Trace Metal Elements (Pb, Cd and As), 15N Nitrogen and Phosphorus Isotopes Accumulation in Three Varieties of Tomato from Conventional and Agro-Ecological Farming Systems in Burkina Faso

Tomato is a market gardening product that plays an important nutritional and economic role in Burkina Faso. However, the bad use of pesticides for its production could have negative impacts consumers’ health. The objective of the present study was to assess the concentration of trace metal elements (Pb, Cd and As), 15N isotopes (NO2-, NO3-, NH4+) and phosphorus (PO42-) in tomatoes according to cultivation practices. Thus, three tomato varieties (Mongal F1, F1 Cobra 26 and Roma F1) were grown using organic and conventional production methods on 2 sites at Nongr Massom, (commune of Kadiogo province). The trace metal elements were analyzed using atomic absorption spectrophotometry, the isotopes 15N (NO2-, NO3-, NH4+) and phosphorus (PO43-) using standardized methods. Tomatoes from conventional agriculture had higher levels of trace metal elements (0.163 - 0.298 mg/Kg, 0.082 - 0.146 mg/Kg and 0.018 - 0.032 mg/Kg respectively for Pb, Cd and As) than those from organic agriculture samples. Concentration of trace metal is lower for organic production with a reduction of 19.02%, 19.69% and 20.77% for Pb, Cd and As respectively compared to conventional production. High levels were recorded for the Roma F1 variety. The concentrations of trace metal elements in organic production are lower than the codex standards (2010) while those in conventional production are higher. These results could be due to the use of chemical inputs that could have a negative impact on the nutritional quality of these tomatoes. The concentration of trace metal elements in tomato fruits is strongly correlated by production method and less by the variety (genetic).