# Phtyoremediation and Bioremediation of Pesticide-Contaminated Soil
## 6 Pesticides and Soil Ecology  
One aspect of soil ecology is biodiversity of soil fauna. In healthy soils there are bacteria, fungi, protozoa, nematodes, arthropods, and earthworms. Bacteria and fungi are important for biodegradation of pesticides and other organic matter [59; 114; 191; 190; 200]. Arbuscular mycorrhizal fungi are associated with plant roots and rhizodegradation, and they improve ecological health [115; 218]. Symbiotic fungi are beneficial for plants in contaminated soil, and they have a positive impact on pesticide degradation in the rhizosphere [116; 187]. Mycorrhizal colonization of roots results in an increase of root surface area and enhances nutrient acquisition for plants [218; 295]. Microbial endophytes protect plants and contribute to plant tolerance to herbicides [232] while rhizosphere-associated bacterial populations enhance pesticide degradation [references cited in 122; 133; 305]. Nematodes, arthropods, and earthworms are beneficial in soil as indicator organisms, organic matter degraders, and soil structure modifiers [49; 93]. The populations of these organisms are negatively affected by some pesticides [41; 62; 93].  
Before pesticides are released on the market, thorough testing of their active ingredients' ecotoxicological effects must be performed to evaluate whether the risk is at an acceptable level [300; 304]. However, numerous studies are reporting the toxicity of pesticides on soil ecosystems [41; 48; 100]. These effects fall into three general categories: inhibition of microbial functions, reduction of microbial group abundance, changes in the composition and diversity of soil microbial communities. Reviewsby [PERSON] (1985) and [PERSON] (1991) provide a general overview of the response of soil microorganisms to pesticides. It should be noted that [PERSON] concluded that the usage of the recommended dosage and other good agricultural practices would help to minimize their detrimental effects on microorganisms and suggested further promoting policies focused on implementation of these practices. Researchers, as well as organizations such as European Food Safety Authority (EFSA), recently pointed out the need for new tests to better evaluate the impact of pesticides on soil microbial communities as well as overall soil quality ([PERSON], 1991; [PERSON], 1991).  
Numerous studies focus on the effects of pesticides on specific groups of soil biota ([PERSON], 1991; [PERSON], 1991). For instance, the effects of pesticides on earthworms have been reviewed recently ([PERSON], 2017). Damage to DNA, changes in enzyme activity and altered membrane stability have been reported. For earthworms, the most harmful families of pesticides are carbamates, nicotinoids, organophosphates, strobilurins, sulfonylurea, and triazoles ([PERSON], 2017). Earthworm, nematode, and protozoa populations may be reduced by application of herbicides ([PERSON], 2017). [PERSON] et al. (2017) cite half a dozen examples of major non-target impacts on flora and soil fauna from a range of common pesticides.  
Microbial biomass in soils is a good measure of soil quality ([PERSON], 2017). [PERSON] has reviewed the literature on the effects of 21 pesticides on soil microorganisms, and concluded that it is difficult to predict organism responses from knowledge of pesticide chemistry ([PERSON], 2017). Beneficial microbial communities are important in crop production but their effectiveness can be reduced by pesticide application ([PERSON], 2017; [PERSON], 2017; [PERSON], 2017). Mycorrhizal fungi associated with roots are negatively affected by application of fungicides; in situ activity of enzymes such as dehydrogenases which are linked with microbial respiratory processes, may be affected by pesticide applications, and there may be interactive effects on soil biota when more than one pesticide is applied ([PERSON], 2017).