Effect of neutralizing substances on zinc-contaminated soil on the yield and macronutrient content in yellow lupine (Lupinus luteus L.)

Some trace elements, for example zinc, play both a positive and a negative role in plant life, which requires their content in soil. If soil is excessively contaminated with zinc, an attempt should be made to reduce the negative effect of this element on plants and other living organisms. For this reason, a study was undertaken to determine whether it was possible to alleviate the effect of soil zinc contamination (0, 150, 300 and 600 mg Zn kg-1 of soil) on the yield and macronutrient content of yellow lupine (Lupinus luteus L.). Compost (3%), bentonite (2%) and zeolite (2% relative to soil mass) were used to reduce the effect of soil zinc contamination. Macro- and micronutrients were applied to the soil in the same amounts in all pots: 30 mg N, 30 mg P, 100 mg K, 50 mg Mg, 0.33 mg B, 5 mg Mn and 5 mg Mo per kg soil. Yellow lupine was harvested in the flowering phase and plant material samples were collected for laboratory tests. The induced soil zinc contamination reduced yellow lupine growth and development because a dose of 300 mg Zn kg-1 soil caused plant seedlings to wither. Compost and bentonite reduced the negative influence of soil zinc contamination on yellow lupine yield, especially on aerial parts. The most demonstrable effect of zinc on the macronutrient content of lupine plants was recorded for magnesium and calcium, whose content increased compared to the control in both the aerial parts and roots of yellow lupine. Among the neutralizing substances, the effect of zeolite on the phosphorus, magnesium and calcium content and bentonite on the sodium content in the plants was the most beneficial.