## 3 Results
### C and N Dynamics in Soil with MPs: Enzymatic Indicators  
Microorganisms and their enzymatic activities play crucial roles in the soil nutrient cycle and are, therefore, related to crop nutrition. Consequently, it is important to include the determination of enzymatic indicators, which provide rapid information on the conditions in which the metabolic activity of the microorganisms present in the soil develops [61]. In this regard, UA, DHA, and FDA in the presence of MPs presented similar results, without significant differences between the treatments (\(p>0.05\)), establishing the following order in enzymatic activity: T1 = T2 = T3 = T4 (Figure 5A-C). Nonetheless, it is important to emphasize that the FDA activity in treatment T4 presented a concentration that was 30.43% higher than that of T2. [PERSON] et al. [79], in a meta-analysis study that included 1812 investigations on the enzymatic activities of soil and MPs, concluded that MPs do not significantly affect (\(p>0.05\)) the enzymatic activities in soil. These results are similar to those found in the present study. However, [PERSON] et al. [15] used MPs of polyamide (PA), PE, and PES, finding that these especially increased the FDA enzymatic activity. On the other hand, when using PET, PP, and polystyrene (PS), no change in the activity of this enzyme was observed. Moreover, [PERSON] et al. [73] determined that 28% (w w\({}^{-1}\)) of PP in the soil increased the FDA activity, but at a concentration of 7% (w w\({}^{-1}\)), there was no significant difference (\(p>0.05\)). It has been found that MPs such as PP can increase the activity of enzymes--e.g., \(\beta\)-Glucosidase, Acid phosphatase, and FDA--probably because the CH\({}_{3}\) side of the PP chain is easily destroyed through various biochemical processes [80,81]. In the present study, an increase in FDA enzymatic activity could only be established when comparing the treatments that had the highest and lowest concentrations of PP, with the FDA of T4 being significantly higher than that of T2 (\(p\leq 0.05\)). This behavior may be related to the dose of MPs in the soil, which could promote a better disposition of OM for soil microorganisms [73]. In the same context, [PERSON] et al. [4] found no significant differences (\(p>0.05\)) in the UA and DHA activities in soils with 0.002% (w w\({}^{-1}\)) of high-density polyethylene (HDPE) compared to a control soil. However, these researchers noted differences in the DHA activity when adding cadmium (Cd) in combination with MPs to the design of the experiments. They found that Cd treatment decreased the activity of this enzyme by binding Cd and its functional groups, such as hydrogen sulfide, carboxyl, and imidazole. Perceiving these differences was possible because DHA is one of the enzyme bioindicators that is most sensitive to heavy metal contamination [4,82]. It is important to note that DHAmainly involves anerobic soil microorganisms, most abundantly in the genus _Pseudomonas_, particularly in _Pseudomonas entomophila_[83]. On the other hand, despite the fact that UA is related to the N cycle in soil--as it promotes the hydrolysis of OM containing N--it can be concluded that the high concentration of N\({}_{\rm min}\) in the different treatments of the present study may have been an important reason why a higher concentration of this enzyme (UA) was unnecessary for N mineralization and, therefore, did not present significant differences between treatments (\(p>\) 0.05). [PERSON] et al. [7] indicated that urease activity was significantly correlated with some bacterial genera, such as _Aeodermatiphilus_, _Blastococcus_, _Bacillus_, _Marmoricola_, and _Nitrospira_. In a study by [PERSON] et al. [84], where enzymatic activity was related to the microorganisms present in soil, they showed that soil fungi and actinomycetes were strongly positively correlated with protease, urease, and Acid phosphatase, indicating that the interaction of microorganisms and soil enzymes is significant for improving soil fertility.