Heavy metals in Cucumber (Cucumis sativus L.) as influenced by Organic and Inorganic Fertilisers

Abstract

Heavy metals are significant environmental contaminants found on the surface and in the tissue of fresh vegetables through the use of phosphate and animal manure fertilisers applied to soil during production. A field study was carried out at the experimental site of National Horticultural Research Institute, Idi-ishin, Ibadan, to assess the heavy metal concentration in cucumber planted under different levels of phosphate (synthetic) and animal manure (organic) fertilisers. There were five treatments: Poultry manure,Composted cow dung, Liquid Organic fertiliser, NPK (15:15:15) and the control which were laid out in a randomised complete block design replicated three times. Data were collected on growth and yield parameters; plant height (PH), stem girth (SG), leaf area (LA), number of fruits (NOF) and fruit weight (FW) of cucumber. Heavy metal analysis was carried on all the fertilisers before use, on the soil and fruits after harvesting using standard procedures. Risk Assessment to human exposure was also determined. Data were analysed using ANOVA at p<0.05.Results were compared with the WHO and EU standards. The findings were used to determine the Daily Intake of Metals (DIM), the Health Risk Index (HRI) and the Target Hazard Quotient (THQ). The HRI and THQ for Lead were highest in compost (0.45) and (0.88) respectively although it is still below the tolerable limit (1). If used over time or eaten more often could lead to bio-accumulation and eventually respiratory and other carcinogenic diseases in humans.