Growing media effect on essential and non-essential mineral composition of lettuce

The composition of the environment in which vegetables are grown or their interaction with the applied fertilizer or nutrient solution determines the essential and non-essential element contents of the vegetables. The main purpose of this study is to evaluate variations of essential and non-essential mineral concentrations of lettuce plants (Lactuca sativa L. cv. Sementel) grown under soil and soilless media. The plants were grown in: low calcareous soil (LCS) and high calcareous soil (HCS), or rockwool or cocopeat. The best growth was from plants grown in cocopeat followed by rockwool, LCS, and HCS. Nitrogen, P, and Zn concentrations of rockwool and cocopeat grown plants were higher than in plants grown in the soils. The Ca, Ti, Sr, Al, Zr, and Ba concentrations of soilless grown plants was lower than that of soil-grown plants. Potassium and S concentrations of lettuce plants were higher in HCS, rockwool or cocopeat than for plants grown in LCS. The Mg and Mn concentrations were highest in plants in cocopeat and LCS. Copper concentration of lettuce plants was highest in HCS. Growing media had no effect on Co, As, Pb, W, Hg, Cr, Nb, Cd, In, I, Cs, Ta, Th, Ga, and Ce concentrations. Concentrations of Br, Rb, V, Se was highest in HCS, cocopeat, HCS, LCS and rockwool, respectively. In conclusion, essential element contents and the growth of lettuce plants was better in cocopeat and rockwool medium than the soils. Zirconium, Ba, Ni, Rb, Al and Ti that are not necessary for plants and humans are lower in the lettuce plants growing in rockwool and cocopeat. According to these results, vegetables grown without soil should be considered as an important advantage for human health.