## 3 Results and Discussion
### Principal Component Analysis (PCA)  
The results of the principal component analysis (Figure 8) indicated that the first two principal components explained 58.76% (PC1) and 33.02% (PC2) of the variance, respectively, accounting for a total of 91.78% of the variance in the original variables. The vectors representing the original variables extend nearly to the edges of the unit circle, suggesting that the two components provide an excellent representation of the variable space (Figure 8a). Soil contaminants (DDT, DDE, DDD, \(\gamma\)-HCH) are distributed in different parts of the PCA plot, which suggests that they have varied impacts on the environment. The concentration of \(\gamma\)-HCH was positively correlated with soil C\({}_{\text{org}}\) content. \(\gamma\)-HCH can bind to soil organic matter, but it can also be gradually released from soil [60]. No significant correlations were noted between C\({}_{\text{org}}\) content and the levels of DDT, DDE, and DDD in soil. According to [PERSON] et al. [55] and [PERSON] et al. [66], the presence of a positive correlation between DDT concentration and total C\({}_{\text{org}}\) content indicates that DDT follows a secondary distribution pattern. DDT and its derivatives are hydrophobic compounds that tend to accumulate in soil organic matter [23]. In the current study, rainfall was negatively correlated with soil DDD levels, which could suggest that these compounds were reached from soil or degraded. A positive correlation was observed between temperature and the presence of \(\gamma\)-HCH in soil. [PERSON] et al. [53] argued that low soil \(\gamma\)-HCH levels could indicate that this contaminant is volatilized under the influence of higher temperatures. The points presented in Figure 8b correspond to individual fertilizer treatment cases in specific cultivation years. The distances between the  
Figure 8: Results of PCA exploring the effect of temperature, precipitation, and C\({}_{\text{org}}\) content on the residual levels of organochlorine pesticides in soil. (**a**) projection of variables and treatments onto the first and second principal components, (**b**) \(\gamma\)-HCH—\(\gamma\)-hexachlorocyclohexane, DDT—1,1,1-Trichloro-bis-2,2 [4-chlorophenylophenyl]-ethane, DDD—dichlorophenoxyyldichloroethane, DDE—dichlorophenyldichloroethylene. points indicate the degree of similarity between the cultivation practices across different years. Based on the data presented in Figure 8b, soil contaminants were divided into four groups corresponding to the experimental years. The results noted in 2017 clearly differed from the data recorded in other years, which suggests that OCP concentrations were influenced by weather conditions (temperature and precipitation), fertilization, and the gradual accumulation of fertilizers in successive years of the study. In the analysis of the effects of temperature, rainfall, grain yield, and lipid content on the concentration of organochlorine pesticide residues in the grain, PCA revealed that PC1 and PC2 accounted for 61.94% and 24.18% of the variance, respectively, representing 86.12% of the total variance in the original dataset. The concentration of \(\gamma\)-HCH in grain was positively correlated with precipitation, but not with temperature (Figure 9a). According to [PERSON] et al. [67], the lipid of \(\gamma\)-HCH in soil is determined by weather conditions, and \(\gamma\)-HCH levels decrease with a drop in temperature and increase in response to abundant rainfall. In this study, the content of DDT and its metabolites in grain was not correlated with precipitation levels in the growing seasons. Grain lipid content was negatively correlated with organochlorine contamination. The accumulation of OCPs in plants is determined by the chemical structure of these compounds as well as plant physiology [21]. Residual pesticides are taken up mainly by roots and absorbed by lipophilic tissues in plants [18].