Biomass production and heavy metal content of Rosmarinus officinalis grown on organic waste-amended soil

This paper reports the effects of organic waste compost on Rosmarinus officinalis growth in pots containing degraded soil. Dried biosolid compost (B-C) and municipal solid waste (MSW-C) were mixed with soil at doses of 0, 20 or 40 Mg ha−1. The plants were harvested before anthesis and biomass production and rosemary oil production determined. The macronutrient, micronutrient and heavy metal contents of the aerial parts of the plant were analysed to determine nutritional status and heavy metal accumulation. All the biowaste treatments increased soil fertility. Biomass production increased significantly when plants were grown in the biowaste-treated soils. No significant differences were seen among the different treatments with respect to oil production. Plants grown on amended soils showed a general improvement in their macro- and micronutrient status, yet their heavy metal (Pb, Cr and Ni) contents did not increase significantly. The concentration of heavy metals found in the leaves would not significantly increase their transfer from the soil to humans via the food chain. Biowaste composts can be safely applied to degraded soils at a dose of 40 Mg ha−1 without the risk of adverse environmental effects. MSW-C is better applied at a dose of 20 Mg ha−1.