Location: Sustainable Perennial Crops LaboratoryTitle: Evaluation of soil amendments as a remediation alternative for cadmium contaminated soils under cacao plantations
|CHAVEZ, E - University Of Florida|
|HE, Z - University Of Florida|
|STOFFELLA, P - University Of Florida|
|MYLAVARAPU, R - University Of Florida|
|LI, Y - University Of Florida|
Submitted to: Environmental Science and Pollution Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2016
Publication Date: 5/27/2016
Citation: Chavez, E., He, Z.L., Stoffella, P., Mylavarapu, R., Li, Y., Baligar, V.C. 2016. Evaluation of soil amendments as a remediation alternative for cadmium contaminated soils under cacao plantations. Environmental Science and Pollution Research. 23:17571-17580.
Interpretive Summary: Soils in some cacao growing regions tend to contain high levels of cadmium. Elevated plant-available cadmium in soils can be toxic to crop production. Accumulation of cadmium in cacao beans reduces their quality and marketability. Amendments to soils can help by reducing plant bio-available cadmium. In this paper we report laboratory incubation studies to assess the effectiveness of soil amendments in reducing plant available cadmium in three cacao-growing soils from Ecuador. Of the two amendments tested, vermicompost significantly reduced the plant available cadmium in the tested soils with low cadmium sorption. This information will be of use to farmers and extension workers using suitable amendments during remediation of soils that have high levels of cadmium. Reduction of cadmium levels in cacao beans will improve market values and increase incomes of resource poor cacao farmers.
Technical Abstract: Elevated plant-available cadmium (Cd) in soils results in contamination to cacao (Theobroma cacao L) beans. Effectiveness of vermicompost and zeolite in reducing available Cd in three cacao-growing soils was studied under laboratory conditions. Sorption-desorption experiments were conducted in soils and amendments. Cadmium was added at 0 or 5 mg kg-1 (spiked), then, amendments were incorporated at 0, 0.5 or 2%. Amended soils were incubated at room temperature for 28 d. Plant-available Cd was determined using 0.01 M CaCl2 (WSE) and Mehlich 3 (M3) extraction procedures in subsamples taken from individual bags at six time intervals. Soils and amendments displayed different sorption characteristics and a better fit was attained with Freundlich model (R2 > 0.82). Amendments were ineffective in reducing extractable Cd in nonspiked soils. In Cd-spiked soils, vermicompost at 2 % significantly reduced WSE-Cd (P < 0.01) from 3.36, 0.54, and 0.38 mg kg-1 to values lower that instrument’s detection in all the three soils and significantly diminished M3-extractable Cd (P < 0.05) from 4.62 to 4.11 mg kg-1 in only one soil. Vermicompost at 0.5% significantly decreased WSE-Cd (P < 0.01) from 3.04 and 0.31 to 1.69 and 0.20 mg kg-1, respectively in two soils with low sorption capacity for Cd. In contrast, zeolite failed to reduce WSE- or M3-extractable Cd in all studied soils. A negative correlation occurred between soil pH and WSE-Cd (r > - 0.89, P < 0.01). The decrease in WSE-Cd appears to be associated with the increase in pH of the vermicompost-amended soils.