Global Journal of Science Frontier Research, D: Agriculture and Veterinary, Volume 23 Issue 1

following order Mn ˃ Zn ˃ Cu ˃ Pb ˃ As ˃ Cd (Table 3). Data from this analysis indicated that values of all heavy elements were primarily low and within specified guidelines of FAO/WHO (2011) and National Environmental Standards and Regulations Enforcement Agency (NESREA, 2018) values for arable land. The variation of heavy elements content in the research area was also owing to inorganic fertilizer and the like agronomic practices. The low content of the rich components of the cropland may have resulted from their continuous removal by staple food crops grown in the chosen areas. Among the different elements analyzed in soil, the content of Mn was the highest, and variation in its content was many times exceeding those described by Ogunwale et al. (2020). The most elevated deposition of Mn in cropland soil might be a result of its long-term utilization in the production of agricultural implements, paints, pigments, pesticides, insecticides, and alloying of varied farms of the investigated area that might give rise to pollution of the soil and an effect in tillage. Despite what preceded, it was found from the analysis of the data that regardless of the low element contents, there was significant burdening or bioaccumulation of heavy elements in soils from arable land areas as indicated by the evaluated heavy element pollution load index (HEPLI) in Table 6 below. On the basis of Ogunwale et al. (2021), HEPLI is the degree of pollution per element in farmland soil relative to a recommended content (world benchmark levels of elements in shale/rock). If it is more than one, then there is significant element enrichment in the soil of interest. The overall mean indices of HEPLI for elements assessed in this analysis for both seasons were 0.54 and 0.88, 0.28 and 0.92, 0.31 and 0.37, 0.52 and 0.55, 0.28 and 0.55 and 0.24 and 0.31 for As, Cd, Cu, Mn, Pb, and Zn, respectively, with the rate of amassment being in this order for the wet season As ˃ Mn ˃ Cu ˃ ˃ Cd, Pb ˃ Zn and for dry season Cd ˃ As ˃ ˃ Mn, Pb ˃ Cu ˃ Zn. Cadmium and As contained the highest overall mean HEPLI (0.92 and 0.88) while Zn contained the least overall mean HEPLI (0.24 and 0.31) in the soil from the cropland site. The moderate HEPLI indices of elements in the grounds in this analysis revealed substantial loading and an indication of heavy elements buildup (pollution) in the grounds within the areas from extensive farming activities, which is in corroboration with the findings of most earlier studied (Ogunwale et al., 2021;Zango et al., 2013; Zhuang et al., 2009). In this way, comprehensive agricultural operations in the research area caused the raising of the contents of heavy elements in the soil. c) Heavy Element Pollution in Staple Foodstuff Crops The mean contents (in mg/kg dry matter) of heavy elements (As, Cd, Cu, Mn, Pb, and Zn) in the assigned food crops (sweet cassava, maize, plantain, and white yam) in the assessment area were all below values present in their equivalent soils (both farmed and unfarmed soils) as presented in Table 5, showing evidence of heavy element low bioaccumulation in staple food crops. The moderate element contents in the food crops may have been burdened by the noticed rise in heavy element levels as a result of farming operations, as can be inferred from the study of the HEPLI of soils from farmed areas concerning those assessed of unfarmed regions (control) in Table 6. The HEPLIs of all the elements were below 1, signifying insignificant bioaccumulation of elements in soils in the arable land areas. Except for As, the mean contents of all the heavy features quantified in sweet cassava, maize, plantain, and white yam (Table 4) grown in the farmland areas in both seasons below the prescribed values of FAO/WHO (2011). Investigations revealed that food crops tilled on soils present in arable land sites could be polluted with a heavy element like As and so could introduce consumers of that food to severe health hazards (Ogunwale et al., 2021;Zango et al., 2013; Zhuang et al., 2009). The findings found from this research in wet and dry seasons indicated that As in cassava, maize, plantain, and yam were above the standard tolerable limit by the Joint FAO/WHO Expert Committee on Food Additives and Food and Nutrition Board (2011) by 25.00 and 16.23%, respectively. Thereby As signify the primary causes of heavy element pollution in the selected foodstuff crops in the communities in the assessment district with Cd, Cu, Mn, Pb, and Zn and demonstrating insignificant pollutants, and this relates to the findings of Zango et al. (2013) and Zhou et al. (2016). d) Heavy Element Transfer (AF) from Soils to Food Crops In the general case, by sources of agrichemicals, chemicals leaking the water ecosystem, subsequently, enter into the soil. The soil absorbs the portion of the substances which, suitably, turn into part of the photosynthetic processes. It was thus estimated that the contents of elements in the sweet cassava, maize, plantain, and white yam would exhibit the contents in the soil samples. As expressed by Ogunwale et al. (2021), there is a statistical relationship between element contents in rhizosphere soils and grown crops. Nonetheless, the results of this analysis revealed inconsistency. The association between element contents assessed in soils regarding grown food crops was somewhat varied and insignificant. The contents of elements in soils for both seasons was something like Mn ˃ Zn ˃ Cu ˃ Pb ˃ As ˃ Cd while the sequence in BF in both seasons were As ˃ Cd ˃ Zn ˃ Mn ˃ Pb ˃ Cu and As ˃ Zn ˃ Cd ˃ Mn ˃ Cu ˃ Cd ˃ Pb, respectively. Nonetheless, the analysis of the HEPLI on soils in this assay indicated a statistical difference in the sequence of the HEPLI and total element contents in food crops. Cropland Bioaccumulation Risks of Potentially Toxic Elements in Soil of Some Designated Foodstuffs Cultivated in Odu’a Farm Establishment, Aawe, Oyo State, Nigeria 1 Year 2023 1 © 2023 Global Journals Global Journal of Science Frontier Research Volume XXIII Issue ersion I VI ( )D