Cadmium in Soils Cultivated with Avocado in Peru: Interaction with Soil Variables and Its Relationship with Parent Material

The presence of cadmium (Cd) in agricultural soils poses an increasing threat to the sustainability of production systems and the safety of avocado (Persea americana) cultivation in Peru. This study aimed to assess the total accumulated Cd content in soils under avocado cultivation and its association with edaphic, geochemical, and geomorphological variables. A total of 410 soil samples from various avocado-growing regions in Peru were analyzed for 26 physicochemical properties, 22 total metal concentrations, and 6 geospatial variables. Data analysis included: (1) univariate statistics (skewness, kurtosis); (2) multivariate methods such as Spearman correlation and principal component analysis (PCA); (3) spatial modeling using the Geodetector tool for variance partitioning; and (4) non-parametric testing (Kruskal–Wallis with Dunn’s post hoc test). The results indicated: (1) the presence of hotspots with Cd concentrations exceeding 3 mg·kg⁻¹, displaying a leptokurtic distribution (skewness = 7.3); (2) dominant accumulation mechanisms involving co-adsorption and cation competition (Na⁺, Ca²⁺), as well as geogenic co-accumulation with Zn and Pb; and (3) significantly higher Cd concentrations in Leptosols derived from Cretaceous intermediate igneous rocks (diorites/tonalites), averaging 1.33 mg kg⁻¹, compared to 0.20 mg·kg⁻¹ in alluvial soils (p < 0.0001). The factors with the greatest explanatory power (q > 15%, Geodetector) were Zn content, parent material, geological age, and soil taxonomic classification. These findings provide edaphogenetic insights that can inform soil Cd management strategies, including the recommendation to avoid establishing new plantations in areas with a high risk of Cd accumulation. Such approaches can enhance the efficiency of mitigation programs and reduce risks to export markets.