disinfection Target	Target Temperature	Depth Range	Exposure Time	Conditions
Pathogen	55–70 °C	0–20 cm	10 min	A sufficient heat flux and action time are required.
Weed	60–80 °C	0–5 cm	5 min	The heat is concentrated on the surface; the required temperature is high but the duration is relatively short.
Pest	>55 °C	0–15 cm	8 min	Balancing the depth of heat penetration and the duration of temperature maintenance

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In terms of key structure optimization, the optimal design of the key parts of precision control can improve operation efficiency and reduce costs. Bu [133] carried out the design research of the flame weeding mechanism on the basis of the rotary tillage, weeding and soil covering machine, and optimized the design of the key structural parts of the flame weeder. The structure of the flame nozzle was optimized using Fluent simulation software, and it was determined that the optimal effect was achieved when the flame nozzle had a diameter of 16 mm and an arrangement spacing of 128 mm. By calculating the thermal radiation of the flame nozzle to the edge area, the flame parameters of the nozzle were controlled so that the heated radius formed by the flame on the soil surface was not less than 0.03 m, achieving a good treatment effect.

Precision control is an important part of evaluating the effects of flame disinfection technology, such as disinfection efficacy, cost consumption, and ecological safety. It requires the dynamic adjustment of heat transfer models based on different soil physical and chemical properties, as well as further collaborative optimization between equipment structure design and soil heat transfer laws.

5. Future Development Prospects

Soil flame disinfection equipment, characterized by high efficiency, environmental friendliness, and adaptability to organic agriculture, will enter a period of rapid growth in the next decade, driven by both policy support and market demand. The future development prospects of soil flame disinfection mechanisms and equipment precision control technology show multi-dimensional breakthrough potential. Its core lies in the in-depth advancement of the scientific mechanism of high-temperature physical disinfection and the precise upgrading of intelligent control technology. This section outlines the main development prospects by focusing on technological innovation, intelligent precise control, and the current gaps in key research.

(1)

Technological Innovation and Precision Control

Refined Analysis of High-Temperature Inactivation Mechanisms: Flame disinfection destroys the protein structure and DNA strands of pathogenic microorganisms by exposing them to high temperatures (approximately 1000 °C) for 2–3 s. Future research will further clarify the lethal temperature thresholds and thermal response differences in different pathogenic bacteria. The mechanism of high temperatures’ impact on soil organic matter will become a research focus. It is necessary to determine how to reduce the excessive decomposition of soil organic matter by controlling parameters such as flame intensity and action depth while killing pathogens. Through optimizing flame parameters, the dual goal of “pathogen elimination and fertilizer preservation” will be achieved.

(2)

Advanced Modeling and Real-Time Monitoring for Precision Control

Research on the Distribution Law of Heat Field in Soil Disinfected by Flame: Precision control relies on the accurate prediction and dynamic management of soil thermal fields. This involves integrating heat transfer theory with porous media models to develop standardized, reliable soil thermal models that account for texture, moisture, and organic matter. Currently, there is a lack of standardized soil heat models that are widely applicable. In the future, research can integrate heat transfer theory and porous media theory to investigate the distribution law of soil heat fields. On this basis, a coupled model of soil heat conduction and phase change can be established to analyze the differences in thermal response among soils with different textures, such as sandy soil and clay soil. Numerical simulation can be used to predict the temperature field distribution under different soil types, which provides a theoretical basis for the optimization of flame parameters. The research technical route is shown in Figure 2.

Multi-Sensor Fusion-Based Real-Time Monitoring System: Technologies such as infrared thermal imaging, soil temperature and humidity monitoring, and gas composition detection can be integrated to construct a three-dimensional “flame-soil-environment” monitoring network. In the future, hyperspectral imaging technology can be applied to accurately identify the distribution areas and contents of residual pesticides in soil. Based on this information, parameters including flame intensity and action duration can be dynamically adjusted, thereby achieving “pollution-targeted disinfection”.

AI-Driven Parameter Optimization Algorithm: Building upon foundational model studies, the integration of multi-sensor fusion and artificial intelligence (AI) will be critical. AI algorithms—particularly machine learning and reinforcement learning—can process these data streams to dynamically map relationships between flame parameters (e.g., temperature, velocity) and soil properties. This capability enables autonomous equipment adjustments; for instance, flame intensity can be regulated based on real-time soil moisture readings to ensure consistent treatment efficacy while optimizing energy consumption efficiency.

(3)

Standardization of Soil Flame Disinfection Technology

Standardizing soil flame disinfection technology is critical for standardizing its application and ensuring treatment efficacy. We propose that future research focus on three core parameters: First, temperature uniformity: Establish quantitative standards for soil profile thermal dosage, and achieve precise control via multi-probe real-time temperature measurement and CFD (Computational Fluid Dynamics) flow field optimization. Second, fuel efficiency: Define energy efficiency benchmarks for fuel consumption per unit area, and develop adaptive combustion control systems and high-efficiency burners to reduce energy use. Third, automated integration: For instance, integrate flame disinfection devices with autonomous navigation to enable variable-rate operation (based on soil information perception) and full-coverage precise path planning. Standardizing and optimizing these core parameters will significantly enhance the reliability, economic viability, and environmental adaptability of soil flame disinfection technology, making it a more competitive solution for green production in protected agriculture.

(4)

Specific Research Gaps

Standardized Thermal Models: There is an urgent need for universally applicable, validated models to predict heat propagation in different soil types.

Microbial Recovery Dynamics: Long-term studies are required to understand the recovery trajectories of distinct functional microbial communities post-treatment.

Life Cycle Assessment (LCA): Comprehensive environmental and economic LCA comparing flame disinfection with other methods is currently lacking, yet it is critical for evaluating its true sustainability.

Clean Energy Integration: Replace traditional liquefied gas with clean energy sources such as propane and biomass gas, so as to reduce carbon emissions. Meanwhile, by applying waste heat recovery technology, the waste heat generated by flames can be utilized for preheating soil or driving auxiliary equipment, which is expected to increase energy utilization efficiency by more than 30%.

6. Conclusions

As a promising soil disinfection technology, soil flame disinfection has been comprehensively summarized and discussed in this paper regarding its latest research progress and application status. From the perspective of development trends, the mechanism research and precision control technology of this technology will present four major characteristics in the future: refined mechanism research, intelligent control technology, diversified application scenarios, and industrial ecological collaboration. This indicates that soil flame disinfection technology is evolving from extensive combustion to a precise, intelligent, and eco-friendly direction, and will play a core role in ensuring food security and promoting the green transformation of agriculture in the future.

However, the current development of this technology still has obvious shortcomings. On the one hand, the depth of mechanism research is insufficient, and the underlying logic of the interaction between high temperature and soil microorganisms, nutrients, pathogenic organisms, etc., has not been fully clarified. On the other hand, practical applications encounter multiple challenges, including: (1) Soil heterogeneity leads to inconsistent disinfection efficacy, as significant variations in the thermophysical properties—such as thermal conductivity—of soils with different textures, moisture con-tents, and organic matter levels make uniform heating difficult to achieve; (2) Prominent safety risks arise from open-flame high-temperature operations, which pose ignition hazards and require stringent protective measures for both operators and field facilities; (3) Limited field scalability constrains the adaptability of existing equipment under complex topographic conditions, while energy utilization efficiency and operational productivity still require substantial improvement. Additionally, the accuracy of existing models for temperature transfer and prediction needs further enhancement.

Addressing these limitations is a prerequisite for the reliable integration of flame disinfection into continuous cropping systems, organic farming, and conservation agriculture frameworks. The true potential of flame disinfection is unlocked when it is strategically incorporated into broader agricultural management regimes. We believe that the approaches that can be combined with sustainable agricultural systems include: (1) Organic Production Systems: Serving as a primary physical method for weed and soilborne disease control, reducing reliance on manual weeding and complying with organic certification standards. (2) Conservation Agriculture: Complementing no-till or reduced-till practices by managing weeds and slugs without reversing the soil profile, thereby preserving soil structure and moisture. (3) Integrated Pest Management (IPM): Acting as an effective tactical option to disrupt pest and pathogen lifecycles, thus reducing the selection pressure associated with continuous biocontrol or chemical use. Furthermore, combining flame disinfection with soil amendments (e.g., biochar or compost) presents a promising strategy; the thermal process can eliminate pathogens while the amendments subsequently support the rapid re-establishment of a beneficial soil microbiome, enhancing system resilience. Based on this, this paper also proposes key research directions to be addressed in the future. These should be explicitly framed within the context of sustainable system integration: deepening the scientific mechanism of high-temperature physical disinfection and upgrading the precision of intelligent control technology to achieve precise management of the disinfection process, while concurrently investigating its long-term impacts on soil health indicators and its synergistic effects with other sustainable practices. This holistic approach is essential for ultimately promoting the technology to leap from “feasible” to “efficient and reliable” within the future of sustainable agriculture.