Effect of Sewage Sludge Amended Soil on Mineral Nutrition and Metal Accumulation on Sunflower Crop

The aim of the present study was to evaluate the suitability of sewage sludge amendment for sunflower (Helianthus annuus L.) by assessing the biomass measurements, macroelements (N, P, K, Ca, Mg) and potential hazardous metals accumulation (Mn, Cu, Zn, Cd, Ni, Pb) at different doses of sewage sludge accompanied by mineral fertilization. Sewage sludge fertilization produces significant increase of stem and leaves mass, meanwhile significant increases of calatidium mass appear in the case of 200 kg N/ha dose. Nitrogen content in calatidium increased significant after sewage sludge fertilization with doses higher than 200 kg N/ha, and the highest potassium content was registered at 400 kg N/ha dose. Phosphorus content in calatidium presents a great variability and it is not significant influenced by fertilization with sewage sludge, being observed even a downward trend. Calcium and magnesium contents in stem and leaves increases with sewage sludge dose, the highest concentrations being observed at 500 kg N/ha dose. Sewage sludge application produces increases of manganese and copper concentrations in stems and leaves. Manganese and zinc contents found in stems and leaves are higher than in calatidium, meanwhile in copper case was registered the opposite situation. Sewage sludge fertilization produces significant increases of cadmium in stems and leaves at doses higher than 300 kg N/ha but not exceed 1 mg/kg. In small doses (100-300 kg N/ ha), sludge produces an increase of nickel in stems and leaves. Lead accumulation in stems and leaves is produced when applied sewage sludge doses are higher than 300 kg N/ha. There are no concerns regarding environmental issues correlated with elevated levels of metals in sunflower plants.