Impact of Fertilizer, Herbicide, Algicide and Fungicide on Soil Microbial and Enzyme Activities in Maize and Rice Ecosystem

To increase crop productivity, modern agricultural practices comprise fertilisers, algaecides, herbicides and fungicides. Fertiliser application profoundly impacts soil microbes and enzymes, with organic fertilisers generally promoting beneficial microbial communities and enzyme activities like phosphatase and dehydrogenase, while high-dose inorganic fertilisers can lead to negative effects, such as reduced microbial richness and inhibition of certain enzyme activities, often altering soil nutrient availability and pH. Long-term studies show that organic amendments can enhance microbial biomass and functional diversity, supporting nutrient cycling, while mineral fertilisers, especially in excess, may negatively affect soil health and microbial respiration. Fungicide application negatively impacts soil health by reducing microbial biomass, decreasing fungal populations, altering microbial community structure, and inhibiting enzyme activities, such as phosphatases, dehydrogenases, and ureases. These effects disrupt soil fertility and ecological functions, although the specific impact depends on the fungicide's type, dose, persistence, and soil conditions. Algicide application can negatively impact soil microbes and enzyme activities, decreasing microbial populations and altering community structure due to toxicity, while simultaneously affecting key enzymes like urease, phosphatase, and catalase involved in nutrient cycling and organic matter breakdown. However, studies show a complex relationship, with algicides sometimes causing an initial increase in certain microbial populations before a decline, highlighting the importance of application rates and exposure time. The overall effect can lead to reduced soil fertility and long-term ecological consequences. Herbicide application generally alters soil microbial communities and enzyme activities, often with an initial inhibitory effect on microbial respiration and enzyme activity, though this can be temporary. The specific impact varies significantly based on the herbicide's type, dose, and soil conditions. Some herbicides can be particularly detrimental to beneficial microbes, slowing crucial processes like nitrogen cycling, while others may promote the growth of specific microbes involved in herbicide breakdown. Combined herbicide applications often intensify negative effects, and long-term exposure can shift microbial community composition and function, influencing soil health and fertility.