Molecular Soil Biology 2024, Vol.15, No.3, 118-128 http://bioscipublisher.com/index.php/msb 120 al., 2021). In Northern Italy, the presence of oxadiazon in water from both conventional and organic rice paddies was identified as a major cause of toxicity, demonstrating the widespread impact of pesticide use even in organic farming systems. Another study in Pakistan revealed significant health issues among rice farmers due to pesticide exposure, including skin and eye irritation, cough, dizziness, and even cases of serious illness and death (Elahi et al., 2019). These case studies underscore the need for better management practices and stricter regulations to mitigate the adverse effects of pesticide use in rice cultivation. 3 Types of Pesticides Used in Rice Cultivation 3.1 Insecticides, herbicides, fungicides Rice cultivation employs a variety of pesticides to manage pests, weeds, and diseases. The primary categories of pesticides used include insecticides, herbicides, and fungicides. Insecticides target insect pests, herbicides control weed growth, and fungicides prevent fungal diseases. 3.2 Common active ingredients and their functions Several active ingredients are commonly used in rice cultivation for their effectiveness. Common active ingredients in insecticides include imidacloprid and chlorpyrifos. Imidacloprid is widely detected in rice fields and is known for its effectiveness against a broad spectrum of insect pests. Chlorpyrifos, although effective, has significant non-target effects on soil microbes and nematodes (Kumar et al., 2017). Penoxsulam and profoxydim are newer generation herbicides used in rice paddies. Penoxsulam is particularly persistent in water, while profoxydim dissipates quickly. Butachlor is another widely used herbicide, known for its effectiveness in controlling weeds. Tricyclazole and carbendazim are common fungicides. Tricyclazole is highly persistent in soil, making it effective for long-term fungal control (Tsochatzis et al., 2013; Wandscheer et al., 2017). Carbendazim is frequently detected in rice-vegetable rotation systems and poses a risk of water contamination. 3.3 Usage patterns and application methods The application of pesticides in rice cultivation varies based on the type of pest, weed, or disease being targeted, as well as the environmental conditions. Insecticides like imidacloprid are often applied during specific crop stages to maximize effectiveness against pests. Chlorpyrifos is applied regularly but has a short half-life, necessitating frequent applications. Herbicides such as penoxsulam and profoxydim are applied under submerged conditions typical of rice paddies. The dissipation rates of these herbicides vary, with penoxsulam persisting longer in water. Butachlor is applied more frequently in regions with direct seeding methods (Dash et al., 2018). Fungicides like tricyclazole are applied to manage fungal diseases, with application rates and timing adjusted to ensure persistence in the soil. Carbendazim is applied in rotation systems, with its residues frequently detected in both soil and water (Tan et al., 2020; 2021). These usage patterns and application methods are critical for managing the environmental impact of pesticide use in rice cultivation, ensuring effective pest control while minimizing risks to soil and water health. 4 Impact of Pesticides on Soil Health 4.1 Soil contamination and residue persistence Pesticide residues in soil are a significant concern due to their persistence and potential to cause long-term contamination. Studies have shown that continuous application of pesticides like chlorpyrifos can lead to residue accumulation, although the persistence may vary. For instance, chlorpyrifos residues in rice field soil were found to dissipate significantly within 15 days, with a half-life of approximately 4.02 days, indicating that while residues are present, they may not be highly persistent in certain conditions. However, other studies have highlighted the presence of multiple pesticide residues in agricultural soils, with some compounds like glyphosate and DDTs being found at high concentrations and persisting in the environment (Silva et al., 2019). 4.2 Effects on soil microbial diversity and function Pesticides can have profound effects on soil microbial communities, which are crucial for maintaining soil health and fertility. Long-term pesticide application has been shown to reduce the abundance and diversity of key microbial groups. For example, continuous use of chlorpyrifos significantly reduced populations of
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