Evaluation of phytoextractor plants and dolomite lime as strategies to manage Cd in soils growing cacao (Theobroma cacao L.) and spinach (Spinacia oleracea)
Open Access
- Author:
- Benavides Bolanos, Jhony Armando
- Graduate Program:
- Soil Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 26, 2019
- Committee Members:
- Patrick Drohan, Thesis Advisor/Co-Advisor
Douglas Miller, Committee Member
John Thomas Spargo, Committee Member
Siela N. Maximova, Committee Member - Keywords:
- Phytoextraction
sunflower
cacao
cadmium
soil - Abstract:
- European Commission Regulation (2006) and European Food Safety Authority (EFSA) (2012) legislation setting cadmium (Cd) human ingestion thresholds in food products is now affecting cacao bean (Theobroma cacao L.) production in Latin American countries via the rejection of food products exceeding maximum ingestion threshold levels. Cacao producers must be proactive and minimize Cd uptake by commodities and such strategies must be affordable for low income communities (or countries) where agricultural development is critical to stabilizing socio-political-economic systems. Two potential options for producers include: (a) the use of phytoextractor species, which can remediate some soil pollutants; and (b) metal immobilization via soil pH adjustment. We hypothesize that the use of a Cd phytoextractor species in an intercropping scheme, with the addition of dolomitic lime (to raise soil pH and decrease soil Cd availability), will decrease total Cd uptake in cacao and in spinach plants. The effectiveness of four phytoextractor species was evaluated: Helianthus annuus (sunflower), Brassica napus (oilseed rape), Chyrsopogon zizanioides (vetiver), and Heliconia psittacorum (heliconia). The efficacy of a combined phytoextraction and immobilization (per the use of dolomitic lime to raise soil pH) strategy was assessed. This research is divided in five chapters. The first chapter is the introduction and problem statement. The second chapter is the literature review. The third chapter describes three Cd dose-response experiments. Experiment 1 and 2 were conducted at The Pennsylvania State University (US) and evaluated the Cd extraction ability of sunflower, oilseed rape, and vetiver cultivated in a soil-less media (play sand and perlite) artificially spiked with Cd. Experiment 2 followed the same scheme as the first, but plants were cultivated in a manufactured soil matrix (soil and perlite) at Penn State. Experiment 3 was conducted at Universidad del Valle (Cali, Colombia) and used sunflower, vetiver, and heliconia cultivated in a natural soil artificially contaminated with Cd. Experiments 1, 2 and 3 were used to determine the most suitable Cd phytoextractor. Results from the experiments reveal that the sunflower presented a high plant aerial tissue total Cd and a high resistance to pest and diseases, in comparison to the other plant species, therefore it is recommended as a suitable Cd phytoextractor. In chapter four, a new set of three experiments was developed. The aim of these experiments was to assess the effect of an intercropping scheme with sunflower (as Cd phytoextractor) and dolomitic lime application (as soil pH modifier) on cacao and spinach Cd accumulation. Results indicate that dolomitic lime application increased soil matrices pH reducing Cd accumulation in cacao (variety IMC-67), but neither the addition of dolomitic lime nor the intercropping scheme with sunflower resulted in a significant reduction on total Cd in plant aerial tissue of spinach (alpha = 0.1). Chapter 5 presents a summary of results and future research.