Impact of Fertilizers and Pesticides on Soil Microflora in Agriculture

Soil health management is crucial for ensuring sustainable agricultural productions and maintenance of biodiversity. Fertilizers and pesticides are a necessary evil for industrial agriculture. Though, they continue to be critically important tools for global food security, their undesirable effects cannot be overlooked particularly when sustainable agriculture is the universal focus. Apart from a range of widely discussed and well-known adverse effects of chemical fertilizers and pesticides on environment and human health they have also been held responsible for strongly influencing the microbial properties of soil. Soil microflora is a key component of agricultural ecosystems that not only plays a significant role in the basic soil processes but is also actively involved in enhancing soil fertility and crop productivity. Microbial activity in soil has a strong impact on its physical properties and at the same time it is also instrumental in pursuing eco-friendly practices like bioremediation and biocontrol of phytopathogens in agricultural soils. Soil microorganisms have thus been accepted as the bioindicators of soil health and activity. Fertilizers and pesticides tend to have long persistence in the soil so they are bound to affect the soil micoflora thereby disturbing soil health. Amendment of soil with fertilizers and pesticides strongly influences a range of soil functions and properties like rhizodeposition, nutrient content of bulk and rhizospheric soil, soil organic carbon, pH, moisture, activities of soil enzymes and many others. All these factors indirectly lead to a shift in the population dynamics of soil microflora along with the direct effects of fertilizers and pesticides such as toxicity and altered substrate availability profile of the soil. Though such effects are variable depending on many biotic and abiotic factors ranging from soil characteristics to crop variety, still it has been well established that long term and excessive chemical inputs in soil undoubtedly influence the soil microbial communities in terms of their structural and functional diversity as well as the dominant soil species. Here, we review the impact of long term usage of fertilizers and pesticides on the soil microflora of cultivated soils in relation to soil health and fertility, their persistence level in soil, factors affecting their toxicity and pesticide degradation.