Elemental characterization of atrazine treated soil pretreated with sawdustbased biochar types using Energy Dispersive X-ray (EDX) spectroscopy

Abstract

The escalating area of degraded farmlands across Africa, attributed to the intensive and indiscriminate use of agrochemicals demands investigation into the speciation of nutrient elements in this herbicide treated soils for devising sustainable management strategies. This study examines the fate of organic carbon, heavy metals, macro and micronutrient compositions in soil treated with atrazine (a widely utilized broad-spectrum herbicide in Africa), both with and without biochar pretreatment using energy-dispersive X-ray (EDX) spectroscopy. Elemental characterization of soil treated solely with atrazine (at 2.5 kg active ingredient/ha) was evaluated under screenhouse condition when factorially combined with four sawdust (SD)-based biochar: SD pyrolyzed with or without poultry manure (PM) at 350℃ (tagged SD+PM@350 and SD-PM@350 respectively), and SD pyrolyzed with or without PM at 450℃ (tagged SD+PM@450 and SD-PM@450 respectively). Each biochar was applied at 5 and 10 t/ha, equivalent to 2.37 and 4.75 g/950 g soil, respectively.An absolute control soil, that received neither atrazine nor biochar was included. Soil samples collected from appropriately treated soil after two successive maize cropping were analyzed for total metal concentrations using EDX spectroscopy after sputtering each sample with gold on aluminum stubs. Significant (p < 0.05) enrichments of Cu, Ni, and Pb by
215%, 165%, and 222%, respectively, were observed in sole atrazine treated soil which were absent (0 ppm) in similar atrazine-treated soils pretreated with SD+PM@350 and SD+PM@450. Similarly, total C decreased by 10% and 17% in sole atrazine and absolute control soils respectively, compared to the baseline value. Biochar pretreatment however, increased total C by a range of 24.5 to 35.9%. Higher percentages of total N, P, Mg, and K were, however, observed in sole atrazine treated soil relative to the baseline and absolute control values, with the total Mg and K contents exceeding those observed in biochar-pretreated soils.
Continued sole atrazine use, therefore, poses potential risks of carbon depletion and heavy metal toxicities in the soil studied. Pretreating soils with sawdust-based biochar, therefore, offers mitigation strategy against these environmental and sustainability risks in soils annually receiving atrazine herbicides.