Pesticide Degradation: Impacts on Soil Fertility and Nutrient Cycling

Abstract

The widespread use of pesticides in modern agriculture has significantly enhanced food production by managing pests and diseases; however, their degradation in soil can lead to unintended consequences for soil fertility and nutrient cycling. This review explores the mechanisms of pesticide degradation, both abiotic and biotic, and the soil factors influencing these processes. It critically examines how degradation products impact soil microbial communities, organic matter decomposition, and key nutrient cycles, including nitrogen, phosphorus, potassium, and micronutrients. This review highlights emerging evidence linking pesticide residues with altered enzymatic activity, disrupted microbial populations, and reduced nutrient bioavailability, potentially compromising soil structure, water retention, and long-term productivity. Additionally, it discusses the broader environmental and agricultural implications, including decreased crop yields, biodiversity loss, and groundwater contamination. Sustainable management strategies such as bioremediation, the use of biochar, eco-friendly pesticides, and integrated pest management (IPM) are evaluated for mitigating these adverse effects. Finally, this review outlines future research directions emphasizing long-term studies, biotechnology innovations, and predictive modeling to support resilient agroecosystems. Understanding the intricate relationship between pesticide degradation and soil health is crucial to ensuring sustainable agriculture and food security.

1. Introduction

Pesticides are chemicals or biological substances used to prevent, control, or eliminate pests that can harm crops, animals, humans, or property. In modern agriculture, pesticides are crucial in reducing pests, improving crop yields, minimizing harvest losses, decreasing the incidence of livestock diseases, and controlling plant disease vectors [1]. Without pesticides, there would be a loss of 54% of vegetables, 78% of fruits, and 32% of cereals [2]. Therefore, pesticides significantly alleviate hunger by providing abundant, high-quality food, increasing agribusiness revenues, enhancing nutrition, and increasing the availability of a wide range of viable crops, thereby improving life expectancy and increasing export revenues [3]. Broadly, pesticides are categorized into four classes based on their chemical classes, functional groups, mechanism of action, and toxicity [4]. Based on their chemical structure, pesticides are classified as organic and inorganic. Inorganic pesticides include sulfur, lime, copper, copper sulfate, and ferrous sulfate. Organic pesticides are more complex and categorized into many types, including organochlorines, organophosphates, carbamates, pyrethroids, triazine herbicides, benzimidazole nematocides, metaldehyde molluscicides, and metal phosphide rodenticides [5]. Moreover, pesticides are also classified based on their target pests, such as insecticides used to control insects, fungicides used to control fungi, and herbicides used to control weeds [6].

Furthermore, the increasing application of pesticides influences soil health and fertility, which plays an essential role in maintaining ecosystem health. The nutrient cycles, energy flow, resilience to stress, and high biodiversity and stability represent a healthy ecosystem [7]. Soil health is closely linked to soil quality, which is defined as the capability of the soil to function within the ecosystem boundaries to sustain organic productivity, maintain environmental quality, and enhance plant and animal health [7]. Soil supports various life processes, including the supply of water and nutrients. It serves as a source and anchorage for plants, food webs, and other regulatory functions, such as gaseous exchange, nutrient cycling, microbial diversity, pollutant detoxification, and carbon sequestration [8]. Thus, maintaining soil fertility is essential for agriculture, ensuring sustainability, high productivity, and economic viability. Fertile soil contains an appropriate quantity of major and minor nutrients necessary for plant growth [9]. Nutrient cycling is a fundamental ecological process that governs the availability, transformation, and movement of essential elements, such as nitrogen (N), phosphorus (P), potassium (K), and sulfur (S), within the soil ecosystem [10]. This cycle involves complex interactions among soil minerals, organic matter, microbial communities, plant roots, and environmental factors. Microorganisms play a central role in decomposing organic matter and converting nutrients into forms that are bioavailable through processes such as mineralization, nitrification, and nitrogen fixation. Efficient nutrient cycling supports plant productivity, maintains soil structure, and enhances microbial diversity, key indicators of soil health [11].

Disruptions to soil cycle, such as those caused by pesticide residues or their degradation by-products, can impair nutrient availability, reduce microbial activity, and ultimately compromise the sustainability of agroecosystems. Therefore, understanding the influence of external inputs, including pesticides, on nutrient dynamics is critical for promoting resilient and fertile soils. In modern agriculture, the application of pesticides is a double-edged sword. On the one hand, pesticides play a crucial role in addressing the issue of food security by increasing agricultural productivity; however, on the other hand, pesticides pose a serious threat to soil health and the environment. For example, after application, pesticides can enter the environment and undergo transfer or degradation. The degradation of pesticides in the environment produces a variety of by-products [12,13,14]. Pesticides move from their target area to other non-target locations or environments by runoff, spray drift, volatilization, leaching, and adsorption [15]. For example, in leaching, various factors such as solubility, permeability, adsorption coefficient (K_oc), and aerobic soil half-life (DT₅₀) of pesticides play an important role. Persistency is another factor that affects leaching; for instance, the persistency of imidacloprid in the soil is (DT₅₀ in soil = 187 days), which represents a higher potential for environmental mobility and long persistence in the soil [5]. The degradation products of chemical residues raise concerns due to their ability to contaminate soil and cause environmental issues, which pose significant threats to the soil. In some cases, these degraded products are more prevalent or toxic than the parental compound, and the toxicity of the transformed compounds can vary; however, some studies reported similar or less toxicity than the parent compound [16]. On the other hand, the frequent application of pesticides can lead to soil contamination and nutrient loss [17]. The primary source of receiving pesticide contaminants is soil, which has higher toxicity than any other ecosystem. The applied pesticides directly settle on the soil and can persist there for weeks to years, altering the soil’s physicochemical conditions [18]. For instance, pesticides such as organochlorine, DDT, endosulfan, endrin, heptachlor, and lindane are persistent in nature, contaminate soil and alter its pH, which can drastically change the soil biota, including nitrogen-fixing bacteria, phosphate-solubilizing microbes, and bacteria that decompose organic matter, resulting in massive degradation of soil nutrients [19].

Therefore, this review aims to critically examine the dual impact of pesticide use, highlighting both its agricultural benefits and the unintended consequences of its degradation on soil health. Specifically, the paper focuses on elucidating the mechanisms by which pesticides degrade in soil environments and how these processes influence soil fertility and nutrient cycling. While numerous studies have addressed the fate of pesticides or their toxicological impacts, this review uniquely integrates these aspects through the lens of soil functionality, emphasizing the direct and indirect effects of degradation products on microbial communities, nutrient dynamics, and soil physicochemical properties. By bridging insights from soil science, environmental chemistry, agronomy, and microbial ecology, this review offers a multidisciplinary synthesis that is currently lacking in the literature. Furthermore, it provides a forward-looking perspective by identifying research gaps, proposing sustainable management strategies, and evaluating the long-term implications of pesticide degradation for soil health, agricultural sustainability, and food security in the context of global environmental change.

2. Pesticide Degradation Mechanisms in Soil

Generally, the degradation of pesticides depends on various factors of the soil and soil processes, such as adsorption, plant uptake, surface and subsurface transport, microbial degradation, and chemical hydrolysis. Pesticides subjected to the movement away from their point of application are either degraded or not degraded, detoxified, or removed with the harvested crops [1]. Pesticide degradation pathways and the fate of pesticides are complex, depending on the nature of the chemicals, their structure, volatility, solubility, formulation, and properties of the soils involved. The breakdown of pesticides can be categorized as transport away, localized losses, and removal of chemicals from the environment [2]. Pesticide degradation in soil occurs through abiotic processes such as hydrolysis, photodegradation, and chemical oxidation, and biotic processes primarily mediated by soil microorganisms that enzymatically break down pesticide compounds into simpler, often less toxic forms [20,21]. Figure 1 explains the detailed mechanism of pesticide degradation in soil.

2.1. Abiotic Degradation

2.1.1. Photodegradation

Photodegradation is the most critical degradation factor among various other processes that determine the fate of pesticides in the field [5]. The process of photodegradation is accomplished through direct photolysis, and indirect photolysis occurs within shallow surface layers of the soil. In direct photolysis, the pesticide directly absorbs light and undergoes photolysis, becoming excited, and transforming depending on the available activation energy. In the case of indirect photodegradation, pesticides react with other species produced photochemically for their degradation and are transformed into different products [22]. In the presence of sunlight, photodegradation occurs in the shallow zone of the soil, depending on its depth, soil characteristics, and the photodegradation mechanism. Moreover, the intensity and spectrum of the sunlight depend on various environmental conditions such as seasons, altitude, latitude, and atmospheric state. The penetration depth of the sunlight varies from 0.2 to 0.7 mm in direct and indirect photolysis processes, up to 2 mm [6]. Furthermore, soil texture, moisture, and wavelength also govern the penetration depth [7]. Higher porosity and sandy soil are also cases of direct photolysis [8]. Moreover, moisture in the soil opens pores, facilitating the deeper penetration of light and consequently, more direct photolysis [9].

The photodegradation of the pesticides occurs due to the absorption of light energy, specifically above 285 nm. The photocatalytic decomposition of pesticides involves isomerization, substitution, or oxidation, which depend on the properties of pesticides, environmental conditions, and other factors [10]. Most photodegradation processes require photocatalysts such as titanium dioxide and zinc oxide. These reactions possess high photoactivity, minimal environmental toxicity, low cost, and resistance to photo-corrosion [11]. To remove and degrade pesticides in soil and aqueous environment, various advanced oxidation processes (AOPs), such as Fenton, photo-Fenton, and heterogeneous photocatalysis mechanisms, have been explored [12]. They are based on the production of numerous free hydroxyl (HO•) and superoxide (O₂⁻•) radicals, which can break the pollutants into lower molecular weight intermediates and inorganic precursors [13]. While AOPs are well-studied in aqueous models, their application in real soil environments is more complex due to soil heterogeneity, limited reagent penetration, radical scavenging by soil organic matter, and variable pH conditions. As a result, AOPs in soil often require optimized delivery methods (e.g., soil washing or slurry-phase treatments) to enhance efficacy compared to aqueous systems [12].

Many studies reported the role of organic photosensitizers in accelerating photochemical reactions, thereby enhancing the degradation rate of numerous chemical compounds. For example, upon exposure to light, pyrethroids can undergo isomerization, followed by transformations such as 3,3-dimethacrylate formation, ester bond cleavage yielding carboxylic acid derivatives, and reductive decarboxylation and dehalogenation (Figure 2). These photochemical reactions contribute significantly to the breakdown of pyrethroids in the environment, ultimately influencing their persistence, toxicity, and impact on soil and water ecosystems [5]. Furthermore, investigating the degradation of Butachlor and Ronstar herbicides under natural sunlight, employing diethylamine as a photosensitizer [23]. The compound containing amines such as diethylamine, triethylamine, and diethylphenylene diamine facilitates photodegradation by generating various reactive species. Similarly, another study reported the significant degradation of Chlorpyrifos and Diuron in the presence of fructose, which acted as a photosensitizer [14]. Furthermore, Fernández-López et al. [24] reported the photodegradation of the Isoxaflutole herbicide using Riboflavin as a sensitizer through processes such as Fenton and photo-Fenton, and their findings indicated photo-Fenton as more efficient in degrading Isoxaflutole. Additionally, the photodegradation of Dichlorvos (DDVP) was reported using stimulated sunlight and dissolved oxygen [15].

Overall, photodegradation plays a crucial role in the dissipation of pesticides on soil surfaces, particularly under strong sunlight and favorable soil conditions. This pathway is especially dominant for photolabile pesticide classes such as pyrethroids, organophosphates, and certain herbicides like Butachlor, Diuron, and Isoxaflutole, which contain light-sensitive functional groups. The efficiency of degradation often depends on the presence of photosensitizers, soil texture, moisture, and sunlight intensity. Therefore, photodegradation is considered a key abiotic mechanism for reducing pesticide persistence in exposed, sunlit agricultural soils.

2.1.2. Hydrolysis

Due to adsorption and catalytic reactions, pesticide reactions occur more frequently in soil than in soil-free environments [16]. Hydrolysis is a traditional degradation method, and pesticides such as organophosphorus, organochlorine, and organonitrogen pesticides contain heteroatoms that can be hydrolyzed in alkali conditions in the presence of metal compounds [16]. Furthermore, harmful compounds would be produced during hydrolysis [17]. The factors that influence chemical hydrolysis are the presence of organic matter and clay content with a large surface area, which enhances the hydrolytic conversion of pesticides. Specifically, the soil pH significantly impacts the hydrolysis of acidic and other base-hydrolyzed compounds. For example, the hydrolysis of chlorpyrifos is enhanced under basic conditions. Moreover, temperature is also a significant factor in the hydrolytic degradation of pesticides [18]. For hydrolysis, moisture plays a significant role alongside pH and temperature in the degradation of pesticides. Moisture also plays a crucial role in the development of soil microorganisms, which are crucial for maintaining soil health [19]. Moisture is a critical factor in determining pesticide solubility as it enhances the bioavailability of pesticides in soil, facilitating microbial degradation [25]. Moreover, studies have reported the role of moisture in pesticide degradation, such as the degradation of chlorpyrifos and fenamiphos, which was observed to be slow at 20% moisture content. However, a significant increase in degradation was observed at 40% and above, as reported by Barka et al. [20].

In summary, hydrolysis is a key abiotic degradation pathway for pesticides that contain hydrolyzable functional groups, particularly organophosphorus, organochlorine, and organonitrogen compounds. This process is strongly influenced by soil pH, moisture, temperature, and the presence of clay and organic matter, which together affect the solubility and catalytic transformation of pesticides. Hydrolysis tends to be more dominant for alkaline-sensitive pesticides like chlorpyrifos and plays an important role in reducing their persistence under favorable environmental conditions.

2.1.3. Chemical Oxidation and Reduction

A substantial proportion of pesticides used in agriculture bioaccumulate, leach, and persist in the soil for extended periods, making it essential to determine their stability and potential toxicity in the soil. These compounds are mineralized into carbon dioxide, water, and other minerals. However, varying intermediate degradation products are produced, with varying toxicity. Moreover, pesticides and their degraded compounds interact with the soil through various mechanisms, including Van der Waals forces, ion exchange, hydrogen bonds, hydrophobic interactions, charge transfer complexes, and covalent bond formation [21]. The strength of bonding depends on the chemical and structural properties of pesticides, and this interaction is highly sensitive to environmental changes. For example, residues that are ionically bonded to soil organic matter can be released due to variations in soil pH. However, various studies suggest that with aging, adsorbed residues become stable and resistant to degradation [22].

Figure 3 illustrates the photochemical degradation of pesticides. Chemical oxidation and reduction play a secondary but important role in degrading herbicides and redox-sensitive pesticides, especially those bound to soil particles. These processes influence the transformation of aged or strongly adsorbed residues, with outcomes affected by soil pH, redox potential, and pesticide structure.

2.2. Biotic Degradation

Biotic degradation refers to the breakdown of pesticide compounds by living organisms, predominantly soil microorganisms such as bacteria, fungi, and actinomycetes. This process plays a crucial role in determining the persistence, mobility, and ecological impact of pesticides in soil ecosystems. Through various metabolic pathways, microorganisms can utilize pesticides as sources of carbon, nitrogen, or energy, transforming them into simpler, often less harmful compounds. The efficiency and pathways of biotic degradation are influenced by factors such as microbial community composition, soil physicochemical properties, and the chemical structure of the pesticide. Additionally, soil enzymes, produced by microbes or plant roots, contribute significantly to the degradation process by catalyzing specific reactions involved in pesticide transformation.

2.2.1. Microbial Metabolism of Pesticides

Microbes metabolize pesticides as nutrients for their growth and degrade them into inorganic compounds, such as carbon dioxide and water [26]. Microbial populations interact with the target compound in both physical and chemical manner and ultimately degrade it either absolutely or render it into less toxic compounds by incorporating some structural changes [27]. Among microorganisms, bacteria, fungi, and actinomycetes are the potential microbes that degrade pesticides into by-products, e.g., the microbial degradation of aldicarb, which is a two-step process. The First step is sulfur oxidation, the aldicarb degrades into aldicarb sulfoxide and aldicarb sulfone. In the second step, aldicarb sulfoxide and aldicarb sulfone are further degraded by the action of aldicarb hydrolase produced by Enterobacter cloacae into carbon dioxide (CO₂), amine, N-methyl-carbamic acid, oximes, and nitriles [22]. The variety of bacterial species is highly efficient in the degradation of pesticides, including some important genera such as Bacillus, Klebsiella, Flavobacterium, Acinetobacter, Aerobacter, Alcaligenes, Micrococcus, Neisseria, Sphingomonas, Burkholderia, Pseudomonas, and Arthrobacter [28]. The degradation ability of the mixed culture is higher than that of the individual strain [29]. For example, a study was conducted on the degradation ability of bacteria of the genus Flavobacteria and Micrococcus, which degraded a lower concentration of aldrin at 0.2 mg, compared to both strains present together at an incubation of 12 days [30]. The co-cultivation of bacterial species enhances degradation by the utilization of metabolites of another bacterium as a nutrient medium for their growth and development [31].

Overall, microbial metabolism is a primary degradation pathway for many organic pesticides, particularly carbamates and organophosphates. Mixed microbial cultures, especially those involving genera like Pseudomonas, Bacillus, and Flavobacterium, often exhibit enhanced degradation efficiency, making microbial consortia crucial for effective bioremediation in contaminated soils.

2.2.2. Role of Soil Enzymes in Pesticide Breakdown

The main processes through which pesticide degradation takes place are oxidation, reduction, hydrolysis, dehydrogenation, dehalogenation, decarboxylation, rearrangement, conjugation, and isomerization [23]. Four major classes of enzymes are responsible for the biodegradation of pesticides, namely hydrolases, translocases, oxidoreductases, and transferases [24]. Hydrolases that are involved in the degradation of organophosphate compounds and carbamates [25] include esterases, which are further classified into phosphodiesterase, phosphotriesterase, and monophosphatases [26]. Moreover, oxidoreductases, which are classified into peroxidases, monooxygenases, dioxygenases, and oxidases, are involved in the various oxidative degradation of pesticides. The peroxidases and oxidases are present in fungi, bacteria, and plants and are involved in the breakdown of multiple xenobiotics by redox reactions [27]. Furthermore, transferases such as acetyltransferases, methyltransferases, and glutathione S-transferases (GSTs) are another broad group of enzymes classified based on the chemical group to which they attach pesticides [26]. The biotransformation of pesticides is very important to reduce their persistence and toxicity, which occur in two main phases, I and II [28]. The phase I reactions are particularly involved in initiating detoxification, which involves various chemical reactions such as oxidation, reduction, and hydrolysis. These chemical reactions introduce functional groups such as hydroxyl, carboxyl, or epoxide into the pesticides, which increase degradation through redox reactions or hydrolysis and make them susceptible to detoxification in phase II reactions. Phase II reactions are involved in the overall detoxification process. In this phase, the modified compounds from Phase 1 undergo further modification and conjugation with endogenous molecules such as glutathione, amino acids, phosphate, sulfate, sugars, etc. These compounds are more water soluble and less toxic compared to the original compounds [28,29].

In summary, soil enzymes, particularly hydrolases, oxidoreductases, and transferases, play a critical role in the biodegradation of organophosphates, carbamates, and other xenobiotics. These enzymatic processes, especially through Phase I and Phase II detoxification reactions, significantly enhance pesticide transformation, reduce persistence, and support microbial-driven soil remediation.

2.3. Factors Affecting Pesticide Degradation

A variety of complex dynamic physical, chemical, and biological processes determine the behavior of pesticides in soil, including sorption-desorption, volatilization, and biological and chemical processes. Figure 4 explains the factors contributing to the degradation of pesticides in soil.

2.3.1. Soil Type and Composition

The chemical and physical properties and extent and strength of sorption reactions in soil play a major role in the retention, mobility, and decomposition of pesticides. The mineral and organic components are involved in the sorption interactions. The mobility of pesticides is associated with the total organic content and the nature of the organic content [32]. The soluble and insoluble fractions of organic matter encompass the total organic matter, although the soluble portion typically represents a small component of the soil. In soil with low organic matter, the mobility of the pesticide is influenced by the active inorganic fraction, such as clay; an increase in clay content leads to a reduction in pesticide mobility. Moreover, the composition of minerals in the clay and the presence of dominant cations in the soil play a significant role in determining pesticide behavior [25]. Substantial evidence has reported that pesticides can also interact with the soluble fractions of soil organic matter, and many factors, such as polarity and molecular structure, influence the nature and degree of interactions [33]. For example, atrazine has been shown to form solution-phase complexes with dissolved organic matter [34]. Similarly, paraquat’s association with dissolved organic matter has also been reported [35]. Furthermore, the hydrophobic interaction of pesticides with dissolved organic matter has also been reported [34]. An increase in the mobility of atrazine was reported due to an increase in the concentration of dissolved organic matter in the presence of soil [35] and a hydrophobic organic chemical such as DDT [36]. The detection of pesticides in the groundwater indicated the transport of such chemical compounds through the soil [37]. This transport may be facilitated by processes such as the formation of soluble complexes with the soil components of the soil solution, such as dissolved organic matter, or by the limited interaction of these pesticides with both organic and inorganic soil materials. The factors such as competitive effects, interaction reversibility, and the principle of mass action influence the distribution of pesticides. For instance, the interaction of atrazine with clay minerals is reversible compared to the organic matter [38].

2.3.2. Moisture Content and Temperature

Moisture content and temperature are two critical environmental factors that significantly influence pesticide degradation in soil and agricultural systems. Moisture facilitates microbial activity and chemical hydrolysis, both of which contribute to the breakdown of pesticide compounds. In adequately moist soils, microbial populations thrive and enzymatic degradation of pesticides is enhanced, whereas overly dry or waterlogged conditions can suppress microbial function and slow down degradation. Temperature also plays a vital role by affecting the rate of microbial metabolism and chemical reactions [39]. Higher temperatures generally accelerate degradation processes by increasing the kinetic energy of molecules and microbial enzymatic activity. However, extremely high temperatures may denature enzymes or volatilize certain pesticides, reducing their persistence and potentially leading to environmental contamination. Together, optimal levels of moisture and moderate to warm temperatures promote efficient pesticide degradation, thereby reducing their environmental persistence and potential toxicity [40].

2.3.3. Organic Matter Content

The incorporation of organic matter into the soil increases the concentration of dissolved organic matter [30]. Moreover, it enhances microbial activity due to an increased availability of organic molecules such as sugars and amino acids [20]. Many studies have been conducted on the influence of organic matter on the degradation of pesticides in soil [21]. For example, Spark et al. [33] observed a reduction in the degradation rate of terbuthylazine by the addition of urban sewage sludge, corn straw, and poultry in agricultural soil. Conversely, few studies reported that organic matter has no effect on pesticide degradation. For instance, it has been reported that the amendment of compost had no effect on the glyphosate degradation [34]. However, this study had earlier found that the increased atrazine degradation occurred in the same soil [40]. The addition of organic matter may reduce the mineralization of pesticides by sorption [35]. But on the other hand, it stimulates microbial growth due to nutrient incorporation [36]. Miller et al. [37] determined the degradation of napropamide in both amended with cattle dung (CD) and palm oil mill effluent (POME) and non-amended soil, followed by first-order kinetics. They absorbed the longest half-life in the soil with 20 mg/ha CD, while the shortest half-life was determined in the non-amended soil. They reported slow degradation in the presence of CD and POME, and this was due to the sorption of organic amendments, which shielded it from microbial degradation [38].

2.3.4. pH and Redox Potential

pH affects the process of chemical speciation, particularly for the ionizable compounds and microbial activity. Numerous studies reported that an increase in pH generally enhances microbial activity, which leads to accelerating the degradation of many pesticides. However, the degradation ability of microbes declines when pH exceeds 8–8.5. Particularly for ionizable compounds, pH affects the sorption behavior by influencing the degree of ionization. The increase in pH weakens the sorption behavior of these compounds, making pesticides more accessible for microbial attack. Conversely, the pesticides undergo abiotic degradation, and an increase in pH can negatively impact pesticide degradation, such as sulfonylureas. Moreover, the effect of pH is compound-specific and depends upon whether the mechanism is biotic or abiotic [39]. Redox conditions and the availability of dissolved organic matter also determine the fate of pesticides. For instance, Omar et al. [40] studied the effect of redox conditions and the effect of added dissolved organic material (DOM) on the biodegradation of four pesticides, including 2,4-dichlorophenoxyacetic acid (2,4-D), 2,6-dichlorobenzamide (BAM), mecoprop-p (MCPP), and bentazone. They observed minimum (≤33.77%) pesticide degradation in anaerobic conditions without DOM. Additionally, the addition of DOM reported improved 2,4-D degradation under nitrate-reducing conditions. The depletion of fulvic acids from DOM was observed, suggesting the importance of DOM components for microbial activity. These findings suggested that the interaction of DOM, redox conditions, and microbial activity could be a useful method for pesticide degradation. Various geochemical conditions influenced the degradation of pesticides, specifically, the availability of electron acceptors (redox potential) and the quality of dissolved organic matter [41].

In addition to pH and redox potential, soil texture plays a key role in pesticide degradation. Fine-textured soils (e.g., clay-rich soils) typically exhibit higher sorption capacity due to larger surface area and organic matter content, which can limit pesticide bioavailability and slow microbial degradation [7]. Conversely, sandy soils with low organic matter allow greater pesticide mobility and faster leaching, often enhancing abiotic degradation but reducing microbial activity [8]. Thus, degradation dynamics differ across soil textures based on their influence on sorption, moisture retention, aeration, and microbial habitats.

3. Influence of Pesticide Degradation on Soil Fertility

3.1. Effects of Various Pesticides on Soil Microbial Communities

Soil microflora includes a variety of bacteria, fungi, protozoa, algae, and viruses involved in various essential functions in agroecosystems. These microorganisms are involved in numerous fundamental functions in soil, such as nutrient cycling, soil fertility, promoting plant growth, and the decomposition of both organic and inorganic matter. Furthermore, soil microbiota impacts soil physical properties such as structure, porosity, aeration, and water infiltration by stabilizing soil aggregates [42]. Pesticides, applications used to protect crops, can directly or indirectly impact the soil microbial activity. However, the knowledge of predicting the impact of a pesticide on various soil microbial communities is still limited. Certain pesticides may promote the growth of microorganisms, while others inhibit or have no noticeable effect when applied at the recommended dose. Furthermore, traditional microbial analysis methods, such as standard plate count methods, often lack precision because, in laboratory conditions, only about 1% of the soil bacteria can be cultured. Moreover, the molecular techniques to determine soil microbial communities offer a promising alternative [43]. For example, the effect of pesticides on soil microbial communities could be assessed by determining carbon utilization ability and nitrification. The reliability of the nitrification test is likely because soil fungi do not participate in nitrification, and only a small number of bacterial species can carry out this process. Recently, studies have reported using functional genes such as amoA and amoB, which are involved in the process of nitrification, to determine the influence of pesticides on bacteria [44]. Moreover, some mRNA quantification studies showed that the process of nitrification is highly susceptible to certain pesticides. Other molecular sequencing studies have also reported a change in the microbial community structure due to the influence of pesticides [45].

Table 1. Impact of pesticides on soil microbial diversity and functions.

Chemical Groups	Pesticides	Observed Effects	Reference
Fungicides and bactericidal	Captan	Declined fungal growth, specifically reduced fungal hyphae, density, and lowered carbon and nitrogen content.	[30]
	Captan and chlorothalonil	Inhibited microbial respiration	[31]
	Chlorothalonil and azoxystrobin	Fungal toxin	[48]
	Metalaxyl and mefenoxam	Toxic to nitrogen-fixing bacteria	[24]
	Mancozeb and dimethomorph	Suppressed bacterial and fungal growth	[50]
	Diazinon and linuron	Decreased microbial colony-forming units	[50]
Insecticides	DDT	It affected bacteria and fungi, but showed a limited effect on fungi	[51]
	DDT and arsenic	Significant reduction in the carbon biomass, including bacterial and fungal biomass	[52]
	Chlorpyrifos and dimethoate	Had adverse effects on the collembolan density	[53]
	Cypermethrin and thiomethoxam	Detrimental to the soil microorganisms	[54]
	Carbofuran and methamidophos	Increased microbial growth	[23]
	Fenamiphos	Detrimental to microbial growth	[55]
Herbicides	Glyphosate	Considerable reduction in bacterial and fungal population. Increased in actinomycetes activity and microbial activity by 9–19%	[32]
	Atrazine and Metolachlor	Reduction in microbial growth and changed the composition and diversity	[25]
	Butachlor	Suppressive effect on microbial growth	[33]
	Diuron and chlorotoluron	Influenced microbial development	[33]
	Pendimethalin	A decline in the population of rhizobia and nematodes in the soil was observed	[35]
Heavy metals	Copper	Negatively influencing soil microbial biomass and impairing soil microbiota	[35]
	Arsenic	Suppressed microbial biomass, enzymatic activity, and respiration of soil	[34]

summarizes how pesticides affect soil microbial structure, enzymatic activities, and community structure. For instance, fungicides such as Captan and Chlorothalonil have been reported to suppress fungal growth and respiration [46,47]. Metalaxyl and Mefenoxam were also shown to have a toxic effect on nitrogen-fixing bacteria [48]. Furthermore, Mancozeb, dimethomorph, Diazinon, and linuron showed a suppressive effect on soil microbial growth activity [49]. Noticeably, insecticides such as DDT, arsenic, Chlorpyrifos, dimethoate, cypermethrin, thiomethoxam, carbofuran, methamidophos, and fenamiphos have been shown to reduce microbial activity and reduce the activity of beneficial microbes such as collembolans and disrupt essential metabolic processes [39,40,50,51,52]. Herbicides, including Glyphosate, atrazine, metolachlor, butachlor, diuron, chlorotoluron, and pendimethalin lead to a reduction in microbial activity, a change in microbial community, and selective stimulation of actinomycetes [50,51,52,53]. Heavy metals such as copper and arsenic are particularly toxic to the microbial community, causing a reduction in microbial biomass, enzymatic activity, and soil respiration [54,55].

Emergence of Pesticide-Resistant Microbial Strains

The emergence of antibiotic resistance is one of the critical concerns associated with pesticide applications in agricultural soil. Several pesticides, particularly those with antimicrobial properties, can create selective pressure, leading to the evolution and dissemination of the resistance gene in soil microbial consortia. Studies have shown that certain pesticides can develop resistance mechanisms in microbes similar to those used against antibiotics. For example, insecticides such as chlorpyrifos and herbicides like glyphosate have been associated with increased antibiotic tolerance in soil-dwelling microorganisms. This occurs because antibiotics and pesticides have similar cellular attacking mechanisms, enabling bacteria to evolve resistance to the other inadvertently [56].

Table 2. Effect of pesticides on the microbial enzymes’ activity.

Pesticides	Enzymes	Observed Effects	Reference
Captam and thiram	Nitrogenase in Azospirillum brasilense	Suppressed enzymatic functions	[69]
Fenvalerate and cuprosan	Nitrogenase	Observed inhibition	[36]
Profenophos	Nitrate reductase	Enzyme activity reduced	[37]
Terbutryn, Simazine, and Prometryn	Nitrogenase	Affected nitrogen fixation activity	[38]
Glyphosate	Dehydrogenases	Temporarily inhibited	[70]
Brominal and Selecron	Cellulase	Affected the activity	[71]
Carbendazim, imazetapyr, and thiram	Nitrogenase	Activity reduced	[72]
Oxafun, Funaben, and Baytan	Nitrogenase	Higher concentration decreased the activity	[73]
Metalaxyl	Urease and phosphatase	Inhibited urease phosphatase activities; increased initially and then decreased	[74]
Methabenzthiazurn and Terbutryn	Nitrogenase	Inhibited nodulation and impaired enzymatic activity	[75]
Atrazine and Northrin	Dehydrogenases	Stimulated at low doses and inhibited at higher concentrations	[76]
Azoxystrobin, Tebuconazol, and Chlorothalonil	Dehydrogenases	Less activity in the soil with low organic matter was reported, and no effect on the organic matter in the soil was observed	[77]
Validamycin	Phosphatase and urease	Temporary inhibition and activity recovered	[72]
Fenamiphos	Dehydrogenase and urease	No significant toxicity was observed	[78]
Endosulfan	Dehydrogenases	Increased activity	[41]
Diuron	Urease	No effect detected	[79]
Propiconazole	Cellulase	Activity declined by 5–40%	[80]
Thiamethoxam	Urease, phosphatase, and dehydrogenases	Dehydrogenases and phosphatases were inhibited	[81]
Azoxystrobin	Dehydrogenase, urease, acid and alkaline phosphatases, and catalase	Dehydrogenases showed resistance, with no effect on alkaline phosphatases, and others were inhibited	[82]
Dimethomorph	Dehydrogenase, urease, invertase, and alkaline phosphatases.	Dehydrogenase activity declined, and invertase activity was enhanced without affecting others	[83]

summarizes the key findings from numerous studies that explored the effect of various pesticides and fungicides on soil microbial enzyme activities. Nitrogenases play a crucial role in biological nitrogen fixation by microorganisms such as Azospirillum brasilense. Compounds such as captam, thiram, Fenvalerate, cuprosan, and Terbutryn, exhibited inhibition or reduced nitrogenase activity; additionally, some are reported in the suppression of nodulation [57,58,59]. Notably, dose-dependent effects were also reported, such as Oxafun and Baytan, which showed inhibition at higher concentrations [60]. Dehydrogenase activity was inhibited by Dimethomorph and Thiamethoxam, commonly used to determine microbial respiration [61]. However, some pesticides like glyphosate and endosulfan expressed stimulatory or transient effects based on soil organic content or the concentration of pesticides [62]. Additionally, urease activity is essential for the mineralization of nitrogen. It expressed variable results, such as inhibited, increased, or unaffected outcomes, based on specific compounds or environmental conditions [63,64]. Moreover, phosphatases, which take part in the phosphorus cycle, were inhibited by thiamethoxam and azoxystrobin. Interestingly, metalaxyl and validamycin showed variations in the results, such as increased initially and then decreased [65,66,67,68]. Other enzymes, involved in the carbon cycle, such as cellulase, exhibited reduced activity by compounds like Propiconazole, while the Dimethomorph reported enhanced invertase activity [63].

3.2. Impact on Soil Organic Matter Decomposition

Soil organic matter is critical in influencing the behavior of pesticides in the soil environment [65]. Organic matter is divided into two groups: humic and non-humic substances. Humic substances are more stable than non-humic substances and more resistant to microbial degradation because they contain more stable free radicals. This may facilitate the polymerization, depolymerization, and pesticide interaction among various organic molecules, including environmental pollutants and pesticides. In contrast, non-humic substances include organic compounds with a defined chemical structure, including carbohydrates, proteins, amino acids, lipids, waxes, and low molecular weight organic acids, which have shorter shelf lives and are more easily biodegradable [66]. Soil organic matter exists in liquid and solid forms, and each can interact with pesticides. Dissolved organic matter (DOM) can influence the mobility of pesticides by enhancing or reducing the sorption, which depends on soil characteristics [67]. For example, soils with higher dissolved organic matter showed greater affinity for atrazine, and the lower organic contents showed decreased affinity for atrazine, and vice versa [68]. Similarly, a reduction in the sorption for 2,4-D, naphthalene, and chlorpyrifos was reported with increased dissolved organic matter [63]. In another study, no significant difference was found between DOM, poultry compost, sewage sludge, and the herbicide terbuthylazine, while emended soils displayed increased sorption capability [64]. Another piece of evidence reported that the amendment of organic matters, such as sewage sludge, can increase the sorption of many pesticides, including alachlor, imazethapyr, and rimsulfuron, by various binding mechanisms, which include hydrogen bonding, ionic interactions, and charge-transfer complexes [75].

Table 3. Influence of pesticides on soil biochemical properties.

Pesticides Groups	Pesticides	Biochemical Process	Observed Effects	Reference
Insecticides	BHC and fenvelerate	Carbon mineralization	Increase mineralization by stimulating microbial activity	[93]
	Cyfluthrin and imidacloprid	Nitrification, sulfur oxidation, and denitrification.	Stimulated sulfur oxidation, inhibited nitrification, and denitrification.
	Chlorpyrifos and Quinalphos	Ammonification	Suppressed ammonification	[94]
	Acetamiprid	Microbial respiration	Suppressed microbial respiration activity	[95]
	Imidacloprid (with glyphosate and hexaconazole)	Nitrogen fixation	Toxic to Bradyrhizobium sp.	[96]
	Fenamiphos	Nitrification	Inhibited nitrifying bacteria	[97]
Fungicides	Captan, benomyl, chlorothalonil, and anilazine	Nitrogen mineralization	Mineralization of organic nitrogen was elevated	[48]
	Mancozeb, prosulfuron, and chlorothalonil	Nitrification	Suppressed nitrification	[52]
	Metalaxyl and mefenoxam	Ammonification and nitrification	Improved nitrification efficiency by enhanced conversion of organic nitrogen	[24]
Herbicides	Terbutryn, simazine, premteryn, and benzoate	Nitrogen fixation	Suppressed symbiotic nitrogen fixation via decreased nodulation and nitrogen assimilation	[52]
	Butachlor	Nitrogen fixation	Temporary enhanced N-fixation followed by a decline in nodulation activity	[98]
	Glyphosate, imidacloprid and hexaconazole	Nitrogen fixation	Demonstrated toxic effect on beneficial nitrogen-fixing bacteria	[89]
	Bensulfuron-methyl	Nitrogen mineralization	Resulted in diminished nitrogen release from the nitrogen source	[99]
	Imazetapyr with carbendazim and thiram	Nitrogen fixation	Suppressed formation of root nodules, impairing biological nitrogen assimilation	[100]
Nematicides	Fenamiphos	Nitrification	Inhibited activity of ammonia oxidizing, impairing the nitrogen pathway	[78]
Organochlorines	DDT	Nitrogen fixation	Reduced nodulation in legume, limiting atmospheric nitrogen incorporation	[101]

summarizes the effect of various pesticides on the soil’s microbial processes involved in carbon and nitrogen cycles in the soil. For instance, the pesticides BHC and fenvelerate were shown to increase carbon mineralization [84]. Moreover, other pesticides, including Cyfluthrin and Imidacloprid, were found to suppress nitrification and denitrification while stimulating sulfur oxidation, whereas acetamiprid exhibited a reduction in microbial respiration [85]. Additionally, Imidacloprid with glyphosate and hexaconazole showed a toxic effect against Bradyrhizobium sp., impairing nitrogen fixation [86]. Fungicides are mainly designed to suppress the growth of fungi, but they often affect nitrifying, denitrifying bacteria, and nitrogen mineralization microbes. Captan, benomyl, chlorothalonil, and anilazine have shown enhanced nitrogen mineralization, possibly by altering fungal-bacterial interaction [87]. However, Mancozeb, Prosulfuron, and Chlorothalonil were expressed to inhibit nitrification [88]. Conversely, Metalaxyl, and Mefenoxam reported enhanced nitrification [48]. Furthermore, herbicides mainly impact plant growth but also affect nitrogen fixers and free-living nitrogen-transforming bacteria. Terbutryn, simazine, premteryn, and benzoate suppress nodulation and nitrogen content in legumes [89] while Bensulfuron-methyl decreased nitrogen mineralization by inhibiting nitrogen release from the source [90]. Furthermore, Butachlor exhibited both initially increased nitrogen fixation and then decreased due to toxic buildup [91]. Moreover, Glyphosate with Imidacloprid and hexaconazole showed a toxic effect on nitrogen-fixing strains such as Bradyrhizobium sp. Strain MRM6 [92]. Nematicides, target soil nematodes but can also exhibit side effects on nitrifying microorganisms. Fenamiphos, possibly inhibits the nitrification process by inhibiting the ammonia-oxidizing bacteria [75]. Organochlorines, particularly DDT, 2,4-D, and 2,4,5-T, which are known for their bioaccumulation and persistence in the environment, have a detrimental effect on nitrogen processes, such as reducing nodulation in legumes.

3.2.1. Alterations in Carbon Cycling and Humus Formation

There is a gap in comprehensive studies examining the impact of multiple pesticides on the carbon cycle and associated microbial communities. Therefore, it is crucial to evaluate the impact of pesticides on the carbon cycle and the potential effect of pesticides on microbial enzymatic activities and microbial communities indirectly linked to the carbon cycle. Most existing studies are limited to a small number of functional endpoints or to one or two soil types, and often fail to explore the relationship between functional activity and microbial diversity. Additionally, present studies have only assessed a single or a few pesticides [102]. For example, Tejada et al. [103] explored the impact of three pesticides on microbial physiology and the carbon cycle in two agricultural soils. However, their studies were limited to cellulase enzymatic activities and cellulolytic microorganisms. On the other hand, one critical impact of pesticide degradation is the alteration in humus formation. Certain pesticide residues may disrupt microbial communities responsible for breaking down organic matter, thereby slowing or modifying the humification process. This can lead to a reduced formation of stable humus compounds, essential for maintaining soil structure, nutrient retention, and long-term fertility. In some cases, pesticide by-products may bind with organic matter, forming less bioavailable complexes that hinder nutrient cycling and soil health [84]. Figure 5 explains the process of emergence of microbial resistant strains and reduced soil productivity.

3.2.2. Potential Role of Pesticide Degradation Products in Soil Carbon Sequestration

Recent work suggests that pesticide transformation products can become integrated into stable soil carbon pools through several complementary mechanisms. In many soils, a large fraction of applied pesticide C is found in non-extractable (“bound”) residues that are chemically associated with soil organic matter. For example, tracer studies show that pesticide metabolites can form covalent bonds with humic fractions during humification, effectively “locking” pesticide carbon into refractory soil organic matter [81]. Conceptual models thus distinguish covalently bound residues (NER Type II) from “biogenic NER” (Type III) arising via microbial assimilation [104]. Laboratory experiments confirm this: for instance, fungi incubated with ¹⁴C-labeled pesticides incorporated on the order of 10–15% of the applied C into biomass, whereas bacterial uptake was much lower [46]. Such microbial biomass (and its cellular components) ultimately turns over into soil organic matter, analogous to natural humification. Likewise, pesticide derivatives can sorb or co-precipitate with clays and metal oxides in organo-mineral complexes, further stabilizing C. These pathways mirror natural Soil organic matter (SOM) formation, implying that pesticide–SOM reactions and bioNER contribute to carbon sequestration. At the same time, field studies emphasize that pesticides also perturb microbial carbon processing. In one recent study, multiple pesticide treatments were found to “disrupt the formation of soil organic matter and structure stabilization [47]. In sum, current evidence indicates that pesticide metabolites can enter long-lived SOM pools (via humification, mineral binding, and microbial biomass incorporation) [56] though the net impact on overall carbon sequestration likely depends on soil chemistry and microbial community responses. Furthermore, studies reported that persistent organic pollutants such as organochlorines showed limited water solubility, lower volatility, and higher affinity for soil organic matter (SOM) [87]. These hydrophobic compounds are retained in the soil for a longer time due to hydrophobic interaction, diffusion-driven partitioning, and covalent bonding [49]. In addition, these organic compounds affect soil organic matter, which plays a key role in carbon sequestration due to its strong affinity for glassy carbon domains and its affinity for diffusing into its nano-scale microporous structure [50]. Extensive research on the sequestration of hydrocarbons relied on macroscopic analysis to understand how these compounds interact with soil organic matter. Such studies aimed to identify the influencing sequestration dynamics, such as aqueous solubility, polarity, hydrophobicity, and molecular structure of the contaminant, and soil organic matter with characteristics [51]. Another study by Chung and Alexander [52] demonstrated that the sequestration dynamics of phenanthrene and atrazine in 16 different sterilized soil samples differed in physical and chemical properties. Both compounds, sequestered in all soils, exhibited different rates and extents of sequestration that varied significantly among the soils. Moreover, studies on various soil types, such as laterite, typic fluvaquent, alluvial, and rice rhizosphere soil of rice, reported that different insecticides, such as BHC, phorate, carbofuran, and fenvalerate, belonging to organochlorine, organophosphate, carbamate, and pyrethroid showed higher rate of mineralization rate of organic carbon as compared to control [105,106].

3.3. Effects on Soil Physicochemical Properties

3.3.1. Changes in Soil Structure and Porosity

Soil contains minerals and organic matter grains that join together to form particles, which further aggregate into higher-order structures. Porosity exists throughout the soil profile between particles, grains within particles, and even within individual grains of soil, clay, mineral, and organic matter [40]. The soil surface area within its microspores and smaller mesosphere suggests that the pore structure plays a significant role in sorption. An organic compound is reduced due to capillary force, vapor pressure, and liquid solubility [100]. Pore structure can also significantly influence sorption and desorption [107]. Due to variations in composition and physicochemical properties, soils differ considerably in its capacity and the mechanisms for pesticide adsorption. Soil organic matter (SOM), including living and decomposed organic material, plays a key role in desorption. The significant component of SOM is humic substances, including fulvic acids, humic acid, and humin, which vary in molecular weight and chemical properties and are involved in integral soil function and structure formation, such as porosity, water retention, ion exchange capacity, and chelation of mineral elements. The leading functional group involved in these interactions in humic substances includes hydroxyl (-OH), carboxyl (-COO⁻), and carbonyl (-C=O) groups [108]. Limited studies have been conducted on the soil structure and porosity to determine the effect of pesticides on soil structure and porosity. The models, like the Root Zone Water Quality Model (RZWQM), are currently used by scientists to determine the movement of pesticides through soil with large cracks or pore sizes. This tool is very useful in determining the attachment of pesticides to soil particles or pesticide degradation patterns over time due to various factors such as temperature, moisture, and depth of the soil. RZWQM has a built-in database for many commonly used pesticides’ active ingredients and supports many agricultural management processes, including crop rotations, tillage, irrigation, and pesticide applications [53].

3.3.2. Influence on Water Retention and Infiltration Rates

Pesticide degradation can alter soil physicochemical properties, notably affecting water retention and infiltration rates. Residual compounds from degraded pesticides may modify soil texture and structure by influencing the aggregation of soil particles. This can reduce porosity and clog soil pores, leading to decreased water infiltration [54]. Additionally, changes in microbial activity and organic matter content caused by pesticide breakdown can impair the soil’s ability to retain moisture. As a result, soils may become less capable of supporting healthy plant growth, ultimately diminishing soil fertility and agricultural productivity.

3.3.3. Pesticide-Induced Alterations in Cation Exchange Capacity (CEC)

Pesticide degradation can significantly alter the soil’s CEC, a key indicator of soil fertility. The breakdown products of certain pesticides may interact with clay minerals and organic matter, potentially reducing the number of available exchange sites for essential nutrients such as calcium, magnesium, potassium, and ammonium [55]. Additionally, shifts in microbial activity due to pesticide residues can influence the stability and composition of soil organic matter, further impacting CEC. A reduced CEC limits the soil’s ability to retain and supply nutrients to plants, thereby compromising overall soil health and crop productivity.

4. Influence of Pesticide Degradation on Nutrient Cycling

A healthy ecosystem is characterized by the cohesion of energy flow, nutrient cycling, stability, and resilience to stress [57]. Nutrient cycling is a key indicator of soil health, and nitrogen cycling is among the most studied due to its supporting role in plant growth. The negative impact of pesticides on nontarget biosystems leads to adverse effects on soil biochemical properties, including enzymatic activities. It disrupts the food web, such as beneficial microbes, protists, nematodes, and arthropods [58].

4.1. Nitrogen Cycle

4.1.1. Effects on Nitrogen Mineralization and Nitrification Processes

Studies have reported that pesticides can disrupt the process of organic matter decomposition and mineralization in agriculture and grassland [109], forests [110], and a desert ecosystem [111]. Sukul [62] found a reduction in total carbon and nitrogen contents after metalaxyl exposure to the soil during 30 days of incubation. In soil, a significant amount of organic nitrogen is converted into mineral nitrogen in the presence of soil microbiota via a process known as mineralization. Studies have also reported that the biodegradation of pesticides also promotes the growth and activity of numerous microbes, which in turn stimulate the mineralization of organic matter [81,82]. Furthermore, the application of pesticides increases the process of mineralization, which leads to an enhancement of ammonium NH₄⁺ and nitrate NO₃⁻ levels in the soil [112].

Microbial taxa exhibit diverse resilience or susceptibility to various pesticides. For example, Azospirillum and other anaerobic nitrogen fixers showed enhanced growth after carbofuran application. Moreover, herbicides such as glyphosate and insecticides such as methamidophos are also reported to promote soil microbial growth [113]. Azotobacter, an important nitrogen-fixing bacterium isolated from various rhizospheres, is reported to be tolerant to multiple pesticides. Moreover, some other bacterial strains in the soil have been reported to be pesticide-tolerant, such as Azotobacter, Arthrobacter, Burkholderia, Pseudomonas, and Rhodococcus [114]. Additionally, different Bacillus species have been reported to be tolerant towards various groups of pesticides.

4.1.2. Impact of Pesticides on Nitrogen-Fixing Bacteria and Denitrifiers

In soil, nitrogen-fixing and denitrifying bacteria are essential for converting atmospheric nitrogen into nitrites and nitrates that plants and microbes can utilize, ultimately completing the cycle [115,116]. Most studies have explored the effect of pesticides on nitrogen fixation and nitrification, while relatively few studies have investigated denitrification. For example, a survey of two pesticides involved in denitrification, S-metolachlor and propiconazole, and their potential metabolites, ESA-metolachlor and 1,2,4-triazole, on bacterial denitrification was conducted. This study reported that S-metolachlor had no or little effect on the process of denitrification. Conversely, ESA-metolachlor significantly inhibited denitrification by 65% at a concentration of 10 μg/L. Moreover, propiconazole and 1,2,4-triazole also exhibited reduced denitrification 29–38%, but less pronounced than ESA-metolachlor [117]. The narrow group of microbes phylogenetically can perform nitrogen fixation, such as symbionts (Rhizobium) and free-living (Azotobacter and Clostridium) [118]. Therefore, any detrimental impact on these microbial consortia can significantly impair the nitrogen cycle in the soil. Studies have reported both suppressive and enhancing effects on the microbiota involved in nitrogen fixation and ammonia oxidation in the soil [119,120]. For instance, applying pendimethalin at the recommended dosage resulted in a 62% rise in the growth of N-fixing bacteria and a 36% increase in nitrate production [119]. Conversely, the herbicide clomazone and the insecticide methamidophos reduced the abundance of nitrogenase (nifH) in soil, indicating a decline in the bacterial nitrogen fixation [121]. Moreover, the inhibitory effect of the pesticides has also been reported on the abundance of ammonia-oxidizing microorganisms [122].

4.2. Phosphorus Cycle

4.2.1. Alterations in Phosphatase Enzyme Activity and Phosphorus Availability

Phosphates are a group of enzymes involved in the hydrolysis of esters and anhydrides of phosphoric acid [123]. These enzymes play a central role in the phosphorus cycle [124]. The phosphatases included five major enzyme groups: phosphomonoesterases, phosphodiesterases, phosphotriesterases, pyrophosphatases, and phosphoamidases. In soil, phosphomonoesterases are the most prevalent, likely due to low substrate specificity [125]. Apart from plant growth, phosphatases play a central role in the soil ecosystem [124]. Many researchers reported unchanged or decreased phosphatase activity after various pesticide applications [126]. Studies have reported a decrease in alkaline phosphatase after exposure to fungicides [127] while enhancing acid phosphatase activity. A similar trend is also evident in another study by Zhang et al. [128] after mefenoxam and metalaxyl fungicides in soil at pH 7.2 [96]. Moreover, in the case of herbicides, acid and alkaline phosphatase showed a similar response, either stimulated or unaffected, as observed in the case of imazetapyr [129]. Additionally, herbicides are often reported due to their phosphate inhibition activities [103]. Conversely, the effect was variable in the case of insecticides, with acid and alkaline phosphatases, which may inhibit one type of phosphatase while stimulating another [130]. Overall, insecticides have been reported to have an inhibitory effect on the phosphatase activity [131] involved in the phosphorus cycle.

4.2.2. Role of Pesticide Residues in Phosphate Immobilization or Solubilization

When applied, pesticides can adversely affect the native microbial diversity and disrupt essential soil biochemical reactions, such as the decomposition of organic matter, nitrogen fixation, ammonification, and phosphate solubilization [100]. Many studies have explored the effect of pesticides on bacterial growth and their phosphate solubilization capabilities [132]. For example, a significant reduction in phosphate solubilization was assessed when Klebsiella sp. was exposed to single, double, and triple dosages of the recommended pesticides such as pyriproxyfen, fipronil, imidacloprid, and thiamethoxam, and over 90% reduction was observed with a triple recommended dose of pyriproxyfen [133]. Moreover, similar inhibitory results were noticed in the phosphate solubilization of Pseudomonas putida when exposed to triple doses of fungicides such as tebuconazole, hexaconazole, metalaxyl, and ketazin [134]. In contrast, when exposed to chlorpyrifos, another study observed enhanced phosphate-solubilizing activity in Bacillus sphaericus and Burkholderia cepacia [132]. Furthermore, it was reported that a significant increase in the population of phosphate-solubilizing bacteria occurred when bacteria were exposed to insecticides such as BHC and phorate in the soil, suggesting that these bacteria could utilize these pesticides as a source of nutrients [135]. The process of phosphorus solubilization is facilitated by acidification of the surrounding medium, which decreases the pH and promotes the release of phosphate ions through the chelation of metal cations bound to phosphate ions. The acidification process is predominantly driven by the organic acids released by microbes and the extrusion of protons during ammonium ion assimilation. Organic acid and metal chelation facilitate solubilization and enhance phosphorus availability [136]. Soil microbes release a variety of organic acids as a by-product of metabolism, including gluconic, 2-ketogluconic, 5-ketogluconic, tartaric, acetic, formic, oxalic, malic, alpha-ketoglutaric, succinic, citric, propionic, and lactic acids [136]. Typically, Gram-negative bacteria solubilize mineral phosphates more efficiently than Gram-positive bacteria. This is due to the extracellular aldose oxidation pathway, which enables the breakdown of hexose and releases high-energy organic acids [137]. These organic acids contain unique properties due to their hydroxyl and carboxyl groups, which can form complexes with metal ions and promote phosphate solubilization [138].

4.3. Potassium and Micronutrient Cycling

The degradation of pesticides in soil can significantly influence the mobility and availability of potassium and essential micronutrients such as zinc (Zn), iron (Fe), and manganese (Mn). Pesticide residues and their by-products may interfere with potassium mobility by altering soil structure, ionic balance, or microbial-mediated nutrient release processes [139]. In addition, the bioavailability of micronutrients can be affected through direct chemical interactions; for instance, some degradation products may form insoluble complexes or precipitates with metal ions, reducing their uptake by plants. Chelation reactions involving pesticide metabolites can also sequester micronutrients, making them less accessible in the rhizosphere [140]. These changes can impair nutrient cycling, hinder plant nutrition, and ultimately reduce soil fertility and crop productivity.

5. Environmental and Agricultural Implications

5.1. Reduced Soil Productivity and Crop Yield

Overusing pesticides leads to soil degradation and seriously threatens soil health, leading to food security [105]. It has been reported that around one-third of agricultural production involves using pesticides to control a broad spectrum of pests that damage crops [141]. The highest pesticide application is reported in Asian and certain South American countries, ranging from 6.5 to 60 kg/ha. Countries such as China, the United States, and Brazil are among the highest consumers of pesticides worldwide. For example, in 2020, China used approximately 1.8 million tons, while Brazil and the U.S. used 720,000 and 407,000 tons, respectively. Herbicides constitute the largest share of global pesticide use (around 50%), followed by fungicides and insecticides [141,142]. However, only 0.1% of the applied pesticides reach the target organisms, while the bulk quantity contaminates the atmosphere [142]. The intensified chemical input in the soil reduces organic matter [143]. The overuse of pesticides disrupts the plant physiology, affecting the crop yield and impairing the soil biological processes. Furthermore, the excessive application of pesticides also causes phytotoxicity due to electrolytic leakages from the cellular membrane because of excessive reactive species generation, which leads to the inhibition of chlorophyll, vegetative growth, and overall crop growth. Conversely, the optimal application of pesticides, e.g., 0.21 kg a.i ha⁻¹ for insecticides, 1.44 kg a.i. ha⁻¹ for herbicides and 0.4 kg a.i ha⁻¹ fungicides showed significant results for plant physiology and overall crop yield [144].

5.2. Long-Term Soil Degradation and Loss of Soil Biodiversity

The excessive use of various pesticides to enhance crop yield can also cause soil contamination. Additionally, they can also harm non-target species, including beneficial species [62]. It is impossible to eliminate the pesticides or other pollutants once they enter the environment. The available strategies are limited to either reducing their toxicity or altering mobility to prevent further spread to the ecosystem [145]. The pesticides, after being sprayed on crops, can accumulate on the surface of the leaf or mix with the soil after abscission and alter soil functions [146]. After applying pesticides, they can persist in the soil for weeks to years with higher toxicity than in other ecosystems, thus changing the soil’s physicochemical conditions [60]. Ultimately, pesticides minimize soil fertility, destroy beneficial microbial diversity, and disrupt the biogeochemical cycle with soil chemistry [65].

5.3. Groundwater Contamination and Its Feedback on Soil Nutrients

Currently, a large amount of synthetic organic pesticides is used in agriculture. These pesticides may enter the soil by missing their intended targets through the crop’s surface or subsurface runoff from the application site. The dissipation of pesticides in soil is influenced by various factors such as the nature of pesticides, the cropping system, irrigation practices, and the surrounding climate conditions [66]. Moreover, the rate and extent of pesticide use are influenced by multiple factors, including pesticide properties, soil characteristics, including structure, organic matter, clay composition, and presence of iron oxides, and soil hydrological processes play a significant role. Particularly, hydrophobic pesticides, which have high mobility for leaching into the groundwater due to weak sorption to the soil matrix [67], are quantified by the K_oc values, representing the ratio of pesticides absorbed. Furthermore, pesticides with a k_oc value above 1000 have been observed in ground and drainage water [68]. Additionally, the subsequent leaching of pesticides into the groundwater may also impact the quality of agricultural crops and their products, which in turn poses a health risk to consumers and affects the region [63]. The surface water and groundwater sources are consistently at risk of contamination due to numerous factors such as the flow of pesticides in soil and water, the distance of the application site, the quantity of pesticide used, weather conditions, and climate [64].

5.4. Risks to Sustainable Agriculture and Food Security

Achieving sustainable agricultural productivity and ensuring food safety worldwide are the biggest challenges of the new millennium. Addressing these demands requires modern technologies that can enhance global food production while decreasing environmental damage and preserving the resilience of agroecosystems against a rapidly changing climate [147]. However, for sustainable agriculture, various approaches, such as genetically modified organisms (GMOs) with pest resistance, have been developed to reduce the agrochemical applications. Moreover, other approaches, such as biological and chemical-free farming practices, are gaining attention. The application of marine biomass as a biopesticide also presents a significant opportunity for the development of a sustainable biopesticide. For instance, seaweeds and microalgae are a diverse group of marine photosynthetic organisms. They contain a variety of bioactive compounds such as erpenoids, polyphenols, and sulphated polysaccharides, which offer potential pesticide properties, making them an effective, eco-friendly alternative to conventional chemical pesticides [148]. However, these approaches do not have the capability to fulfill global food demands. Despite growing awareness of the risks of agrochemicals, they remain in use worldwide, especially in tropical and developing countries. Furthermore, many environmentally persistent compounds like dichlorodiphenyltrichloroethane (DDT), hexachlorocyclohexane (HCH), and lindane are banned in many developing nations but are still in use in several developing countries [149].

5.5. Emerging Concerns: PFAS (Per- and Polyfluoroalkyl Substances)-Containing Pesticides and Their Soil Implications

PFAS-containing pesticides have recently emerged as a serious environmental concern due to their extreme persistence, bioaccumulation potential, and toxicity. PFAS compounds are known as “forever chemicals” because they do not readily degrade in the environment, making their accumulation in soil particularly problematic [150]. Some pesticide formulations, especially older ones or those produced in regions with lax regulations, have been found to contain PFAS either as active ingredients or impurities. Once in the soil, PFAS can alter microbial communities, interfere with organic matter dynamics, and resist natural degradation processes, thereby threatening long-term soil fertility and contaminating groundwater systems [151]. Their presence raises critical questions about the adequacy of current regulatory frameworks and the need for enhanced monitoring and risk assessment for persistent contaminants in agroecosystems.

6. Sustainable Management Strategies

Sustainability in pesticide and soil management refers to the implementation of practices that maintain or enhance soil fertility, minimize environmental contamination, and support long-term agricultural productivity while remaining economically feasible for farmers. The goal is to reduce the negative impacts of conventional pesticide use, such as soil degradation, biodiversity loss, and water contamination, by promoting integrated, environmentally friendly alternatives. The following strategies aim to achieve this by improving soil microbial activity, enhancing organic matter retention, reducing toxic residue buildup, and fostering ecosystem resilience. Collectively, these approaches contribute to healthier soils, safer food systems, and more cost-effective, long-term solutions for pest control and soil restoration.

6.1. Bioremediation and Microbial Inoculation for Pesticide Degradation

Biodegradation and bioremediation are related processes based on microbial transformation or metabolism of pesticides. The difference between the two is that biodegradation occurs naturally, while bioremediation is a technology-driven process. Bioremediation involves the in situ utilization of microorganisms to degrade pesticides. Bioremediation requires efficient microbial strains capable of degrading significant pollutants to minimum concentrations. Achieving an adequate biodegradation rate in a limited time frame is essential for reducing pesticide residues and their metabolites to a considerable level. Moreover, the variables that impact the rate of biodegradation in soil include pesticide availability to the microbes, microbial physiological conditions, the rate of survival of microbes at the contaminated site, and the maintenance of a stable microbial population. The successful bioremediation process depends on the specific niches so that they can be exploited successfully. However, certain factors limited the understanding of pesticide-degrading microbial population dynamics, including temperature, pH, moisture, nutrients, and pesticide concentrations [150]. Moreover, bioremediation and physicochemical remediation are considered a suitable strategy to reduce the risk of pesticides. For example, the use of biochar immobilization and adsorption using biochar, biological adsorbent-mediated physical techniques, functionalized modified absorbent, and electrochemically assisted soil washing and flushing techniques showed significant results for pesticide removal [151].

6.2. Use of Biochar and Organic Amendments to Enhance Soil Resilience

Various studies have been conducted on the influence of biochar application on crop yield [152]. Recent research has shown that the pyrolysis of biomass with minerals and the addition of post-treated biochar, either by oxidation or by adding minerals, can improve crop yield [153]. Biochar is a solid product enriched with carbon, produced by pyrolysis in which biomass is heated above 250 °C in an inert environment [154]. The carbon content and the porous structure of biochar make it an ideal candidate for numerous applications, including water treatment and soil amendment, where high carbon content and large surface area for adsorption are required [155]. Moreover, some typical biochar applications include being used as a sorbent or in various oxidation processes to degrade multiple environmental pollutants, such as heavy metals (As, Cu, and Cd) [156] and complex organic pollutants, such as dyes and pesticides [157]. Many measures have been taken to enhance the soil properties, including using additives, which have recently gained attention [158]. Maintaining soil quality is essential for promoting sustainable agriculture and ecosystems [159]. Various approaches to improve soil quality, including cover crops, tillage practices, and crop rotation, [160] by applying soil amendments [161,162]. The soil amendments further divide into two main categories: (a) organic materials, such as biochar, straw, pomace, seaweeds, leaves, manure, sawdust, and compost; (b) inorganic materials, including sand, gypsum, vermiculite, zeolite, and lignite [163]. Both types enhance soil properties and C sequestration, restore saline and crop yields, and improve fertilizer effectiveness [152]. From an economic standpoint, organic amendments are gaining attention due to the increasing cost of inorganic fertilizers. This enhances soil health and reduces reliance on synthetic fertilizers [164]. These remediation technologies include different amendments, such as rice husk, fruit peel, dead leaves, tree bark, and biochar, which are capable of transforming or immobilizing pesticides and other pollutants [165].

6.3. Development of Eco-Friendly and Biodegradable Pesticides

Eco-friendly or green pesticides represent a major shift from traditional chemical-based pesticides. The difference between these two types of pesticides lies in their chemical composition as well as in their operational ethics [153]. Eco-friendly pesticides have been developed to minimize the ecological impacts and risks to human health. These pesticides can be derived from many sources, such as plant extracts, microbial agents, marine by-products, and minerals, and have less impact on the surrounding environment. The best example of eco-friendly pesticides is microbial pesticides, which are pathogen-specific to the pest, resulting in minimal or no harm to other species. The most common example is Bacillus thuringiensis (Bt), which produces a toxin that is toxic to some insects and their larvae, such as caterpillars, beetles, and fly larvae, but remains non-toxic to other fauna [166]. Furthermore, biochemicals such as pheromones produced by various plant species interfere with insect mating, and aromatic plant extracts attract the insects to a trap [153]. Moreover, many plants produce pesticidal substances, which are plant-incorporated protectants (PIPs) against pests. Scientists can use these genes to produce GMOs that can reduce the dependence on chemical pesticides [154]. Additionally, essential oils, which are concentrated liquids, are also reported to kill or repel insects because of their strong volatile aroma, including oils from plants like eucalyptus, citronella, and peppermint [167]. Furthermore, diatomaceous earth is a fine powder prepared from fossilized algae with hard shells, used to kill pests such as bugs, cockroaches, and other insects [156].

6.4. Integrated Pest Management (IPM) to Reduce Pesticide Dependency

Integrated pest management is a sustainable approach to controlling pests through the combination of techniques used as a key strategy that complements or is an alternative to synthetic pesticides. Over the past two decades, global pesticide application has increased to 3.5 billion kg/year, amounting to an international market valued at $45 billion. However, the cost of pesticides ranges from $4 to $19 per kg of active ingredient applied, highlighting the potential benefit of the IPM approach, which reduces pesticide dependency and helps to protect both the environment and human health while supporting agriculture and farmers [168]. The effectiveness of IPM relies on the principle of using a variety of complementary methods to control pests, weeds, and diseases. IPM also describes multiple tactics for managing various pests in ways that are both ecologically and economically sustainable [128]. IPM strategies included substituting pesticide compounds, which were carefully and selectively replaced with safer alternatives whenever possible. For instance, Azardirachta indica, a natural pesticide, belongs to the family Meliaceae and serves as a highly potent bio-pesticide [169]. Furthermore, developing plant varieties with pest resistance genes is important because natural resistance traits sometimes are lost when breeding focuses on yield traits [170]. Moreover, the biological control of pests using predators or parasitoids includes the use of the parasitoid wasp (E. lopezi) to control cassava mealybug in Asia and Central Africa. Furthermore, in China, pests include diamondback moths, cabbage white butterflies, and aphids, which are being controlled by the IPM techniques, cutting pesticide use by 20–70% [169]. The use of pheromones is another important IPM method to control various pests. For instance, the use of pheromone traps with a small amount of dichlorvos pesticide in recycling bags or jars reported a more than 40% increase in yield, followed by a decrease from 15 sprays to zero per season [168].

6.5. Policy and Regulatory Frameworks for Sustainable Pesticide Use

Effective policy and regulatory frameworks are essential for promoting the sustainable use of pesticides and minimizing their long-term impacts on soil fertility and environmental health. These frameworks should enforce strict guidelines on pesticide registration, usage limits, and approved application methods, ensuring that only environmentally safe and scientifically evaluated products are used. IPM approaches, supported by regulatory bodies, can encourage reduced reliance on chemical pesticides through the adoption of biological controls and cultural practices. Moreover, regulations should mandate monitoring of pesticide residues in soil and water, promote transparency in reporting, and incentivize the development and adoption of eco-friendly alternatives [114]. To develop efficient and effective policies at the national level, the government needs to prioritize specific targets to quantify the environmental and health risks and set transparent monitoring and reporting of data on these potential risks [171]. By aligning agricultural practices with sustainability goals, robust policy frameworks can help safeguard soil ecosystems and ensure long-term agricultural productivity.

7. Future Research Directions

7.1. Need for Long-Term Field Studies on Pesticide Degradation and Soil Health

The concerns regarding soil health are linked to both current and future needs. Proper soil health management can enhance agricultural productivity and profitability while ensuring long-term sustainability [172]. Due to divergent research findings reported in the literature, it is challenging to determine how pesticides impact the soil environment. Therefore, it is difficult to find a definite conclusion about the overall impact of pesticides since different groups of pesticides represent diverse variations in toxicity. Similar uncertainties are associated with the effect of pesticides on nutrient cycling, soil microbial communities, soil enzymes, and biochemical processes. Moreover, other factors also influence how pesticides affect soil characteristics, including pesticide concentration, type, chemical activity, and nature of metabolic products formed during breakdown. Additionally, long-term and repeated exposure to pesticides may also disturb chemical equilibrium and potentially reduce the productivity and fertility of the soil. Furthermore, the molecular responses of soil microbes to pesticide exposure could help to gain a deeper understanding of how these chemicals affect microbial diversity, enzymatic activities, and biochemical reactions. In contrast to traditional methods, future research should be based on advanced molecular techniques for better quantitation and understanding of the overall impact of pesticides on soil biochemistry and health [173]. Thus, long-term field studies are crucial to fully understand the cumulative effects of pesticide degradation on soil health and fertility. Most current research focuses on short-term laboratory experiments, which may not capture the complex interactions between pesticides, soil components, and environmental variables over time. Extended field studies can provide insights into how pesticide residues and their metabolites influence microbial communities, nutrient cycling, soil structure, and organic matter dynamics under real-world agricultural conditions. These studies are essential for identifying subtle, gradual changes in soil quality and for developing accurate risk assessments and sustainable management practices. Ultimately, long-term data will support evidence-based policymaking and guide the development of safer, more sustainable pesticide use in agriculture.

7.2. Advances in Biotechnology for Enhancing Microbial Pesticide Breakdown

Microbial consortia are tremendously capable of degrading pesticides in soil and water. In recent days, due to the enhancement in biotechnological techniques, it has been possible to enhance the desired functions of microbial consortia. A single strain cannot degrade a variety of pesticides. The solution is to utilize the mixed culture, which offers a comprehensive solution to achieve faster and comprehensive degradation, and technological advancements allow the synthetic microbial strains to achieve quicker and more comprehensively, according to the design steps. Moreover, these microbial strains work synergistically and can break down pesticides more efficiently without negatively impacting the environment. Looking ahead, more detailed studies are needed to understand the functionality and diversity within microbial consortia. Furthermore, developing a database that catalogs the nutritional requirements, metabolites, and enzyme functions can be helpful for designing consortia with unique capabilities [174]. Additionally, post-genomics microbial methods could offer deeper insight and improved assessment of microbial communities during bioremediation [175]. These post-genomic methods include advanced molecular techniques such as metabolomics, transcriptomics, genomics, and proteomics that can be used to explore the microbial genetic makeup, mode of action, and degradation pathways that may develop as a result of exposure to different groups of pesticides in the environment [176].

7.3. Development of Predictive Models for Pesticide–Soil Interactions Under Climate Change Scenarios

The application of effective pesticide risk assessment and management plans is vital to minimize the impact of climate change [177]. For risk assessment and management, simulation models are used to assess pesticide transportation and human and environmental risks associated with current conditions [178]. These models are efficient tools to determine the interaction between pesticide properties and specific site conditions [179]. For example, deterministic modeling approaches generate a single outcome based on input relationships and without including any randomness to predict pesticide levels for both research and regulatory purposes under current climate situations [180]. Another approach is probabilistic modeling, which is widely used to determine the natural variability in pesticide behavior and the uncertainties associated with soil modeling, weather, and pesticide data. The probability distribution incorporates the chance of different variables to represent the likelihood of different variable combinations and their resulting outcomes [181]. These two models are used alongside the pesticide health risk data to quantify the potential risk arising from pesticide usage under recent climate conditions [182]. Although significant research has been conducted to identify key climate change factors, limited work has been performed to modify fate and risk models to measure how these variations affect the environment and human health risks arising from pesticide applications [183]. So far, most pesticide fate and risk models only provide estimates based on current conditions. They do not provide any insight into how pesticides are exposed, and the health risks could change with different climate conditions [184].

7.4. Assessment of Alternative Pest Control Strategies with Minimal Environmental Impact

The primary and sustainable goal of agriculture is to reduce the dependency on inorganic pesticides. To achieve these targets, environment-friendly and effective approaches should be developed to manage the dominant pest population under control [185]. Due to the potentially harmful effects of pesticides, farmers have adopted many alternative pest control strategies, such as crop rotations, cultural and mechanical methods, and natural pesticide practices, to decrease their dependency on chemical pesticides and improve food safety and environmental protection [186]. Moreover, recent studies have increasingly focused on assessing alternative pest control strategies, such as modeling-based studies that determined the suitability of non-conventional pest control strategies. For instance, a recent modeling study determined the effectiveness of three non-conventional pest control techniques, such as green insecticide, mating disruption, and the removal of infected plants, to minimize disease spread and manage pest populations [75]. They developed a model to determine plant–insect and pathogen interactions by applying optimal control theory. The findings revealed that all three methods significantly reduced the pest population. However, a cost evaluation shows using green insecticides with the removal of infected plants was the most efficient strategy in cutting potential crop losses from 65.36% down to only 6.12% [75].

7.5. Integration of Omics, Biosensors, and AI-Based Modeling in Pesticide Management

Recent advancements in high-throughput molecular techniques and computational tools have opened new avenues for studying pesticide–soil–microbe interactions at an unprecedented resolution. Omics approaches, including metagenomics, transcriptomics, proteomics, and metabolomics, offer powerful insights into microbial community responses to pesticide exposure, enabling the identification of key genes, pathways, and microbial taxa involved in degradation [187]. These tools can enhance the understanding of functional shifts in soil microbiota and help design tailored bioremediation strategies. Simultaneously, biosensors, based on microbial, enzymatic, or nanomaterial platforms, have emerged as valuable tools for real-time detection of pesticide residues and monitoring degradation dynamics in situ [188]. Their sensitivity, portability, and speed make them especially useful for field-level environmental monitoring. In parallel, artificial intelligence (AI) and machine learning (ML) algorithms are increasingly being applied to develop predictive models for pesticide fate, degradation rates, and environmental impact [189]. By integrating diverse data sources such as pesticide chemistry, soil characteristics, weather patterns, and microbial activity, AI-driven tools can enhance decision-making in precision agriculture and pesticide risk management. Together, these emerging technologies have the potential to revolutionize pesticide monitoring, enhance degradation strategies, and support the development of more sustainable and resilient agricultural systems.

7.6. Soil Carbon Modeling for Future Studies

For future studies, soil carbon modeling is highly recommended to investigate the fate of pesticides in the environment and their impacts on human and animal health. These models are beneficial for determining the long-term changes in soil organic carbon (SOC) dynamics in response to pesticide applications. Indirectly, pesticides can influence the SOC by changing the soil microbial activities and enzyme expression. Furthermore, pesticides can impact the soil carbon by integrating into the soil carbon pool. The modeling tools are used to predict changes in soil organic carbon, e.g., the Rothamsted Carbon Model, which is helpful to validate long-term field studies. Meanwhile, CENTURY, DayCent, and DeNitrification-De-Composition (DNDC) are useful for monthly or daily scale studies [190]. In conclusion, soil carbon modeling provides a robust framework for assessing the long-term ecological implications.

8. Conclusions

Pesticide degradation in soil is a double-edged sword; while essential for reducing toxic residues, its by-products can disrupt microbial balance, hinder nutrient cycling, and degrade soil health. While degradation helps in reducing the persistence and toxicity of pesticide residues, it often leads to the formation of intermediate by-products that may disrupt soil microbial communities, alter organic matter decomposition, and interfere with key nutrient cycles such as nitrogen, phosphorus, potassium, and essential micronutrients. These changes can negatively impact soil structure, water retention, and overall soil fertility, ultimately reducing crop productivity and threatening ecosystem stability. A shift toward sustainable management practices, informed by robust research and regulatory oversight, is essential to safeguard soil fertility, agricultural productivity, and ecological integrity in the face of growing global food demands.