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Impact of Pesticides on Soil Microbial Diversity, Enzymes, and Biochemical Reactions
Abstract
Pesticides are extensively used in agriculture as a part of pest control strategies. Owing to their xenobiotics characteristics, pesticides may adversely affect the proliferation of beneficial soil microorganisms and their associated biotransformation in the soil. Inactivation of nitrogen‐fixing and phosphorus‐solubilizing microorganisms is observed in pesticide‐contaminated soils. Recent studies show that some pesticides disturb molecular interactions between plants and N‐fixing rhizobacteria and consequently inhibit the vital process of biological nitrogen fixation. Similarly, many studies show that pesticides reduce activities of soil enzymes that are key indicators of soil health. The applied pesticides may also influence many biochemical reactions such as mineralization of organic matter, nitrification, denitrification, ammonification, redox reactions, methanogenesis, etc. However, a few reports reveal some positive effects of applied pesticides on soil health. In this chapter, we attempt to analyze the impacts of pesticides on soil microbial communities, soil biochemical reactions, and soil enzymes.
... Einfluss auf die Mikroorganismen an der Wurzeloberfläche nehmen generell Boden-und Pflanzenbehandlungen, wie beispielsweise die Anwendung von Pestiziden (Clark, 1949;Hage-Ahmed et al., 2019). Pestizide werden vorwiegend in der Landwirtschaft eingesetzt, um Ernteausfälle vorzubeugen und können sich über die Atmosphäre, den Boden sowie Wasser in Gebieten verteilen, in denen sie nicht appliziert wurden (Brühl et al., 2021;Gavrilescu, 2005;Grube et al., 2011, Hussain et al., 2009. Die Art und Distanz der Verbreitung von Pestiziden ist abhängig von ihrer chemischen Zusammensetzung und den damit einhergehenden Eigenschaften (Gavrilescu, 2005;Hage-Ahmed et al., 2019). ...
... Pestizide werden zumeist indirekt in den Boden eingetragen. Durch Überschwemmungen können Pestizide in terrestrische Ökosysteme transportiert werden und sich dadurch auf die Mikroorganismendiversität im Boden auswirken, indem sie den pH-Wert des Bodens sowie die Verfügbarkeit von Nährstoffen und Schwermetallen beeinflussen (Hussain et al., 2009;Marschner et al., 2003;Prashar & Shah, 2016;Schulz et al., 2015). Somit ergeben sich veränderte Lebensbedingungen, die sich auf die Diversität von Mikroorganismen im Boden auswirkt. ...
... Somit ergeben sich veränderte Lebensbedingungen, die sich auf die Diversität von Mikroorganismen im Boden auswirkt. In belasteten Böden wird häufig eine Inaktivierung von Stickstoff fixierenden und Phosphor solubilisierenden Mikroorganismen beobachtet sowie eine Hemmung der molekularen Interaktion zwischen Pflanzen und Stickstoff fixierenden Rhizobakterien (Hussain et al., 2009;Prashar & Shah, 2016). Auch die relative Häufigkeit von Archaeen sinkt beim Einsatz von Pestiziden (Karas et al., 2018). ...
In an age in which humans are intervening heavily in aquatic ecosystems, it is of great importance to know the possible consequences for riparian areas in order to derive options for action for nature conservation, species protection, policy, etc.. Microorganisms must also be considered, as a change in their diversity can have far-reaching bottom-up effects on trophic cascades. Water-land effects are generally less well studied than terrestrial inputs into water bodies. In a mesocosm experiment, a plant community of four typical riparian species was treated with different stressors (pesticides, flooding, flooding + pesticides). The pesticide mix consisted of 32 substances of the classes fungicides, herbicides and insecticides and was used in a concentration that could actually be measured in the field. Flooding was carried out via waterlogging for two 7-day periods. The consequences for the fungal community in rhizosphere soil and roots of Epilobium hirsutum compared to controls were evaluated by metabarcoding. In a first PCR the target region (Internal Transcribed Spacer, ITS, 2) was amplified and in a second PCR the samples were individually marked by indices. The establishment and optimization of the methodology represents the core result of the present work, as the results of the sequencing were not yet available at the time of submission. Possible results were discussed based on the current state of research. For example, current research results indicate that fungal diversity is reduced by using pesticides. In addition, a dominance of Asco- as opposed to Basidiomycota can be observed with low-dose pesticides. The influence of pesticides on arbuscular mycorrhizal fungi and endophytes, on the other hand, has not been conclusively clarified. In general, there are very controversial results regarding the effects of pesticides on the fungal community. Flooding showed a tendency for arbuscular mycorrhizal fungi to decrease, whereas saprotrophic fungal species and endophytes increased. Other studies, on the other hand, showed that Mucoromycota, most of which have a saprotrophic lifestyle, were decreasing. The combination of the two stressors can lead to a change in diversity and the dominant ecological strategy, as several factors interact here that can offset or reinforce each other.
... This becomes even more significant in the agro-ecosystems, where the variation in soil microflora may have long term effects on the soil health as well as crop productivity. The environmental factors like the pH, temperature, moisture content, availability, and concentration of nutrients etc., play important role in impacting the microbial population as well as diversity (Hussain et al., 2009). However, with more and more human interventions in almost all ecosystems, the anthropogenic effects on the microbes are becoming even more significant.With modernization of agriculture,a lot of chemicals,especially the man-made chemicals have been in use in the form of insecticides, herbicides, acaricides, nematicides, etc. (or the broadly used term pesticides). ...
... While the reduction in microbial population or their activity can be easily explained due to the toxicity of the pesticides or their derivatives, it may be a bit surprising to observe the positive response of some microbes to application of pesticides (Johnsen et al., 2001). The stimulatory effect of pesticides may be attributed to microbes using them as energy or nutrient source or it may be because the pesticides reducing the competition among microbes by elimination of certain groups of microbes (Hussain et al., 2009). ...
... Certain microbial groups are more susceptible towards interaction of pesticides along with other compounds in comparison to application of an individual pesticide, as also observed by Hussain et al. (2009), where butachlor was used in combination with cadmium. Functioning of soil microbiome was disrupted by other herbicides combined with chemical fertilizers and heavy metals (Chen & Dixon, 2007;Datta et al., 2017;Mishra & Wimmer, 2017). ...
... En cuanto al impacto ambiental, se ha podido observar que puede tener efectos en la composición de la tierra y en diversos procesos bioquímicos asociados a los propios cultivos, afectar metabolismos de especies cercanas y ciclos biogeoquímicos (Riah et al, 2014). Existen efectos a nivel de diversidad microbiana, al alterar el comportamiento y su fisiología, ya que, dependiendo de los organismos presentes, para algunos puede ser tóxico, mientras que otros pueden sobrevivir sin ser -en apariencia-perjudicados (Hussain et al, 2009;Johnsen et.al, 2014). Por otro lado, pueden existir efectos en la composición del suelo, ya que pueden afectar procesos de mineralización de materia orgánica, ciclos del nitrógeno y enzimas presentes. ...
... et.al, 2014). Por otro lado, pueden existir efectos en la composición del suelo, ya que pueden afectar procesos de mineralización de materia orgánica, ciclos del nitrógeno y enzimas presentes. Estas últimas pueden ser activadas o desactivadas generando efectos en la fertilidad, en el equilibrio biológico, y en la contaminación global de la tierra (Hussain et. al, 2009, Kinney et al, 2005, Niewiadonska, 2004. ...
El Clorpirifós (CP) es un insecticida organofosforado de amplio uso en la agricultura, con efectos adversos en el medio ambiente y la salud humana. Su biodegradación mediante la enzima lacasa fúngica ha sido propuesta como una estrategia viable, aunque puede generar metabolitos más tóxicos, como Clorpirifós-Oxon (OX).
Se evaluó el crecimiento de hongos filamentosos (Penicillium sp.) y de pudrición blanca (Pleurotus eryngii y Pleurotus ostreatus) en medio sólido Czapek con altas concentraciones de CP. Tras 15 días, solo Penicillium sp. mostró desarrollo, con áreas de crecimiento de 63,62 cm², 18,7 cm² y 10,5 cm² a 0, 50 y 300 mg/L de CP, respectivamente. A menores concentraciones (10 mg/L de CP), P. eryngii alcanzó 0,19 cm² y Penicillium sp. 8,55 cm², mientras que P. ostreatus no creció.
En cultivos líquidos de Penicillium sp. en medio Czapek, se observó degradación de CP con formación de OX, obteniéndose residuos de 12,1 µg/L y 6,5 µg/L, con una degradación del 14% por día. No se detectó actividad enzimática de lacasa, sugiriendo que la degradación puede involucrar otras enzimas no estudiadas. Por otro lado, la lacasa comercial de Aspergillus sp. no se desestabilizó con CP tras 4 horas a 25°C, mostrando una degradación del 5% por hora y un aumento del OX del 5,7% por hora.
Estos resultados confirman que la biodegradación de CP mediante enzimas fúngicas es viable, aunque con la generación de OX. Se recomienda explorar sistemas alternativos para evitar la formación de este metabolito tóxico.
... Closely linked to oxidation-reduction processes, microbial dehydrogenases are pivotal enzymes in the biological oxidation of soil organic matter [20]. These enzymes are sensitive to anthropogenic contamination/pollution (including the application of herbicides), serving as pertinent bioindicators of soil health [60]. ...
... In general, the application of the herbicides significantly increased the activity of soil Deh and Ure [31]. In this context, it is important to mention that Deh play a critical role in soil microbial metabolism, specifically in the oxidation of organic matter and the transfer of hydrogen to electron acceptors such as NAD + , NADP + , or FAD [20]. These enzymes are involved in key biochemical processes that are essential for maintaining soil health and fertility [60,61]. ...
Nicosulfuron, despite being a post-emergence herbicide commonly used in corn crops to combat weeds, there is still little information on nicosulfuron toxicity for soil microbiota. Little information exists on the impact of nicosulfuron on the enzymatic activities of soil dehydrogenases (Deh), urease (Ure), catalase (Cat), and alkaline phosphatase (Alp). We used a multiple dose- and time point (7, 14, 21, and 28 days) study design to determine the effect of nicosulfuron on these parameters during the first 28 days post-application. The soil pH, electrical conductivity (EC), organic matter content (OM), water content, ammonium-nitrogen (NH4-N), nitrate-nitrogen (NO3-N), and available phosphate were also monitored. Ure was the most responsive enzyme to nicosulfuron. This herbicide exerted a transitory dose- and time-dependent inhibitory effect on Deh activity; maximum inhibition occurred at 14 days at doses from the normal recommended dose onward. For Ure, the maximal inhibitory effect started at 7 days of exposure to half the normal recommended dose and continued for another 14 days. The effect on Cat occurred later, whereas Alp activity was affected by nicosulfuron between 7 and 21 days but only for triple the normal recommended dose. OM showed the most consistent relationships with these parameters, being strongly positively correlated with Deh, Cat, and Alp activities. These results indicate that nicosulfuron may alter the soil metabolic activity, thus affecting its fertility.
... Los resultados de las pruebas de Kruskal-Wallis (Tabla 3) y Dunn (Tablas 4 y 6) mostraron diferencias significativas en las medianas de tiempo de detección de la biomasa por el Multiskan y biomasa total entre los tratamientos con y sin cipermetrina, lo cual respalda la hipótesis de que la presencia del insecticida afecta negativamente el crecimiento bacteriano (Hussain et al., 2009). ...
... Brazilian Journal of Animal and Environmental Research, Curitiba, v.7, n.3, p. 1-19, 2024 a la reducción de la actividad enzimática y los procesos bioquímicos esenciales(Hussain et al., 2009;Zhao et al., 2022).Desde una perspectiva más amplia, estos hallazgos resaltan la importancia de considerar las implicaciones ecológicas de la tolerancia observada a bajas concentraciones de cipermetrina y el potencial de B. subtilis destacando que esta bacteria es solo una de las muchas especies presentes en el suelo entre las que también se pueden encontrar otras con potencial biodegradador como Pseudomonas, Ochrobactrumhaematophilum, Rhodococcus entre otros(Akbar et al., 2015), sin embargo concentraciones muy altas podrían alterar en el crecimiento de las mismas y tener consecuencias más amplias en la dinámica del ecosistema del suelo.En términos de gestión de plaguicidas, nuestros resultados enfatizan la necesidad de adoptar prácticas que minimicen el impacto ambiental, especialmente dado el papel esencial de los microorganismos del suelo. Los efectos negativos observados en cepas como B. subtilis destacan la importancia de buscar estrategias alternativas y ecológicas para el control de la presencia de cipermetrina en el suelo. ...
La utilización masiva de insecticidas como la cipermetrina, en entornos urbanos y agrícolas ha generado preocupaciones debido a su persistencia en el suelo y su potencial daño a organismos no-objetivos. A pesar de su toxicidad y durabilidad de estos productos, algunas bacterias, como Bacillus subtilis, han demostrado tener vías catabólicas capaces de utilizar la cipermetrina como fuente de carbono y energía. En este contexto, el presente estudio se centró en la evaluación general de la tolerancia de B. subtilis, una cepa aislada en Paraguay, a diferentes concentraciones de cipermetrina de uso doméstico y bajo condiciones controladas no reportadas aún en el país para tales propósitos. La investigación destacó cómo diferentes concentraciones de cipermetrina influyeron en la cinética de crecimiento de B. subtilis y cómo estas se correlacionaron entre sí. Los resultados indicaron una notable disminución en el crecimiento bacteriano a concentraciones más altas de cipermetrina, señalando una adaptación reducida de la bacteria a medida que la concentración del insecticida aumenta. Este hallazgo tiene implicaciones significativas, en la comprensión de la adaptabilidad de una cepa nativa y en la estandarización de métodos biotecnológicos con fines ecológicos aplicables para la gestión adecuada de residuos de cipermetrina.
... Co-contamination of the environment with pesticides and heavy metals is a significant issue due to their synergistic cytotoxic effects (Olaniran et al., 2013). The isolated effects of pesticides on soil enzymes are unclear because of their complex behavior and intricate microbial and biochemical interactions in the soil (Hussain et al., 2009). However, prolonged pesticide use disrupts the biochemical balance and reduces soil fertility and productivity (Hussain et al., 2009). ...
... The isolated effects of pesticides on soil enzymes are unclear because of their complex behavior and intricate microbial and biochemical interactions in the soil (Hussain et al., 2009). However, prolonged pesticide use disrupts the biochemical balance and reduces soil fertility and productivity (Hussain et al., 2009). Given the high positive correlation between soil pesticide residues and heavy metals (Avellaneda- Torres et al., 2022;Tariq et al., 2016), heavy metal effects are sometimes monitored to assess pesticide impacts on soil (Olaniran et al., 2013;Tariq et al., 2016). ...
Soil contamination by heavy metals (HM) from pesticides poses a serious environmental threat, affecting sustainability and agricultural productivity. Soil enzymes are essential for biochemical reactions such as organic matter decomposition and nutrient cycling and are vital for maintaining soil health. However, the effects of HM on soil enzyme activity are not yet well understood. This study examined the impact of HM contamination on enzymatic stoichiometry in regions with intensive pesticide use. We selected flower cultivation areas with 5 years (CA1) and 10 years (CA2) of pesticide exposure and a native forest area (NFA) as a reference during the dry and rainy seasons. We measured Cd, Cu, Mn, Pb, and Zn levels and employed ecological risk indices to assess contamination levels. We also analyzed enzyme activities (arylsulfatase, β-glucosidase, acid phosphatase, urease) and enzymatic stoichiometry. CA2 exhibited the highest concentrations of Cd, Cu, and Mn in both periods, while Zn was highest in both CA1 and CA2. CA2 had higher values for all indices, indicating significant contamination. Compared with NFA, arylsulfatase activity was lower in cultivated areas during both periods, suggesting decreased soil quality. We found negative correlations between Cu, Mn, Zn, and arylsulfatase, as well as a reduction in urease with Cd; these elements also increased microbial C limitation. Our findings show that continuous pesticide input increases HM levels and that enzyme activity and stoichiometry are effective bioindicator of soil contamination. This study underscores the urgent need for guidelines to protect soils from prolonged HM buildup.
... Numerous insecticides may remain in the soil for a long time, years, or even decades (Navarro et al., 2007;Cabidoche et al., 2009;Hladik et al., 2018). Processes including mobilization, immobilization, bioavailability, and transport are significantly affected by the build-up of insecticides in organo-mineral components of complex structures (Gevao et al., 2003;Piccolo et al., 1998;Hussain et al., 2009). The microbial diversity, biochemical processes, and enzymatic activity are changed by the degraded insecticides (Hussain et al., 2009;Munoz-Leoz et al., 2011). ...
... Processes including mobilization, immobilization, bioavailability, and transport are significantly affected by the build-up of insecticides in organo-mineral components of complex structures (Gevao et al., 2003;Piccolo et al., 1998;Hussain et al., 2009). The microbial diversity, biochemical processes, and enzymatic activity are changed by the degraded insecticides (Hussain et al., 2009;Munoz-Leoz et al., 2011). There is always a potential that these xenobiotic compounds will enter different food chains and food webs because soil bacteria typically find them difficult to digest, which could lead to bioconcentrationand bioaccumulation (Maurya and Malik, 2016;Dureja and Tanwar, 2012;Edwards and Bohlen, 1992;Paoletti, 1999). ...
Collembola or springtails are considered to be good model organisms for determining ecological toxicity and are used as non-target bio-indicators in environmental assessments. The susceptibility of these micro-arthropods to different edaphic perturbations is remarkable. One significant element leading to the degradation of soil quality in modern times is the indiscriminate use of insecticides in agricultural fields. Even while using insecticides in agriculture might be profitable, the harmful consequences of these chemicals affect not just the targeted pests that are intended to harm but also a variety of important soil fauna. The adoption of sustainable farming methods is the key to cultivating and conserving a diversified soil community, which plays critical roles in supplying functions and services throughout ecosystems. The goal of this review is to thoroughly explain the negative effects of insecticides on these vital micro-arthropods. An examination of the effects of several insecticides on various Collembola species reveals that collembola is among one of the most vulnerable soil fauna to insecticide contamination. This susceptibility endangers these organisms' well-being and emphasizes the significance of recognizing their ecological responsibilities in the context of sustainable agricultural management.
... The nutrient status of soil, microbial carbon biomass, and non-target biota are disturbed by the impact of various pesticides. They also affect the soil enzymes such as urease, dehydrogenase, nitrate reductase, oxidoreductase, and hydrolyses (Wang et al. 2006;Hussain et al. 2009). ...
... The effects of herbicides on soil microbiota depend on concentration, degradability, adsorption, desorption, persistence, bioactivity, and toxic dosage level. Some microbes which can withstand a single application (Butachlor) are more sensitive to combination (Butachlor with cadmium) (Hussain et al. 2009). The inorganic fertilizers combined with heavy metals suppress soil microbial activities, and secondary metabolites produced by the transformation of herbicides are more severe than direct effects. ...
Nanotechnology is an emerging technology that combines materials science and engineering fundamentals, altogether synthesizing materials at the nanoscale to solve various current problems. Agrochemicals are often used in modern intensive agriculture to protect crops from biotic stress, provide vital nutrients, and boost millet growth and yield. Although they are beneficial in the short term, their long-term and persistent applications damage soil fertility and negatively affect the rhizospheric microbiome. Nanotechnology in the form of nano-based agro-formulations is an innovative, environmentally acceptable, and practical solution for substitute synthetic fertilizers. Nanotechnological formulations and nanoparticles in the form of nanopesticides, nanoherbicides, nanogels, nanofertilizer, and nanofungicides are reported to have efficacy in continuous release of nutrients regulated distribution to plant nutrients very effectively. These nanoformulations helps in fighting phytopathological diseases, promotes plant, and microbiome productivity. In addition, they are effective in alleviating biotic and abiotic stress in crop plants. However, despite their extraordinary effectiveness, they also have several drawbacks, such as a tedious manufacturing process, shaky delivery, and dosage-sensitive effectiveness. Learning and acknowledging the influence of nano-based agrochemicals on highly nutritious crops such as millets is important for further commercialization and wide utilization in agriculture. Hence, this chapter focuses on the usage of nanoformulations on millet crops, their effects on soil rhizospheric communities, and soil fertility.KeywordsNanoformulationsRhizosphereMilletsSoil biotaMillet-grown soils
... Certain herbicides like metsulfuron methyl, chlorsulfuron, and thifensulfuron methyl have been found to inhibit the growth of certain microbial strains [54] which carry out important ecological processes, and hence alternation in the growth and development of these bacteria will ultimately hamper the soil fertility ( Fig. 24.1). The competition between certain groups of microorganisms in the soil can be greatly reduced after the administration of pesticides, which can inhibit the growth of certain microorganisms while accelerating the growth of others [55]. In a study application of endosulfan to the soil resulted in a 76% rise in bacterial biomass and a 47% reduction in fungal biomass [56]. ...
... In a study application of endosulfan to the soil resulted in a 76% rise in bacterial biomass and a 47% reduction in fungal biomass [56]. Pesticides also can activate and deactivate any particular microorganisms or enzymes, thereby influencing principal biochemical reactions occurring in soil like fixation of nitrogen, and formation of nitrite and nitrate [55,57]. Pesticides affect the decomposition rate of organic matter which is a pivotal soil property for ascertaining the microbial cell quality and soil productivity. ...
The advent of pesticides has significantly increased the growth and yield of the crop plant. However, the extensive application of pesticides leads to environmental pollution and reported to harm both both flora and fauna. The continuous accumulation of synthetic chemicals (pesticides)also poses serious risk to human. Farmers who are continuously exposed to pesticides may develop chronic diseases like diabetes, hypertension, and other detrimental ailments. In the present chapter an attempt will be made tooverview the insights of natural compounds synthesized and screeted by different microbes and plants for the biodegradation of pesticised under the following lines: (i) to introduce pesticides and their impacts on sustainability; (ii) to discuss the concerns related to pesticide pollution; (iii) to highlight pesticide toxicity to soil and water ecosystems; (iv) to enlist different types and methods of pesticides bioremediation; (v) to report the enzymes involved in pesticide bioremediation, and (vi) to suggest the future prospective of pesticide bioremediation
... Thus the injudicious and indiscriminate use of pesticides has resulted in tremendous loss to environment and human health. Furthermore, pesticides have also been reported to adversely affect the microorganisms in soil responsible for nitrification 27 . Along with the target, pesticides also affect beneficial soil microorganisms, natural enemies to insect pests, fish, birds and other wildlife, thus adversely affecting the tritrophic interactions, food chains and food webs directly and indirectly. ...
Organic agriculture may be described as an included farming system that strives for sustainability, the
enhancement of soil fertility and organic range whilst, with uncommon exceptions, prohibiting
artificial pesticides, antibiotics, synthetic fertilizers, genetically modified organism. Disease
management strategies in organic farming are Growing disease resistant varieties, Exclusion of
pathogen, Application of organic amendments, Cultural control, Orchard bio-intensification, Physical
methods, Botanicals, essential oils, baking soda, butter milk etc, Application of biocontrol agents,
Application of mineral-based fungicides. Biochemically efficient strain of Pseudomonas fluroescens Pf
IV was found effective. P. parasitica. that, among the tested species of bacteria viz. Bacillus subtilis, B.
polymyxa, Pseudomonas fluorescens are effective
... Panic attacks, cramps, vertigo, blurred vision, nausea, headaches, and skin rashes are a few symptoms of these acute effects, while effects from extended exposure (chronic effects) include effects on reproduction, blood and nerve disorders, genetic alterations, and congenital disabilities [19][20][21]. Similar to this, the decomposition of organic materials in the soil, the modification of the microbial diversity in the soil, the impact of pesticides on some beneficial soil invertebrates, and the percolation of soil layers to ground water all pose a danger to the sustainability of the environment [18,22,23]. Organophosphate pesticide levels have been found in biological matrices such blood serum and urine [17,[24][25][26][27][28], and they have also been found and measured in environmental matrices like soil, sediments, water, and air [29][30][31][32][33][34] in a number of fascinating contemporary investigations. ...
India's pesticide consumption ranks it third in Asia and 12th globally, behind
China and Turkey. For the current study, information on different types of
pesticides, usage trends, and precise pesticide consumption in India and
globally was collected, organised, and summarised. The 1960s brought
pesticides to India, where they remain a staple of the nation's agriculture and
are still widely used. The Indian economy is primarily driven by the
agriculture sector, which employs almost 70% of the labour force.
Nevertheless, in India, the majority of pesticides used are insecticides. Less
than 1% of all pesticides are used worldwide, including in India. Apart from
posing a threat to the environment, an over reliance on pesticides has also been
connected to the presence of organophosphate residues in tea, sugars, fruits,
vegetables, and other agricultural products throughout India. The residues
found in human and animal tissues, blood, milk, honey, and other
physiological fluids are evidence of their excessive use and bioaccumulation
potential. The current study highlights the numerous occasions in which
different organophosphates have been discovered to be over their
corresponding MRL limits. Because some of the discovered organophosphates
are so harmful, the WHO has categorised them into hazardous categories 1a
and 1b. Their intentional or unintentional intake causes serious health impacts
and hundreds of deaths per year. Most of the poisoning cases that are displayed
here were caused by substances consumed during suicidal attempts. This
illustrates how easily these harmful medications might be located on the
market.
... In farmlands, agricultural practices strongly affect soil biodiversity, either directly by reducing organisms' vitality or even by killing them (e. g., the use of pesticides or tillage), or indirectly by modifying soil physical and chemical properties (Campbell et al., 2017;Hussain et al., 2009;Lichtenberg et al., 2017;Tsiafouli et al., 2015). Chemical properties (e.g., soil organic carbon and nitrogen content, pH) and physical properties (e.g., soil compaction and moisture, size of mineral particles) directly influence soil fertility and plant growth (Bronick and al, 2005), which may in turn affect abundance and functional relationships among other taxa (Menta and Remelli, 2020) such as earthworms (Edwards and Arancon, 2022), arthropods, or microorganisms (Coleman et al., 2017). ...
... While pesticides can have negative effects on soil microbes, they can also act as a carbon source for specific groups of microbes. As microorganisms are key indicators of soil health, it is crucial to study the impact of pesticides on them [23]. In order to gain a deeper understanding of how various pesticide treatments affect soil microorganisms, an analysis was conducted on microbial biodiversity, community structure, composition, and function, as well as community networks [24]. ...
The increased use of chlorantraniliprole and fludioxonil has sparked concerns about their residues and impact on the soil microbiome, highlighting an urgent issue requiring attention. This study investigates the residue dynamics of corn after chlorantraniliprole and fludioxonil treatments, as well as their effects on soil enzyme activity and microbial community structure. High-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS) analysis showed a significant decrease in chlorantraniliprole and fludioxonil residues in the soil after combined application, especially with chlorantraniliprole. This application caused a temporary reduction in urease and sucrase activities. Furthermore, high-throughput sequencing of the soil microbiome revealed a decrease in the relative abundance of Talaromyces during fludioxonil application, while Mortierela and Gibberella increased. Additionally, Vicianmibacteraceae and Vicianminbactererales saw significant increases after chlorantraniliprole application. The combined application of chlorantraniliprole and fludioxonil not only decreased the population of harmful microorganisms but also lowered residue levels in the soil when compared to individual applications. This ultimately enhanced the efficacy of control measures and promoted environmental compatibility.
... Their xenobiotic properties may adversely affect the proliferation of essential microorganisms in the soil. Pesticidecontaminated soils have been observed to experience an inactivation of phosphorus-solubilizing and nitrogen-fixing soil microorganisms [4]. Studies and research work in the Nyando River catchment area have shown that the use of pesticides in agriculture leads to pesticide residues levels ending up in the soil [5]. ...
The study assessed the agricultural pesticide residue levels in soil samples from six selected sites along Thiba River catchment area, Mwea Irrigation Scheme, Kirinyaga County, Kenya. The aim was to determine pesticide residue levels in the dry and wet seasons of the year and compare to the set limits by the World Health Organization (WHO). The soil samples were collected in February and May 2021 representing the dry and wet seasons respectively, according to the meteorological department in Kenya and based on the human activities and crops grown in the study area. Chlorpyrifos was the most prevalent pesticide residue detected with levels ranging from 7.38±1.04µg/kg - 213.43±34.75 µg/kg; Lambda- cyhalothrin’s from < 0.005 µg/kg- 13.98 ± 2.02 µg/kg while the levels of Metalaxyl residue ranged from < 0.05 µg/kg - 6.88±0.55 µg/kg in dry and wet seasons. The pesticide residue levels were higher in soil samples in the dry than the wet season. Metalaxyl and Lambda-cyhalothrin residue levels were lower than the set Maximum Residue Levels in soil by the WHO of 50 µg/kg and 20 µg/kg in the dry and wet seasons respectively. The chlorpyrifos pesticide residue levels were higher than the set limits of 10 µg/kg by the WHO except in sites 5 and 6 (upstream) in both the dry and wet seasons.
... Pesticides used in agriculture are artificial in origin and get absorbed in the soil through surface overflow from treated plants 10 . The application of pesticides may threaten aboriginal microorganisms of soil and affect the soil ecosystem, thus entering in food chain and affecting human health (Hussain et al 2009). Pesticides interact with soil microbes and their activities thereby changing the biochemical and physiological behaviour of soil microbes (Singh & Walker, 2006). ...
Agriculture has become the main stay of most growing economies. This has given rise to changes in traditional farming methods. One of such change is in the use of pesticides. Pesticides are substances used inside or outside to prevent, control, repel, or kill insects, plants, fungi, and other pests. Application of pesticides for agricultural production has risen to an alarming level particularly in developing countries often living behind residues which persists in the ecosystem. The mechanism of action of pesticide is aimed at killing pests or rendering them ineffective. However, they can also act upon unintended organisms, such as humans. A number of health issues have been linked with pesticides in the environment. It is against this background that the recent paper attempts to discuss pesticide residue in the soil with a view to providing guidance to pesticide users and policy makers. The paper focuses on classification of pesticides, fate of pesticides in the soil, degradation of pesticides, factors affecting levels of pesticide residue in the soil, health hazards associated with pesticides, present situation of pesticide residue in agricultural soil and way forward.
... Pesticides have been documented to produce toxic effects in humans, including short-term symptoms like headaches and nausea, as well as chronic issues such as cancer, reproductive harm, and endocrine disruption [11][12][13]. On the other hand, pesticide degradation impacts soil microbial diversity, along with metabolic processes and enzyme activity [14,15]. Okra being a fast growing crop is harvested at very short interval (3-4 days) and this practice increases the chance of fruits having high load of residues which can pose health hazards to the consumers [16]. ...
Understanding pesticide residue levels in food items and soil is crucial for ensuring food safety. In this context, a study on persistence and dissipation kinetics of λ-cyhalothrin residues in okra fruits and soil was conducted for two consecutive years. λ-cyhalothrin was applied in okra at the recommended dose (15 g a.i. ha-¹) and double dose (30 g a.i. ha-¹). Okra fruit and soil samples were collected at different intervals after second spray and the residues were estimated using GC-MS/MS. The initial residue level in okra fruits was higher at double dose and declined gradually falling below the limit of quantification (0.01 mg kg-¹) within 7 to 10 days of application. Dissipation followed first-order kinetics, with half-life of 2.17 to 2.43 days. In soil, the initial residues dropped below the limit of quantification within 3 to 5 days of application. Since the initial residue levels in both okra fruits and soil were below the corresponding EU–MRL (0.2 mg kg-1), λ-cyhalothrin can be safely used in okra cultivation.
... The binding of herbicides to active sites of enzymes prevents microorganisms from catalyzing their reactions. This can inhibit growth, slow reproduction, and even cause the death of microorganisms, (Liu et al., 2020) resulting in a reduction in the diversity of the microorganisms (Hussain et al., 2009;Imfeld & Vuilleumier, 2012). A similar reduction in enzymatic activities after the application of treflan, triflurotox, and acetamipyride has also been observed by Wyszkowska et al. (2002) and Yao et al. (2006). ...
A field experiment was carried out during the Rabi 2022–23 at Punjab Agricultural University, Ludhiana to evaluate the effect of pyroxasulfone and pendimethalin on soil enzymatic and microbial activities when applied individually or as a tank mix combination. The experiment employed a factorial randomized complete block design in triplicate encompassing 16 treatments. Control soils exhibited a continuous increase in enzymatic and microbial activities over time. In herbicide-treated plots, a highly dose-dependent lag phase was observed in all enzymatic and microbial activities which gets shorter or disappear at higher application rates. Following the initial lag phase, inhibition in enzymatic and microbial activities was observed with higher inhibition in tank mix combination (90.7 to 99.1% up to 90 days after herbicide application (DAA) followed by pendimethalin (77.3 to 92.9% up to 90 DAA) and pyroxasulfone (30.3 to 76.2% up to 45 DAA). After initial inhibition, enzymatic and microbial activities increased at harvest. Principal component analysis (PCA) revealed that dehydrogenase activity among soil enzymes and bacteria among microbial populations were more sensitive to studied herbicides. Based on the values of the Integrated Biomarker Response (IBRv2), pendimethalin had a greater impact on soil activities than pyroxasulfone, and their combined application exhibited a synergistic effect.
... Thus the injudicious and indiscriminate use of pesticides has resulted in tremendous loss to environment and human health. Furthermore, pesticides have also been reported to adversely affect the microorganisms in soil responsible for nitrification 27 . Along with the target, pesticides also affect beneficial soil microorganisms, natural enemies to insect pests, fish, birds and other wildlife, thus adversely affecting the tritrophic interactions, food chains and food webs directly and indirectly. ...
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... Only 1% of the applied pesticide affects the intended pests and the rest reaches the environment polluting soil, water, and biota. The long-term persistence of these pesticides may directly or indirectly affect soil enzyme activities and physiological characteristics of nontarget soil microflora including plant growth-promoting rhizobacteria, that eventually reduce the performance of several crop plants [10][11][12]. ...
The increased use of organophosphorus pesticides and their persistence in soil pose a great menace to human health, animals, and milieu. Bioremediation can be applied for the degradation of such persistent chemicals. The aim of our study is based on the degradation of the organophosphorus pesticide, Quinalphos in the brand name “Ekalux” by using microorganisms that are already a part of the natural soil microflora. Enterobacter cloacae which have the capacity to degrade quinalphos were isolated from contaminated soil. The pre-isolated strain of E. cloacae (NCBI Accession No: CP035738.1) is used as a biodegradative agent of Quinalphos. The percentage of degradation of quinalphos was identified through a chemical reaction with a DPAAP reagent (diazotized para aminoacetophenone). Several factors can limit the rate of biodegradation such as temperature, pH, glucose concentration, NaCl concentration, and so on. A piece of these factors must be optimized for the secluded organism to achieve optimal degradation of Quinalphos. For biodegradation studies, the isolated organism E. clocae were inoculated into minimal media with Quinalphos. The efficiency of both free cell cultures and immobilized cell cultures was checked along with optimization studies. Immobilized cells were found to give better results than free cell cultures by 9%–15%. 35°C ± 2°C temperature, 6.5– 7.5 pH, and approximately 1% glucose concentration were found to be optimum for the most efficient biodegradation of quinalphos by E. cloacae.
... Although herbicides play an important role in weed management, the active ingredients sprayed on soil have diverse impacts on soil biological properties. Soil enzymes produced by microorganisms are among the active elements responsible for biochemical processes in soil ecosystems [26]. Their activities are sensitive to the soil environment and are related to the quality and productivity of the soil as well as microbiome activity. ...
Background
The herbicide cinmethylin, which was originally registered for use in rice fields, has the potential to control grass weeds in wheat fields before the emergence of wheat. However, its herbicidal activity against various troublesome grass weeds that infest wheat fields in China and its relationships with soil pH, soil enzymes and soil bacteria are not well known. Here, the effects of applying cinmethylin on the soil surface were tested on six grass weeds, and its impacts on soil characteristics, including the soil pH, soil enzymes and bacterial community, were evaluated.
Results
Alopecurus aequalis, A. japonicus and A. myosuroides were highly sensitive to cinmethylin, with GR50 values of 78.77, 61.49 and 119.67 g a.i. ha− 1, respectively. The half-lives of cinmethylin at 1-, 10- and 100-fold the recommended rates were estimated at 26.46 − 52.33 d. Cinmethylin significantly increased the soil pH but decreased the activities of soil sucrase and urease. At 10- and 100-fold the recommended rate of cinmethylin, the bacterial abundance and diversity significantly decreased at 30 and 60 days after cinmethylin treatment. Cinmethylin at 100-fold the recommended rates largely promoted bacterial co-occurrence network complexity. Cinmethylin at high concentrations temporarily inhibited the abundance of the Nitrospira genus, as indicated by the copy numbers of the ammonia-oxidising archaea (AOA) amoA and ammonia-oxidising bacteria (AOB) amoA genes. Further analysis revealed that soil pH was negatively related to soil urease, and a significantly positive correlation was detected between soil urease and soil nitrification.
Conclusion
Collectively, the application of cinmethylin at the recommended field dose had nearly no effect on the soil ecosystem, but its potential risks at high concentrations deserve further attention.
Supplementary Information
The online version contains supplementary material available at 10.1186/s40793-024-00608-y.
... It is known that application of pesticides may impact the structure and functional activities of non-target microorganisms as soil acts as a sink for applied pesticides. Soil comprises of many enzymatic pools of free, immobilized extracellular enzymes, and enzymes within microorganisms (Hussain et al., 2009;Mayanglambam et al., 2005). These enzymes are the key indicators of biological equilibrium (Mandal et al., 2020) as microorganisms and soil enzymes play important role in vital processes, like mineralization, nitrification, and nutrient recycling. ...
Impact of diamides on structure and functional activities of soil microflora and soil health has not been well studied. Effect of chlorantraniliprole and cyantraniliprole on the activity of dehydrogenase, acidic, alkaline phosphatase, amylase, invertase and urease enzymes in chilli planted soil was assessed. Two applications of chlorantraniliprole @ 30, 37.5 and 60 g a.i. ha⁻¹ and cyantraniliprole @ 60, 75 and 120 g a.i. ha⁻¹resulted in adverse effect. Dehydrogenase activity was reduced by 21.34 and 22.07 per cent on 7thday, in double dose chlorantraniliprole and cyantraniliprole respectively. Activity of both acidic and alkaline phosphatase enzyme reduced by 4.98 and1.06 per cent at 5th day after application of chlorantraniliprole and cyantraniliprole @30 and 60 g a.i. ha⁻¹ respectively. On the other hand, amylase and invertase activity showed non-significant reduction and urease enzyme activity was slightly reduced (0.02–3.44%). The recommended doses of these two diamides had short term adverse effect on these enzymes, while higher doses led to 20 -30 per cent reduction in enzyme activity). However, activity of enzymes was restored after some time which could be due to adaptive capacity of soil microbes and dissipation of the pesticide residues.
... Some findings have supported the fact that herbicide residues can serve as a carbon and energy source for microorganisms, while other reports claim that herbicide residues result in devastating effects on soil biology and chemistry. However, in the long term, it may disrupt the soil's biochemical balance, thus reducing soil fertility and productivity (Hussain et al. 2009;Marin-Morales et al. 2013). The active ingredients present in the herbicides affect the nitrite synthesis, nitrogen fixation and mycorrhizal process. ...
... 382.5 and 510 g ha −1 . This was probably due to lethal action of herbicide on soil microbes, reducing their number, activity and consequently, the diversity of their microorganisms (Hussain et al., 2009;Imfeld & Vuilleumier, 2012). After initial inhibition, microbial activity began to recover 45 DAA of pyroxasulfone at 127.5 and 255 g ha −1 and 60 DAA of pyroxasulfone at 382.5 and 510 g ha −1 , and on 90th DAA the microbial activity in soil treated with herbicides varied non-significantly from control soil. ...
This study is to understand the fate and ecological consequences of pyroxasulfone in aridisols of Punjab, a detailed dissipation study in soil, its influence on soil enzymes, microbial count and succeeding crops was evaluated. Half-lives (DT50) increased with an increase in the application rate of pyroxasulfone. Dissipation of pyroxasulfone decreased with increase in organic matter content of soil and was slower in clay loam soil (DT50 12.50 to 24.89) followed by sandy loam (DT50 8.91 to 17.78) and loamy sand soil (DT50 6.45 to 14.89). Faster dissipation was observed under submerged conditions (DT50 2.9 to 20.99 days) than under field capacity conditions (DT50 6.45 to 24.89 days). Dissipation increased with increase in temperature with DT50 varying from 6.46 to 24.88, 4.87 to 22.89 and 2.97 to 20.99 days at 25 ± 2, 35 ± 2 and 45 ± 2 °C, respectively. Dissipation was slower under sterile conditions and about 23.87- to 33.74-fold increase in DT50 was observed under sterile conditions as compared to non-sterile conditions. The application of pyroxasulfone showed short-lived transitory effect on dehydrogenase, alkaline phosphatase and soil microbial activity while herbicide has non-significant effect on soil urease activity. PCA suggested that dehydrogenase and bacteria were most sensitive among enzymatic and microbial activities. In efficacy study, pyroxasulfone effectively controlled Phalaris minor germination, with higher efficacy in loamy sand soil (GR50 2.46 µg mL⁻¹) as compared to clay loam soil (GR50 5.19 µg mL⁻¹).
... The physical adsorption and desorption of pesticides is one of the first process in soils, and it is closely related to the later environmental behaviors, such as runoff, leaching, transformation, and degradation. Numerous factors, such as the characteristics of the soil/the flora and fauna, influence the fate of pesticides, causing them to undergo varying degrees of degradation and the sorption phenomena (Hussain et al. 2009). Enzymatic, biochemical, and microbiological activities in the soil influence the accumulated pesticides (Egbe et al. 2021;Kumar et al. 2021). ...
Ametoctradin fungicide’s ecotoxicological and lithospheric sorption properties have been thoroughly assessed through a variety of experimental techniques that mimic natural environmental circumstances. To achieve this, the current study examined the sorption and degradation of Ametoctradin in 10 different soil samples under carefully monitored laboratory conditions. The negative values of Gibbs-free energy (ΔG), which range from − 15.78 to − 23.56 kj/mol in thermodynamic analysis with a C-type curve are extensively assessed using both linear and Freundlich models. SS5 (soil with highest organic matter) depicted the maximum adsorption (Kd = 41.15 µg/ml), while SS8 (depicting low organic matter content) showed the lowest adsorption extent (Kd = 10.38 µg/ml). GC–MS analysis and UV–visible spectrophotometry were used to evaluate the hydrolytic and photolytic processes involved in Ametoctradin degradation. According to the findings, the hydrolytic and photolytic assays had lowest half-life values of 28.7 and 55.2 days, respectively. Furthermore, the Ametoctradin degradation followed first order reaction kinetics. Soil sample SS6 showed the maximum hydrolytic degradation (57%) due to higher sand content (42%), while SS3 showed the lowest hydrolytic degradation (21%) due to higher silt and clay content. The findings indicated that Ametoctradin exhibited above average binding to the chosen soils, resulting in medium to low persistence as shown by degradation values. Overall, this study offers insightful knowledge about the behavior and fate of Ametoctradin in various soil types, which can help with the creation of practical management plans and environmental risk assessments.
... Moreover, agricultural systems that have high fertilizer input, intensive tillage, and narrow crop rotations can cause decreased soil biota species richness (Brussaard et al., 2007). In addition, the application of pesticides and fertilizers has been found to reduce soil biodiversity as well as increase the emergence of pesticide-resistant pathogens (Hussain et al., 2009). Increased agricultural intensity has also been found to decrease soil biota at higher trophic levels, especially earthworms, enchytraeids, collembolans, and oribatid mites (Brennan et al., 2006;Eriksen-Hamel et al., 2009). ...
... Similarly, Tu (1995) also observed the repressive effect of IC upon the fungal community at about 10 μg active ingredient/gm of soil. Also, the adverse effects of the xenobiotics can be reduced or moderated by some of the environmental factors such as properties of soil, its perseverance, toxicity, amount of xenobiotics present, and its availability to the microorganisms in the soil (Hussain et al. 2009). ...
Urban ecosystem is entirely different from any other ecosystem. With the emergence of urbanization as well as industrialization, xenobiotic, a foreign artificial chemical compound, is introduced in the ecosystem profusely. In human beings, several multitude of proximal tubule cell (PTC) transporters in the kidney import the highly toxic xenobiotic compounds that further change into less toxic products, and this process has an immense role in xenobiotic removal. While higher organisms have a couple of processes to cope up with xenobiotic existence, microorganisms that reside in different urban aquatic bodies have come up with multiple xenobiotic degradative genes. Disposition or degradation of xenobiotics is directly related to the metabolism of this product that further connected to the adaptation of living entity with newly evolved chemical surroundings. In this chapter, we will discuss about different transporters and metabolic genes that are associated with xenobiotic metabolism as well as removal. Upon introduction of xenobiotics from different anthropogenic sources, their transport and metabolism were thoroughly discussed here. From future perspective, this multifaceted discussion about xenobiotic compounds will give new insights to regulate the pathway and will discover more strategy that can detoxify xenobiotics.
... The local water supplies get poisoned as a result of pesticide leaching. For instance, six rivers in Kenya's Lake Victoria catchment area transport contaminants into the lake (Abong'o et al. 2014 The use of pesticides may disrupt the native soil microorganisms and hurt the soil ecology, penetrating the food chain and endangering human health (Hussain et al. 2009;Ogwu et al. 2018;Ogwu 2019). Pesticides interact with soil bacteria and their processes, altering their biochemical and physiologic behavior (Singh and Walker 2006). ...
A rise in the demand for food and other agricultural products is accompanied by an ongoing global population expansion. The need for high yields has led to the development of new-age technologies, which have exponentially expanded the use of chemical fertilizers. Chemical fertilizers, which are primarily composed of elements such as nitrogen, phosphorous, and potassium, are manufactured on a large scale in industrial settings. Modern agriculture makes considerable use of pesticides, which is an affordable technique to increase productivity. However, due to their bio-magnification and persistent properties, pesticide use can have major side effects. As a result of their direct or indirect pollution of the air, water, soil, and environment, several pesticides have adversely affected the health of all living organisms. It is discovered that pesticide reliance is more of a human-made problem with underlying socio-economic and political causes than it is merely a technological issue in the field of natural sciences. Due to potential hazards to the environment and human health, pest control faces challenges on both an economic and ecological level worldwide. It is necessary to fully recognize and understand the numerous, interrelated aspects to address the current worldwide pesticide reliance problem. To address these issues, regulatory and environmental protection organizations in several nations have taken steps to replace synthetic chemicals with biopesticides, which pose fewer or no hazards to the environment and human health. To determine their applicability, this article analyzes many environment-friendly pesticide reduction strategies as well as their economic impact and suitability.KeywordsBiofertilizersPGPRsSemiochemicalsNano pesticidesGMOsSeaweeds
... The results are in line with Ford et al. (2007), Quinones et al. (2011). The sensitiveness of soil microbial biomass to land use practices like pesticide and fertilizer application and its contribution towards low soil microbial biomass carbon under vegetable and orchard farming systems and has also been reported by Hussain et al. (2009), Divya et al. (2012 and Ullah et al. (2013). ...
Impact of dominant land uses on soil quality in mid hills of North Western Himalayas was studied by undertaking an field experiment during 2015 and 2016 considering five land uses as treatments namely traditional agriculture, commercial vegetable, orchard,
forest and urban under randomized block design with four replications. Study indicated that dominant land uses has exerted significant impact on physical, chemical and biological properties of the soil. The soil under forest registered highest organic carbon (22.43 g kg-1), microbial biomass carbon (120.40 μg g-1) and WHC (40.61%) , whereas these were lowest under urban land use (15.33 g kg-1, 29.52 μg g-1 and 39.63%, respectively). The soils under commercial vegetable land use registered highest availability of N (381.36 kg ha-1), P (37.81 kg ha-1), K (199.24 kg ha-1), Cu (5.89 mg kg-1) and Fe (51.64 mg kg-1). Soil quality index calculated through PCA and was
observed that in the mid hills region soil was better under forest land use with index value of 0.78 followed by traditional agriculture (0.64), orchard (0.60), vegetable (0.60) and urban (0.59). The study indicated that urbanization, commercial fruit and vegetable
farming has deteriorated the soil quality NW of Himalayas.
... Table 1. Adsorption, desorption and mobility studies of different pesticides in soils that are indicator of biological equilibrium including soil fertility (Hussain et al. 2009;Mayanglambam et al. 2005), quality (Bucket and Dick 1998), and changes in the biological status of soil due to pollution (Nannipieri et al. 1990;Trasar-Cepeda et al. 2000). Degradation of both xenobiotic and natural substances in soil is catalyzed by this enzymatic pool (Floch et al. 2011;Kizilkaya et al. 2012). ...
... Multiple negative effects on AMF caused by pesticides, such as Benomyl, have been reported, including the inhibition of phosphorus uptake, enzymatic activity, and root colonization (Larsen et al., 1996;Kling and Jakobsen, 1997;Okiobe et al., 2022). In addition, non-target effects of pesticides like fungicides on nitrogen fixing bacteria have been documented, reducing nodulation and nitrogen uptake (Hussain et al., 2009;Getachew and Abeble, 2021). ...
Soil microorganisms play a key role in plant growth and health, and honey bees depend on plant pollen and nectar for their nutrition. Despite this clear above- and belowground connection, our knowledge about bee-plant-soil interactions is yet limited. Also, how these multitrophic interactions are affected by agricultural practices like pesticide applications is not well understood. Here we investigated possible non-target effects of soil application of the fungicide Benomyl on bee-plant-soil interactions in a greenhouse experiment with vetch (Vicia sativa L.). When plants were flowering honey bees were confined to their respective experimental soil treatments (untreated control, Benomyl and soil disinfection) in tents made from anti-insect mesh and micro-hives for foraging. At harvest, results showed that Benomyl and soil disinfection strongly affected key root and soil microorganisms essential for plant nutrition, such as mycorrhiza and rhizobia, and Gram-positive and Gram-negative bacteria, which coincided with phenotypic alterations in plant development and subsequently significant effects on honey bee nutrition and health, and finally honey production. In conclusion, our results show that soil application of the fungicide Benomyl strongly impact on bee-plant-soil multitrophic interactions, calling for further investigation on non-target effect of pesticides including multitrophic studies when evaluating environmental impacts of pesticides.
... Due to their widespread use during the 1990s, the herbicides Endosulfan and Atrazine were most frequently discovered in surface waterways in the USA and Australia. Diuron, Dimethoate, Profenophos and Fluometuron were among the other pesticides found [21]. In addition to damaging surface waterways and transporting pesticides to far-off locations, rainfall might also carry harmful chemicals. ...
Pesticides are chemical substances that are either produced chemically or naturally and are used to manage an extensive spectrum of pests. These chemicals are used in a variety of sectors, including forestry, agriculture, aquaculture, and the food industry. Pesticides show how hazardous they are to living beings. The World Health Organisation (WHO) classifies them depending on the damage that they do, emphasizing the significance of public health. It is possible to use them less harmfully for the environment and people's health by using them sparingly and with a good awareness of their classification. In this chapter, I have addressed how pesticides affect human health and the ecosystem, in addition to how they are used globally and in the context of India.
... To produce more crops from small landholdings and feed the large population, farmers especially in developing countries are applying agrochemicals in their farming practices (Gupta, 2012). Agrochemicals are the chemical compounds (fertilizer, pesticides, hormone, fungicides, insecticides, herbicides etc.) used in farming activities to protect the crops, fisheries and livestock from insects, pests and diseases which enhance the growth and development as well as quality and quantity of farm products (Omari, 2014;Hussain et al., 2009). However, considering the global scenario, there is no alternative to the use of agrochemicals in agricultural practices but the balanced use with optimum doses, and maintaining correct methods at right time has significant effects on farm production (Hurtig et al., 2003) but the requirements and efficiency of agrochemicals depend on the quality of products, application method used, soil health and meteorological characteristics (Gill and Garg, 2014a;Yáñ ez et al., 2002). ...
Agrochemicals are the part and parcel of modern farming practices. The study attempted to explore the effects of excessive use of agrochemicals oin farming practices. A structured questionnaire and face-to-face interview were conducted in collecting data from randomly selected 150 farmers of Satkhira sadar upazila under Satkhira district of Bangladesh during November 2022. The perceived effect of excessive use of agrochemicals was the focus variable whereas the selected socio-economic attributes of the participants were chosen as explanatory variables. The effect of overuse of agrochemicals was assessed employing a 4-point rating scale and ranked by calculating perceived effect index while the independent variables were measured using appropriate scoring techniques and scales. The findings revealed that, majority (48.7%) of the respondents perceived high positive effects of excessive use of agrochemicals on farming practices while a large portion (59.3%) of them perceived medium negative effects. It was also found that, the most positive effect perceived was increase productivity and cropping intensity (91.8%) while the worst effect was perceived as poisonous to human, animal, and soil microorganisms (82.7%). The results also explored that the main cause of overuse of agrochemical is provision of higher yield (94.7%) whereas the best management practice suggested by the farmers was agricultural training (95.3%). However, perceived effect of agrochemical usage was found positively correlated with respondents’ educational qualification, farming experience, agricultural training, extension media contact, knowledge, and awareness. So, appropriate strategies along with sustainable farming system is crucial to protect our environment and save our upcoming generations.
... Thus the injudicious and indiscriminate use of pesticides has resulted in tremendous loss to environment and human health. Furthermore, pesticides have also been reported to adversely affect the microorganisms in soil responsible for nitrification 27 . Along with the target, pesticides also affect beneficial soil microorganisms, natural enemies to insect pests, fish, birds and other wildlife, thus adversely affecting the tritrophic interactions, food chains and food webs directly and indirectly. ...
Home gardens are widely regarded as the model for sustainable agroforestry systems. The most intricate artificial combination of trees, crops, and animals provides essential ecosystem services while closely approximating a natural ecosystem. High biodiversity, helpful nutrient cycling, minimal reliance on outside resources, and the opportunity for soil conservation are also present. The home
garden has great potential for in situ conservation of heritable income and economic worth of the produce grown. The economic benefits are the advantages beyond ensuring food and nutritional security and sustenance. The environmental benefits are the complexity of home gardens that can make them resemble ecological agricultural production systems that support biodiversity preservation. Function and structure are inextricably intertwined. Persistent pressure for change is brought on by demographic, economic, technical, and social factors. Home gardens are adapting to changing livelihoods. Maintenance of biodiversity and carbon sequestration is the complementary environmental service of any ecological unit, including agroforestry. Women's role in home gardens depends on several factors, including their careers. The secret to transforming home gardens into sustainable businesses is to make them productive and long-lasting. Home gardens are not an
exception; changes in the local ecology, economics, and culture will undoubtedly have an impact on them.
... Herbicides are involved in soil processes like retention, transformation and transport. These herbicides may influence more or less the biological activity of soil, which is the result of microbial and enzymatic transformations (Engelen et al., 1998;Hussain et al., 2009). The inhibition of soil enzymes by agrochemicals can be direct or indirect. ...
A pot culture experiment was conducted to investigate the effect of a few pre-emergence herbicides on soil L-glutaminase activity (µg of NH 4 + released g-1 soil 4h-1) in a Vertisol and in an Alfisol. The experiment was under taken with pre-emergence herbicides viz., pendimethalin 30% EC (1 kg a.i/ha) for groundnut, greengram, sunflower and bhendi, atrazine 50% WP (1 kg a.i/ha) for maize and bensulfuron methyl 0.6% + pretilachlor 6% GR (0.66 kg a.i/ha) for rice. The experiment was conducted in a completely randomized block design with three replications. The results shown that in pendimethalin treated Alfisol and Vertisols L-glutaminase activity slowly increased from 0 days after application (DAA) to 30 DAA but later significantly increased upto 60 DAA in all treatments. Activity of L-glutaminase in the pendimethalin treated pots is lower than control upto 45 DAA in Alfisol and 30 DAA in Vertisol. Similar type of pattern was observed in atrazine treated maize crop. But in case of Bensulfuron + Pretilachlor treated Alfisol and Vertisol pot cultures, soil L-glutaminase activity decreases from 0 to 15 DAA but later activity of enzyme significantly increased from 15 to 60 DAA. Activity of L-glutaminase in the herbicide treated pots is lower than control up to 15 DAA in both Alfisol and Vertisol pot cultures.
... As part of maintaining soil fertility and productivity, soil microbes degrade organic matter, recycle nutrients, form humus, stabilize soil structurally, fix nitrogen, promote plant growth, and control disease through biochemical transformations such as ammonification, nitrification, phosphorus solubilization [5]. It has been demonstrated that pesticide use in arable farming contributes to soil and environmental contamination [6]. ...
Agricultural production is largely based on the use of agrochemicals in order to minimize pests, pathogens, and undesirable weeds toward increase production. In the current situation, however, several threats are emerging that threaten food security, human and environmental health, ecological balance, and soil biodiversity. Agrochemicals may shift beneficial microorganisms in the community over time, with potentially dangerous consequences, such as the development of antibiotic resistance. Farming systems utilizing agrochemicals might adversely affect soil microorganisms responsible for nutrient cycling processes, such as: nitrogen fixation, phosphorus solubilizing, and others. Some agrochemicals reduce soil enzyme activity and biochemical reactions, which are key indicators of soil microbiology. In this review, we explore how applied agrochemicals affect soil microbes and biochemical health attributes under different cropping systems, as well as ways to overcome the negative impacts of agrochemicals.
... In Bangladesh, pesticide misuse has become more common, posing a significant threat to soil ecology. The intensive use harms soil health as pesticide toxicity destroys soil microorganisms, and long-term application disrupts biochemical equilibrium, disrupts nitrogen fixation, and inhibits the activity of soil enzymes (Hussain et al., 2009). The plate count data revealed the adverse impact of respective pesticides on fungi, heterotrophic bacteria, and nitrogen transportation bacteria (Cycon and Piotrowska-Seget, 2007). ...
The recent trend of Pesticide use is accelerating for agricultural production purposes. Its importance is immense for controlling pests in developing countries like Bangladesh. But the imprudent application is increasing at an alarming rate due to which environmental degradation is increasing, which is not still under investigation. Despite the various pest control methods, chemical pesticides (hereafter pesticides) are more popular among Bangladeshi farmers because of their low cost and rapid action. The continuous popularity of pesticides application adversely affects the environment, and eventually, human throughout the country. Hence a systematic review was initiated utilizing the secondary information to overview the hazardous impact or prevailed pollution due to the application of pesticides in the context of the environment, related organisms, and human health. The analysis revealed that pollution-related problem arises mostly due to the unregulated use of pesticides. Therefore, excessive pesticide usage such as pollutes the air, soil, and water and kills non-target organisms, causing an ecological imbalance. Lack of protection exposes farmers to acute illnesses, toxic compounds in the food cycle, and the mass population to chronic health issues. Thus, to minimize pesticides' environmental, and health effects, concerns should be given on the judicious application of pesticides, raising awareness regarding pesticide use. Policymakers should focus on raising awareness regarding the use of pesticides, implementing effective pesticide usage laws at the root level, optimizing reasonable use, participatory program implementation for farmers' training, good governance and regulatory mechanisms, frequent inspection at the field level, and appropriate actions and strategies for promoting eco-friendly methods.
This study investigates the effects of dichlorvos, dimethoate, and cypermethrin, individually and in combinations, on maize (Zea mays) growth and physiology. Maize seeds were grown in pesticide-treated soil, and growth parameters, oxidative stress markers, and enzymatic activities were evaluated. Growth was significantly inhibited by pesticide exposure, with Group H (triple pesticide combination) showing the most severe reduction in plant height (48% lower) and stem girth (40% lower) compared to the control (p < 0.05). Biochemical assays revealed significant declines in catalase (CAT) and superoxide dismutase (SOD) activities across all tissues, indicating compromised oxidative stress defenses. For instance, CAT activity in roots decreased by 65% in Group H compared to the control (p < 0.05). Concurrently, malondialdehyde (MDA) concentrations, a marker of lipid peroxidation, increased significantly, with Group H showing a 75% rise in leaves relative to the control (p < 0.05). Relative water content (RWC) also decreased substantially, with Group H recording the lowest hydration levels (37% reduction, p < 0.05). These findings suggest synergistic or cumulative toxicity from combined pesticide exposure, with the most pronounced effects observed in triple pesticide treatments. Statistical analyses (ANOVA, Tukey's test) confirmed significant differences across groups (p < 0.05), reinforcing the reliability of the results. This study highlights the adverse impacts of pesticide combinations on maize growth and physiological stability, emphasizing the need for sustainable pest management strategies, such as integrated pest management (IPM), to mitigate the ecological and agricultural risks of pesticide use.
The heterotrophic and haloxyfop-R methyl ester utilizing fungal counts associated with two top soil samples was determined. Five (5) fungal isolates; Aspergillus niger, Candida sp., Trichoderma sp., Fusarium sp., and Alternaria sp. Were cultured from the soil samples using serial dilution as well as pour plate techniques. These isolates were sub-cultured and screened for their ability to use haloxyfop-R methyl ester as sole source of metabolic energy as well as using the turbidimeteric method. Two of the screened fungal isolates which exhibited maximal optical density (OD) difference values; A. niger and Fusarium sp. Were selected and utilized for the subsequent degradation/shake flask experiment. Growth profile parameters which included; pH, OD, dissolved CO2 and weighed dry fungal biomass were determined during the growth profiling test at a 96 hour interval for 16 days using appropriate methods and equipment. Mean soil pH values were 5.08 ± 0.02 and 4.62 ± 0.02 for samples A and B. The mean total heterotrophic fungal count was 8.7×10³ cfu/g ± 1.5 for A and 1.6 × 10⁴ cfu/g ±1.0 for B. The mean pH value observed for A. niger in the course of the growth profile test ranged from 6.0 ± 8.7 to 7.3 ± 8.0 and 7.3 ± 5.8. The mean OD values observed for A. niger and Fusarium sp. In the course of the shake flask experiment varied from 0.66 ± 7.1 to 1.96 ± 4.5 and 1.62 ± 5.4 to1.99 ± 3.6 respectively. With reference to the detection of mean dissolved CO2 values, utilized as an indirect indicator of herbicide mineralization, the axenic cultured A. niger was the most effective amongst the growth profile fungal cultures.
Pesticides are one of the largest groups of environmental pollutants used to protect agricultural plants from different pests and weeds. Soil is the initial area of accumulation of pesticides after their release into the environment. Determination of pesticides in soil is complicated by matrix effects and laborious sample preparation which generally involves the use of large amounts of organic solvents. Development of accurate green analytical methods for determination of pesticides in soil is an urgent task in environmental and analytical chemistry. In this study a method based on vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) coupled with gas chromatography-mass-spectrometry (GC-MS) was developed for the quantification of nitrogen-containing pesticides in soil samples. The pesticides atraton, simazine, atrazine, propazine, diazinon, metribuzin, prometryn, and oxyfluorfen were target analytes. The effects of water addition, reduced pressure, salting-out and pH adjustment on the extraction efficiency of target pesticides from soil were studied. Using Vac-HSSPME, the increase in the responses for all target pesticides by 3-7 times compared to ambient-pressure HSSPME was observed. Addition of water resulted in 2 to 380 times increase of the peak areas of analytes obtained using Vac-HSSPME. Optimum Vac-HSSPME performance was achieved using 60 min extraction at 60 °C. The proposed method can be recommended for quantification of atraton, atrazine, propazine, diazinon, prometryn, and oxyfluorfen in soil. Under optimum conditions the weighted linear regressions with R 2 > 0.949 were obtained for most analytes in the concentration range 25-200 ng/g. The limits of detection and quantification ranged from 0.1 to 4 ng/g, and from 0.4 to 12 ng/g, respectively.
Many plant and animal species have undergone extensive domestication as a result of ongoing agricultural intensification and extensive human sociocultural and economic development in a bid to improve global food production and security. However, the rise in consumption rate brought on by global population growth presents a constant and growing challenge. Therefore, many scientific and cutting-edge avenues are being explored to increase agricultural output and assured food security for everyone, especially in developing and underdeveloped parts of the world. These include the use of chemicals such as a broad class of pesticides - herbicides for weed and insect pest control as well as for greater yields and fertiliser applications for better crops and animal production. However, as the usage of these chemicals increased, so did their detrimental effects on soil microorganisms, above-ground flora, and other connected natural resources, and the quality of environmental matrices like soil, water, and air pollution. The types and classifications of agrochemicals, especially herbicides and fertilisers used in developing and underdeveloped countries exacerbate the effects, and impacts on soil microbes and vegetation. This chapter focuses on the issues related to the current realities of chemical application for agricultural productivity on above-ground flora and soil microorganisms and discusses potential sustainable management approaches.KeywordsHerbicidesFertilisersAgricultureVegetationSoil microorganismsFood securityPollution
Clay minerals have gained a huge attention of the researcher in recent years owing to their widespread applications in environment, agriculture, industry, and pharmacy. Despite of the unique properties of clay, there are some limitations in agricultural and environmental applications of clays, which includes removing hydrophobic organic micropollutants, utilization of fixed-bed media and in flocculation water treatment. Therefore, several researchers have attempted to fabricate clay-based composites with other materials such as biochar to improve and tune the properties of clays for targeted applications. Biochar is produced from the pyrolysis of waste materials and is characterized by a negative surface charge, larger surface area, numerous surface functional groups, high cationic exchange capacity, higher recalcitrance, and large pore volume. Therefore, synthesis of clay–biochar composites via surface, chemical, mechanical, or physical modifications could generate efficient materials with improved characteristics for specific applications. Thus, the techniques to synthesize clay–biochar composites for various applications are reviewed and discussed in this chapter. The variations in the chemical, physical, surface, and structural characteristics of clay–biochar composites are also discussed. Moreover, efficient, cost-effective, and environment-friendly technologies to synthesize clay–biochar composites are highlighted, and new emerging applications are recommended.KeywordsEngineered materialsIntercalationEnvironmental pollutionSurface modificationsRemediation
The accumulation of various contaminants in water has become a threatening environmental issue, affecting all living creatures. Owing to this fact, mitigating water contamination problems by improving existing technologies and developing potential strategies has become an emerging area of research. Among several approaches for water treatment, adsorption has been attractive since it has unique advantages due to the use of natural and synthetic materials. As a natural adsorbent material, clay minerals are considered superior materials owing to their wide availability, low cost, excellent adsorption performance and cation exchangeability. To enhance the surface properties toward the removal of water pollutants, natural clays are subjected to various modifications. The surfactant-modified clay composites can remove a variety of pollutants than other composites due to the sorption of surfactant onto the external surface and interlayer spacing of clay minerals. This chapter encloses the application of surfactant-modified clay towards the removal of pollutants from water.KeywordsClay compositeSurfactantAdsorptionIon exchangeWater treatment
Con el objetivo de realizar una reflexión sobre las posibles consecuencias por el uso de plaguicidas por los agricultores de Puerto La Boca, se implementó una investigación, se preparó una encuesta con 35 preguntas cerradas que fueron aplicados a 155 personas (31 familias). El experimento fue implementado en un diseño experimental completamente aleatorio en arreglo factorial con 2 factores, factor A: plaguicida y/o productos orgánicos y factor B: Dosis. Los resultados expresaron que los ingredientes activos para los fungicidas líquidos más usados fueron el Cymoxanil + Clorotalonil, para el control de los Oomycetes como Pseudoperonospora cubensis, y Phytophthora infestans causantes de los mildius en Cucurbitáceas y Solanáceas respectivamente. Los insecticidas como el Imidacloprid y Methomyl, fueron los más utilizados para controlar el pulgón (Myzus persicae), lorito verde (Empoasca sp.), minador de hojas (Liriomyza trifolii), trips (Trips tabaci) y negrita (Prodiplosis longifilia). Los microorganismos más utilizados fueron Trichoderma sp. y Bacillus thuringiensis, para el control de insectos-plaga como la polilla (Diaphania sp.) y las enfermedades como Fusarium sp. y Rhizoctonia solani, en cultivos de melón, sandía, pepino, cebolla, pimiento y tomate. Se determinó que los agricultores de Puerto La Boca sub-dosifican y/o sobre-dosifican los fungicidas e insecticidas sólidos y líquidos en las aplicaciones que realizan. Lo agricultores necesitan fortalecer sus conocimientos sobre el uso y manejo de los plaguicidas.
The world population is increasing by 81 million every year and people need more agricultural production to avoid hunger. Despite modern farming methods, where advanced technologies and new production systems such as soilless agriculture are applied, production seems far from meeting the nutritional needs of people today or in the future. Although phytopathogens, insects and weeds, which cause significant yield and quality losses in agricultural products, are struggled today, it is estimated that the total loss of crops is 36.5% in the world every year due to these pests. Plant protection practices (cultural measures, physical control, legal measures, biological control, chemical control, alternative control) are carried out against pests in order to prevent product yield and quality losses in agriculture. Among these applications, chemical control is the most effective control method against pests, the results of which can be seen in a short time. However, especially in conventional agriculture, irregular and intensive pesticide applications made to protect yield and quality with economic concerns cause environmental pollution and deterioration in soil, water resources and troposphere ecosystems. In this review, the effects of plant protection practices on non-target organisms in different ecosystems are presented.
A pot experiment was conducted to study the effects of insecticides on soil micro-biota
under laboratory condition. Soil was collected from control plot (0-15 cm depth) where no
insecticides were applied and filled in plastic pots. Three insecticides viz. indoxacarb 14.5
SC, chlorfenapyr 10SC and chlorpyrifos 20EC with two doses were applied twice at 15 days
of interval on the pot soil surface. Sampling of soil from pot was done by using PVC core (1
inch diameter) after 72 hours of each spray. Inoculation of serially diluted soil solution was
done on culture media for microbial count. The number of colonies of bacteria and fungi on
the plates were counted directly or with the help of a colony counter. The results revealed
that the higher mean log CFU/g population of soil bacteria was recorded in the normal dose
indoxacarb (5.77-5.99 cfu/g of soil) and chlorfenapyr (5.79-5.83cfu/g of soil) whereas soil
fungi was higher in normal dose of indoxacarb (5.49-6.10 cfu/g of soil) and chlorpyrifos
(5.54-5.99 cfu/g of soil).
Pesticides (PS) are a significant tool for controlling plant pathogens, pests, and weeds, which is important for crop economic yield. Pesticides are divided into two types: natural compounds and synthetic compounds. In addition, to use in agriculture, pesticides are used in a variety of fields, including industry and medicine. In agriculture, pesticides are used through harvest and post-harvest in grains, vegetables, and fruits. Fruits are an important crop for human consumption. Pesticides and chemicals used in food preservatives are formed from one or a group of chemicals. Nearly all chemicals used as PS or food preservatives have toxic effects, but this depends on the type of chemical and its concentration, including organic acid, chelating agents, antioxidants and antimicrobial agents. The increase and continued use of pesticides and food preservative shave led to concerns about food safety and crop productivity. One particular cause for concern about these two materials is that residues of synthetic chemicals that may be particularly toxic to humans have been detected in food. The toxic effects of synthetic chemical preservatives on human health include allergies, heart palpitations, headaches, and cancer. It may be possible to use natural compounds infoodandfruit, safer preservation and not pose risks to human or environmental health. Natural compounds can be derived from plants or useful microorganisms. Therefore, natural compounds are considered preferable to synthetic compounds for fruit preservation.
A laboratory experiment was conducted to study the effect of selected fungicides, tridemorph and
captan, at concentrations ranging from 0 to10 kg ha-1 on the activity of invertase and cellulase in a
vertisol. The activities of invertase and cellulase were significantly more at tridemorph and captan
levels of 2.5 and 5.0 kg ha-1, respectively. But at higher concentrations of 7.5 and 10 kg ha-1respectively,
tridemorph and captan were toxic to both cellulase and invertase activities. In soil samples receiving
2.5-5.0 kg ha-1 of the fungcides, the accumulation of reducing sugar was pronounced more at 20 days,
and the activity of the invertase and cellulase was drastically decreased with increasing period of
incubation up to 30 and 40 days.
The factors influencing pesticide biodegradation in soils are described: structure, concentration and treatment history of the pesticide; soil properties (moisture, temperature, organic matter, clay content, pH, redox, structure), and the number, specific activity, and metabolism of the microorganisms. Microbial pesticide transformation reactions are reviewed: oxidative reactions (hydroxylation reactions, dealkylation reactions, epoxidation, sulfoxidation), reduction reactions, hydrolytic reactions, and synthetic reactions and the formation of immobilized residues. The metabolism and cometabolism of pesticides and adaptation and the development of new degradative capabilities are discussed. The prediction of pesticide fate in soils and applications of pesticide-degrading bacteria, enzymes, and genes are described. Inhibitory effects of pesticides on soil microorganisms are discussed.
Pesticides (Brominal, Cuprosan and Fenvalerate) at 10 and 50 ppm suppressed growth, respiration and nitrogenase activity ofAzotobacter chroococcum, Azospirillum brasilense andAzospirillum lipoferum. The inhibitory effect on respiration ofAsm. lipoferum was most pronounced after 3 and 4 days.
Summary This investigation studied the effects of trichlorfon on the growth and some physiological activities of the common freshwater alga Scenedesmus bijuga in the River Nile. The results showed that the cell number and Chl. a content of Scenedesmus bijuga decreased with increase in trichlorfon concentration. The data also showed that the total carbohydrate contents of Scenedesmus bijuga increased following treatment with low concentrations of trichlorfon (0.1 mM). All the applied treatments of trichlorfon strongly reduced the total protein content of Scenedesmus bijuga in comparison to control values. A gradual increase in total amino acids content was generally a function of trichlorfon concentration increase from 0.1to 0.4 mM. As regards to nucleic acids the maximum level (0.58 and 1.60 mg g -1 DW of DNA and RNA, respectively) was obtained at 0.1 mM concentration of trichlorfon. However, any increase above this latter level was inhibitory. Trichlorfon treatment suppressed the activity of both acid and alkaline phosphatase in Scenedesmus bijuga. Consistently with this response, higher doses of the insecticides (0.4 and 0.8 mM) increased the glutamic oxaloacetic transaminase (GOT) and glutamic pyruvate transaminase (GPT).
This study measured the spatial dependence of soil enzyme activities and other properties of the Ap horizon in a Gray Brown Luvisol (Hapludalf). Soil samples were collected at 74 positions along a slope following harvest of soybean [Glycine max (L.) Merr.] and fall tillage. Parameters measured were activity of dehydrogenase, urease, glutaminase, phosphatase, arylsulfatase, and β-glucosidase; water, organic carbon (OC), mineral N, and inorganic P contents; the light fraction of soil organic matter; and depth of the Ap horizon. Rank correlation indicated significant relationships between water and dehydrogenase, urease, glutaminase, phosphatase, and arylsulfatase activities, and between water and OC content. Depth of the Ap horizon, water content, and arylsulfatase activity were strongly spatially dependent; OC and inorganic P contents and phosphatase activity were moderately spatially dependent. Other properties showed little or no spatial dependence. The ranges of spatial dependence were similar for depth of the Ap horizon, inorganic P content, and phosphatase activity (≃20 m). The range for arylsulfatase activity was 16 m, while that of OC content was 32 m. The relatively long range estimate for water content (98 m) was influenced by a trend along the slope. Maps of water and OC contents and phosphatase and arylsulfatase activities indicated similar spatial patterns along the slope. The magnitude of these soil properties was minimal in the middle or upper portion of the slope, and maximal at the footslope. Similarity in spatial patterns along the slope was interpreted as evidence for influence of water or OC content on amounts of phosphatase and arylsulfatase at that scale.
Effects of metsulfuron-methyl on the activities of amylase, urease, and protease in loamy sand (Sungai Buluh series) and clay loam soil (Lating series) were evaluated for up to 28 days. Metsulfuron-methyl at 5· 0 µg/g caused a reduction in amylase and urease activities for the entire period of study, especially at 28 days of incubation. A similar trend was observed in Lating series soil where the lowest activities of amylase and urease were attained at Day 28 in the presence of 5 ·0 µg/g of metsulfuron-methyl. The protease activity in either Sungai Buluh or Lating series soil decreased during the 7 days of incubation compared with that of the control, but a recovery trend was obvious at all concentrations from Day 14 onwards.
Temporal fluctuations in rates of nitrogen mineralization and the activities of six enzymes were measured in topsoil, predominantly a Typic Haplaquoll, from two plots that contained pastures of different age in the Wairarapa area. Samples were taken at c. 4-weekly intervals for over one year. Organic carbon contents averaged 6.7 and 3.6% in soil from the older and younger pastures respectively. Net mineral-nitrogen production at 25°C was higher in soil at a standardized water potential (-3 and -4 kPa for soil from the older and younger pastures respectively) than at field moisture content. It was initially higher in soil from the younger than from the older pasture. Generally, distinct seasonal patterns were not apparent. All of the enzyme activities showed significant temporal fluctuations. Amylase and cellulase activities fluctuated more than invertase activity, but all three carbohydrase activities were generally high in wet spring samples. When plot effects were removed, only the fluctuations in amylase activity were related positively and significantly to soil moisture content. Fluctuations in cellulase, urease, phosphatase and sulphatase activities were correlated negatively with soil moisture content. The temporal fluctuations in enzyme activities were, when plot effects were removed, mainly independent of the small variations that occurred in soil organic carbon and total nitrogen contents. Interrelationships of these biochemical properties, and relationships with rates of CO2 production and indices of microbial biomass, are discussed.
Till now the effects of fungicides with the active ingredients anilazin and dichlofluanide on soil microorganisms were only scarcely investigated. Therefore. we applied two fungicides with these active ingredients in comparison with the herbicide 'Flussig Herbogil' (dinoterb) used as reference compound under laboratory conditions to two agricultural soils. Like the herbicide both fungicides mostly inhibited biomass-related activities (dehydrogenase, substrate-induced respiration = KZA) dose-related and stimulated the nitrogen mineralization (= Nmin). The carbon mineralization (cumulative long-term respiration = LZA) was only sometimes increased. The quotient of LZA and KZA responded as a sensitive stress indicator with an increase, whereas the quotient of LZA and Nmin was decreased. Most effects lasted over the whole trial period of 12 weeks, but they depended on soil type and often were modified by organic amendments (lucerne meal).
Monocrotophos, quinalphos, cypermethrin and fenvalerate, at concentrations ranging from 0 to 10 kg ha-1, were tested for their nontarget effects towards activity of phosphatases in four vertisols. In soil samples receiving 2.5 kg ha-1 of the insecticides, the activity of phosphatases was significantly more at 20 days and decreased progressively with increasing period of incubation.
Addition of compost from various sources and of different maturity may affect the soil biochemical properties. A field study was conducted to evaluate the effect of different composts, spring-applied alone or in combination with ammonium nitrate (AN), on microbial biomass C (MBC) and alkaline phosphatase activity (APA) in two soils cropped with spring wheat (Triticum aestivum L. 'Messier') in eastern Quebec, Canada. The experiment was conducted in 1994 and 1995 at different sites on a Kamouraska clay (Orthic Humic Gleysol) and a Saint-Andre sandy loam (Fragic Humo-Ferric Podzol). Treatments included composts at 180 kg N ha-1, composts at 90 kg N ha-1 supplemented with AN, AN at 90 kg N ha-1, and an unfertilized control. Soil MBC and APA were measured 30 d after compost application and at wheat harvest. Additional sampling was made the following spring. Generally, larger MBC and APA values were found at wheat harvest in soils treated with composts alone than with AN alone or unfertilized. These effects were related to soil C content and climatic conditions. Compost type affected soil biochemical properties which could be attributed to the total C supply and material maturation state. Compost addition constitutes an efficient short-term way to promote soil microbial biomass and enzyme activity in cold climates.
Methane oxidation by soils is an important sink for this greenhouse gas. When tested at 50 mg L−1, the herbicide bromoxynil, the insecticide methomyl, and the nitrification inhibitor nitrapyrin inhibited methane oxidation by soil slurries. The results suggest that these chemicals might decrease methane oxidation by agricultural soils. Key words: Soil methane oxidation, inhibition, agrochemicals
Field experiments were conducted in northern Thailand to evaluate the effect of five herbicides and three watering schedules on soybean yields and N2 fixation. The herbicides sethoxydim, alachlor, fluazifop butyl and metolachlor when added at recommended rates for weed control did not result in detrimental effects on seed yields or benefits of N2 fixation. Paraquat additions significantly reduced the amount of N2 fixed as measured by15N dilution methods. Inoculation of the soil with a mixed strain inoculum of Bradyrhizobium japonicum increased seed yields and measurements of N2 fixation. The application of water to soybeans only when water stress symptoms such as wilting were observed resulted in drastic reductions in both yield and N2 fixation of four cultivars of soybeans. Reducing the water application from weekly to biweekly did not seriously reduce yields or N2 fixation benefits.
An experiment was conducted to investigate the effect of four non-conventional organic wastes viz., Justicea simplex, Jatropa gossypifolia, Ipomoea cornea and Cestrum diurnum at a concentration of 0.5% (on soil weight basis) on the rate of decomposition and the microbial dynamics in soil. Justicea simplex liberated the maximum amount of carbon dioxide from soil on the 2nd day. Other organic additives liberated the highest amount of carbon dioxide on the 3rd day. During 84 days of decomposition, the cumulative amount of CO2 evolution was in the order: Justicea simplex > Cestrum diurnum > Ipomoea cornea > Jatropa gossypifolia. Different organic residues exerted differential stimulation of microbial proliferation in the soil. Jatropa gossypifolia gave rise to the maximum number of total bacteria in soil. Cestrum diurnum and Jatropa gossypifolia induced a similar effect on the actinomycete population. The augmentation of fungal colonies in the presence of different wastes was similar. Cestrum diurnum harboured the maximum number of non-symbiotic nitrogen-fixing bacteria and phosphate-solubilizing microorganisms. Justicea simplex and Jatropa gossypifolia were superior to Cestrum diurnum and Ipomoea cornea with respect to nitrogen fixation. None of the organic additives stimulated the phosphate-solubilizing capacity of the soil.
Among the four insecticides under study, hexachlorocyclohexane (BHC) followed by phorate signi®cantly stimulated the populations of (total) bacteria, actinomycetes, fungi, aerobic non-symbiotic N 2-®xing bacteria and P-solubilizing microorganisms in soil. Carbofuran signi®cantly stimulated total as well as N 2-®xing bacteria. Fenvalerate had no effect on P-solubilizers. All the insecticides stimulated the proportion of Penicillium in soil. Similarly, Pseudomonas with BHC, Sarcina with phorate, Corynebacterium, Azotobacter and Streptomyces with fenvalerate were also stimulated. On the other hand, Erysipelothrix with BHC, Staphylococcus with phorate, Staphylococcus, Nocardia and Fusarium with fenvalerate were inhibited. Almost all the insecticides reduced the proportions of Micrococcus and Rhizopus in soil. Insecticides also augmented the non-symbiotic N 2-®xing and P-solubilizing capacities of the soil and the augmentation was more pronounced with BHC followed by phorate.
An experiment was conducted under laboratory conditions to investigate the effect of four insecticides, viz. HCH, phorate, carbofuran and fenvalerate at their field application rates (7.5, 1.5, 1.0 and 0.35 kg a.i. ha −1 , respectively), on the growth and development of bacteria, actinomycetes and fungi as well as their role in the transformations and availability of some plant nutrients in laterite soil (Typic Orchragualf). All the insecticides in general, and HCH and phorate in particular, significantly increased the population of microorganisms in soil. The most predominant genera of microorganisms, such as Bacillus, Micrococcus and Aspergillus were not affected by most of the insecticides. However, some of the insecticides stimulated the growth and development of Bacillus, Proteus, Corynebacterium, Streptomyces, Fusarium, Trichoderma and Rhizopus. On the other hand, some insecticide exerted deleterious effect on the proportions of Pseudomonas, Staphylococcus, Nocardia, Micromonospora, Aspergillus and Rhizopus. Incorporation of insecticides also significantly stimulated the mineralization and availability of organic C, N and P in soil. Among the tested substances, the stimulations were more pronounced with HCH followed by phorate and fenvalerate.
Four insecticides, viz., BHC, phorate, carbofuran, and fenvalerate, were applied at the rate of 7.5, 1.5, 1.0, and 0.35 kg a.i. ha(-)(1), respectively, to investigate their effects on the growth and activities of N(2)-fixing and phosphate-solubilizing microorganisms in relation to the availability of N and P in laterite (Typic Orchragualf) soil. Insecticides in general, and BHC and phorate in particular, stimulated the proliferation of aerobic nonsymbiotic N(2)-fixing bacteria and phosphate-solubilizing microorganisms and also their biochemical activities, such as nonsymbiotic N(2)-fixing and phosphate-solubilizing capacities, which resulted in greater release of available N (NH(4)(+) and NO(3)(-)) and P in soil. All the insecticides were persistent in soil for a short period of time, and the rate of dissipation was highest for fenvalerate followed by phorate, carbofuran, and BHC, depicting the half-lives (T(1/2)) 8.8, 9.7, 16.9, and 20.6 days, respectively. The insecticides followed first-order reaction kinetics during their dissipation in soil.
After enumerating the groups of soil enzymes, their activity as potential biological/biochemical indicators is discussed, firstly with reference to the ecology and function of soil enyznmes and their activity in relation to soil microbial activities. Next, soil enzyme activities as indicators of perturbation are considered, particularly the long-term effects of soil management, temporal responsiveness of soil enzymes, and approaches to a biological index of soil fertility. The use of soil enzyme assays in research is reviewed, and conclusions are made on the potential for measuring enzyme activity as an indicator of soil quality. -J.W.Cooper
Methamidophos in an equivalent concentration of either 0.5 or 2.0 ppm was thoroughly mixed with soil 1 (loamy sand), soil 2 (clay) and soil 3 (clay loam). Experiments using soils 1 and 2 were carried out in the greenhouse, and the soil 3 investigation was carried out under field conditions. The cellulosic materials were either buried 4 cm or placed on the soil surface. In soil 1, 2 ppm methamidophos reduced the decomposition of cellulosic material by 41 and 55% of the untreated control, at the soil surface or buried in soil, respectively, at 12 weeks incubation. In soils 2 and 3, methamidophos at 2 ppm did not reduce the mass loss of the substrates either placed on the soil surface or buried in the soil. The carboxymethyl cellulase (CMCase) activity extracted from the substrates on soil 1 treated with 2 ppm methamidophos was reduced by 37.5 and 16% of the untreated control, at 6 or 12 weeks, respectively. The activity was not affected in soil 2, when the substrates were placed either on the soil surface or buried 4 cm. In soil 3, CMCase activity of the substrate was reduced by 25% when the substrates were placed on the soil surface at 6 weeks incubation. Other treatments did not affect CMCase activity significantly.
A coring technique was used to intensively sample the litter layer of a red maple (Acer rubrum) woodlot in the vicinity of Ottawa, Canada. Monthly changes in the litter standing crop provided an accurate estimate of the decomposition rate of red maple litter during 2 summers and 1 winter both under natural conditions and when treated with the insecticide Carbofuran@R. The Standing crop of litter ranged annually between @?275 and 700 g/m^2 and decomposed at a rate between 1.48 and 2.19 g@?m^(-2)@?day^(-1) under natural conditions between May and November. A common carbamate insecticide (Carbofuran@R) applied at recommended rates reduced the decomposition rates to between 0.99 and 1.26 g@?m^(-2)@?day^(-1) resulting in an increase in standing crop.
We compared decomposition of surface and buried, untreated, mixed desert shrub litter to that of insecticide- and fungicide-treated litter. Suppression of fungi reduced decomposition by @?29%; exclusion of microarthropods reduced decomposition by @?53%. Approximately 55% of the organic mass of the untreated litter disappeared during the 6-mo growing season and 23-29% disappeared in the winter months (November through March). There was a consistent pattern of microarthropod colonization of buried litter that was related to the percent organic matter lost. This sequence was tydeid mites, tarsonemid and pyemotid mites, gamasina and predatory Prostigmata, Collembola and Psocoptera, and oribatids. After 1 yr, large numbers of enchytraeid worms were extracted from buried litter. Decomposition of insecticide-treated litter varied directly with rainfall and soil temperature while abiotic factors accounted for <50% of the variation in decomposition of untreated buried litter. We hypothesize that microarthropods affect litter decomposition in deser ecosystems by inoculating litter with fungal spores, by grazing on fungi, and in a heretofore underscribed mode, by preying on free-living nematodes.
Laboratory tests were conducted with eight herbicides, atrazine, butylate, ethalfluralin, imazethapyr, linuron, metolachlor, metribuzin and trifluralin, applied to a loamy sand at rate of 10 μg/g to determine if these materials caused any serious effects on microbial and enzymatic activities related to soil fertility. Some herbicides showed an effect on bacteria and fungi for the first week of incubation, but, subsequently, the populations returned to levels similar to those obtained in the controls. After several herbicide treatments there appeared to cause a slight depression of nitrification. Sulfur oxidation was better than that obtained with untreated soil in all treatments. Oxygen consumption was increased significantly after 96 hr incubation with atrazine. The soil dehydrogenase and amylase activities were inhibited by ethalfluralin treatment respectively for 1 wk and 1 day, and p‐nitrophenol liberation was inhibited for 2 hrs by all herbicide treatments. Results indicated that the herbicidal treatments at the level tested were not drastic enough to be considered deleterious to soil microbial and enzymatic activities which are important to soil fertility.
A soil sample from the Ap horizon of an arable brown soil was fractionated by wet sieving, and seven size fractions of organic and mineral soil particles were separated. The organic fractions formed only 2.2% of the soil dry mass, but contained 41.5 and 29.12% of the total soil content of carbon and nitrogen, respectively, and thus represented an important reservoir of readily utilizable nutrients. Organic particles also accumulated most of the soil enzyme activities, determined asβ-glucosidase,β-acetylglucosaminidase, and proteinase activity. The highest counts of bacteria, actinomycetes, and fungi per gram of the soil fractions were obtained with the organic particles, but for the most part microorganisms accumulated in the silt-clay fraction. All soil fractions except the coarsest organic particles contained higher counts of oligotrophic bacteria than copiotrophic ones. Microbial counts, ATP contents, and enzyme activities decreased significantly with decrease in size of the organic soil particles, and increased with decrease in size of the mineral soil particles. Thus, the coarse organic particles >5 mm and the silt-clay fraction <0.05 mm represent the sites with the highest concentrations of microorganisms, ATP contents, and enzyme activities in the arable brown soil under test.
A study was made of the effects of insecticide profenofos at concentrations of 10, 50, 100, 200 and 300 μg per gram of soil on total bacteria populations, fungi, dinitrogen fixer, denitrifying bacteria, nitrifying bacteria (phase I and II) and nitrogenase activity (C2H2 reduction) in an agricultural soil. The presence of 10 to 300 μg/g significantly increased the total number of bacteria and denitrifying bacteria. However, the population of aerobia dinitrogen fixing bacteria and dinitrogen fixation were suppressed significantly. Nitrifying bacteria and fungal populations decreased initially at concentrations of 100 to 300 μg/g but recovered rapidly to levels similar than those in the control.
The effect that pesticides have on trace gas production and consumption in agricultural soils is often overlooked. Independent field and laboratory experiments were used to measure the effects that the commonly used herbicides prosulfuron and metolachlor have on trace gas fluxes (CO2, N2O, and CH4) from fertilized soil of the Colorado shortgrass steppe. Separate sample plots (1 m2) on tilled and no-till soil at the sites included the following treatments: 1) a control without fertilizer or herbicide, 2) a fertilized (NH4NO3 equivalent to 244 kg ha-1) control without herbicide, 3) and fertilized plots amended with an herbicide (prosulfuron equivalent to 0.46 kg ha-1 57% by weight active ingredient or metolachlor equivalent to 5.7 L ha-1, 82.4% by weight active ingredient). During an initial study of one year duration, measurement of gas exchange revealed that prosulfuron-amendment stimulated N2O emissions and CH4 consumption by as much as 1600% and 1300% during a single measurement, respectively. During a second set of flux measurements beginning in August 2001, more frequent weekly measurements were made during a twelve week period. From this second study an increased N2O efflux and CH4 uptake occurred after a 7-week lag period that persisted for about 5 weeks. These changes in gas flux amounted to an overall increase of 41% and 30% for N2O emission and CH4 consumption, respectively. The co-occurrence of stimulated N2O and CH4 fluxes suggests a similar cause that is related to prosulfuron degradation. Evidence suggested that prosulfuron degradation stimulated microbial activity responsible for trace gas flux. Ultimately, prosulfuron-amendment led to an ~50% reduction in the global warming potential from N2O and CH4 fluxes at this field site, which is equivalent to a reduction of the global warming potential of 0.18 mols CO2 m-2 d-1 from these gases. Metolachlor application did not significantly affect the trace gas fluxes measured. These results demonstrate the potential impact that pesticides have on trace gas fluxes from agricultural soils, which could mean that the effects of other agricultural practices have been over or under estimated.
The total and the ureolytic microflora in black spruce humus from an untreated plot and from a plot fertilized with 450 kg urea‐N per ha (400 lb N per acre) 2 years before sampling was studied using incubation tests. Following the addition of 3,500 ppm of urea‐N in the laboratory the total numbers of bacteria and fungi increased on the average by 332 and 9.6%, respectively, and the numbers of ureolytic bacteria and fungi increased by 359 and 18.5%, respectively. The percentages of ureolytic bacteria and fungi both increased by only 5, indicating that the increase in population was not made up of specifically ureolytic organisms. No significant population changes occurred after 3 days of incubation, when urea hydrolysis was complete.
The application of urea in the laboratory to humus from a plot treated with urea two years before sampling brought about population changes which roughly paralleled those found in humus from the untreated plot.
In any particular humus layer, the population increase occurring in the field during the two years after urea application was observed to be in general greater than that occurring during the 42 days after the application of urea to the same humus layer in the laboratory.
Applying enzymes to transform or degrade pesticides is an innovative treatment technique for removal of these chemicals from polluted environments. Enzyme-catalyzed degradation of a pollutant by a parathion hydrolase may be more effective than existing chemical methods. Removal of certain pollutants (for instance phenols and aromatic amines) from wastewater may be achieved by applying phenoloxidases that can convert these chemicals to water-insoluble polymers that can then be removed by filtration or sedimentation. Another decontamination method involves the enzyme-catalyzed incorporation of pesticides into organic matter. This procedure reduces the amount of leachable pesticides as well as the toxicity and bioavailability of the chemicals. Pesticide-detoxifying enzymes must be immobilized before they can be used in the environment. In spite of promising potential applications, very few enzymes have been tested as possible tools in the detoxification of pesticides. Research in this domain can contribute greatly to developing new methods for pollution control.
In the multiple cropping systems used for bean (Phmeolus vulgaris L.) production in Latin America, seed treatment Is often needed for control of soil pathogens and pests, but can be incompatible with Rhizobium inoculation. This study looks at the interaction between Rhizobium and seed protectant. One laboratory and three field studies are reported. The survival of R. phaseoli on bean seeds treated with PCNB, thiram, or captan was measured under laboratory conditions using standard serial dilution and plate count techniques. At Popayan, Colombia (typic dristandept, pH 4.8) the nodulation and nodule development of bean seeds treated with PCNB, thiram, captan, and furadan was evaluated, and different inoimlation methods, including a granular soil applied inoculant, compared. Nodulation of beans protected with PCNB or thiram, and inoculated with seed or soil-applied rhizobia was also studied at La Selva, Colombia (typic dristandept, pH 5.1).
While contact with PCNB, thiram or captan on seeds reduced Rhizobium survival, with captan most toxic, PCNB-treated seeds maintained counts of l0³ rhizobialg seed until almost 48 hours after inoculation. Field results demonstrated the delicate balance between inoculant and seed protectant. At Popayan, nodule number/plant was not affected when thiram, furadan, or PCNB-treated seeds were inoculated and promptly planted, but delay between inoculation and planting did reduce the nodulation of seeds protected with PCNB or thiram. At La Selva, all fungcide treatments lowered nodule number/plant. Seed protection with PCNB enhanced nodule development at Popayan and reduced root rot incidence at La Selva. Despite the somewhat acid soil conditions the best nodulation at both Popayan and La Selva was attained with granular soil-applied inoculants. Further studies on this method of inoculation for beans are warranted.
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The effect of a new pesticide, acetamiprid, applied at normal field concentration (0.5 mg kg -1 dried soil) and at high concentration (5 and 50 mg kg -1 dried soil), on soil enzyme activities and soil respiration in upland soil was studied. The results showed that acetamiprid had a strong negative influence on soil respiration and phosphatase activity, and the enzyme activities in soil treated with 5 and 50 mg kg -1 dry soil were significantly (P < 0.05) lower than the CK over the course of incubation. The 7-, 14-, and 35-day EC10 for phosphatase were 11, 15, and 11 mg kg -1 dry soil, respectively. The 21-day EC10 and EC50 for soil respiration was 0.005 and 83 mg kg -1 dry soil. The activity of dehydrogenase was enhanced after acetamiprid application for 2 weeks and the enzyme activities in samples treated with 0.5, 5 and 50 mg kg -1 dry soil was about 2.5-, 1.5- and 2-fold to that of the control on sample day 28. Variance of urease and catalase had no distinct relationship with the application concentration. The activity of proteinase was not significantly affected within the first 2 weeks but inhibited from the fourth week after acetamiprid application and was only 0.45-fold to that of the control on sample day 28. Overall, acetamiprid at normal field dose would not pose a toxicological threat to soil enzymes, but a certain potential threat to soil respiration.
A laboratory experiment was conducted to study the impact of metalaxyl application at different concentration levels on microbial biomass and the biochemical activities in soil. A dissipation study of metalaxyl highlighted 52.5–56.8% loss of metalaxyl due to the presence of microbial activity. However, a small but significant decline in microbial biomass was observed on 60d of incubation period. Metalaxyl showed a highly significant effect in decreasing total N and organic C content in soil from 0 to 30d of incubation. Dehydrogenase, phosphatase, urease, arylsulphatase and β-glucosidase activities were monitored in metalaxyl treated soils. Except urease, all the enzymatic activities initially increased and then decreased. Urease activity showed a continuous gradual decrease throughout the experimental period. Thus, metalaxyl might influence the growth and development of crop-plants, since it has direct impact on nutrient recycling and energy flow in soil.
l-Glutaminase [l-glutamine amidohydrolasc, EC 3.5.1.2] catalyzes the hydrolysis of l-glutamine to produce ammonia and l-glutamic acid. We have detected this enzyme in soils. A simple, precise, rapid and sensitive method to assay its activity is described, which involves determination of the NH+4 released by l-glutaminase activity when soil is exposed to l-glutamine, Tris(hydroxymethyl)aminomethane (THAM) buffer and toluene at 37°C for 2 h. The NH+4-N released is determined by treatment of the soil sample with 2.5 m KCl containing a l-glutaminase inhibitor (Ag2SO4) and steam distillation of an aliquot of the resulting soil suspension. The optimum pH for NH+4-N released by l-glutaminase activity in soils was 10. l-Glutaminase was saturated with 50 mml-glutamine and the reaction essentially followed zero-order kinetics. The d-isomer of glutamine was hydrolyzed in soils at only 7% of the activity of the l-isomer at saturating concentrations of the substrate. The l-glutaminase reaction in soils was not inhibited by the presence of 5mm NH+4 or l-glutamic acid. The optimal temperature for soil l-glutaminase activity was at 50°C and denaturation began at 55°C. The activation energy values of this enzyme, calculated from the Arrhenius plot, ranged from 20.3 to 39.9 (av. = 32.4) kJ mol−1. Application of three linear transformations of the Michaelis-Menten equation showed that the Km values of l-glutaminase in nine soils ranged from 8.2 to 38.6 (av. = 21.7) mm and the Vmax values ranged from 43 to 854 μg NH+4-N released g−1 of soil 2h−1. The Q10 values ranged from 1.19 to 1.85 (av. = 1.49). Among the various treatments that affected l-glutaminase activity in soils, autoclaving (121°C, 1h), formaldehyde (1ml 5 g−1 soil), dimethytsulfoxide (1 ml 5g−1 soil) and NaF (5mm) reduced the activity by 92, 96, 78 and 14%, respectively. l-Glutaminase activity was greater in toluene treated soils than in untreated soils. The use of sulfhydryl reagents indicated that a free sulfhydryl moiety was required to maintain the active enyzme. Both Ca2+ and Mg2+ (5mm) activated l-glutaminase activity in soils by an average of 4 and 12%, respectively.