Heavy Metal and Phosphorus Contents of Jew's Mallow (Corchorus olitorius L.) Plants Grown on Soil Amended with Phosphate, Bio and Organic Fertilizers

This study was conducted to assess the impact of different chemical, organic and bio fertilizers on growth, phosphorus and heavy metal (Zn, Cd, Co, Cu and Ni) contents of Jew's mallow (Corchorus olitorius L.) plants. Pot and field experiments were carried out in the screen house and experimental farm, Faculty of Agriculture, South Valley University, Egypt in the summer season of 2013 and 2014, respectively. The experimental treatments included rock phosphate, superphosphate and triple superphosphate fertilizers singly or in combination with phosphate dissolving bacteria (PDB) and/or filter mud cake (FMC) as biological and organic amendment to the soil. They had a completely randomized design and complete block randomized design with three replications for pot and field experiment, respectively.

The results of both experiments showed that, although the second and third cuts gave greater plant growth than that of the first cut, only the first cut of the plants received rock phosphate fertilizer either alone or in a combination with PDB and FMC or their mixture contained the lowest level of heavy metals. The results indicated that, only in the first cut with plants receiving rock phosphate fertilizer either alone or combined with PDB, FMC and PDB+FMC recorded the lowest Zn content values of 45.0, 56.0, 64.0 and 94.0 mg / kg, respectively which were below permissible limit, while the second and third cut Zn concentration in plants with different combination treatments was higher than the permissible levels. Also, rock phosphate treatment alone or with PDB in the first cut showed lowest plant Ni content (10 mg/kg) which on the border of the permissible level. The cobalt level in C. olitorius plants that received all phosphate fertilizer types (ranged from 7.0 to 16 mg/Kg) were below the permissible limit. The Cu level in investigated plants received all phosphate fertilizer types with different combination treatments with the three cuts were within the acceptable range. Also the results showed that plants grown on the soil amended with natural rock phosphate alone or in combination with phosphate dissolving bacteria recorded lowest Cd values. It is recommended to use the natural rock phosphate in combination with phosphate dissolving bacteria for growing Jew’s mallow plants instead of chemical phosphate fertilizers and the plants should be harvested by pulling the whole plant including roots from the soil after 40 days from planting to avoid high heavy metal uptake by the plants of the second and third cuts which had a possible health impacts.