The effect of 0, 30, 90 and 270 kg ha-1 microelement load on garden sorrel was examined on calcareous sandy soil in the Danube-Tisza mid-region. The microelement salts were applied in one turn in the form of Cr2(SO4)3, K2Cr2O7, CuSO4, Pb(NO3)2, Na2SeO3, ZnSO4 in the spring of 1995. The 6 elements × 4 loads = 24 treatments × 3 replications resulted in 72 plots, each 7 × 5 = 35 m2 in size. The production site had bad water management, it was weakly supplied with NPK and the soil is drought-sensitive, which is typical of sandy soils. The ploughed layer contains 0.7–1.0% humus, 2–3% CaCO3 and the soil water level is at 5–10 m. 100 kg N ha-1, 100 kg P2O5 ha-1 and 100 kg K2O ha-1 basic fertilisers were used each year in the whole trial. Main results:

1. Altogether, there was 152 mm rainfall during the 3-month long growing season of garden sorrel. The green leaf yield remained moderate on unpolluted control soil, fluctuating between 13–17 t ha-1 with 11-12% air-dry matter content.

2. Of the elements applied 5 years ago, less than 1% of Cr, 2% of Se, 20% of Zn, 38% of Pb and 44% of Cu were found in accumulated form in the ploughed layer in NH4-acetate+EDTA-soluble form. It is assumed that the majority of the Cr(VI) and Se content was leached into deeper layers, while Zn, Pb and Cu could have transformed into other forms in the soil.

3. Toxicity was observed in the case of Se content above 1 mg kg-1 and Zn content above 9 mg kg-1. The yield of garden sorrel decreased to one fifth on the soil which contains 2 mg kg-1 Se, while it decreased to its half on the soil that contains 19 mg kg-1 Zn.

4. The highest Cr and Pb concentration in the leaf was only 4–5 mg kg-1, while other values were 8 mg kg-1 Cu and 38 mg kg-1 Zn on polluted soil, showing moderate accumulation. However, the amount of Se increased to 446 times its concentration in the control plot, showing hyperaccumulation. The highest value of element uptake was shown by 6–8 g ha-1 Cr and Pb, 13 g ha-1 Cu, 38 g ha-1 Zn and 211 g ha-1 Se. The leaf of garden sorrel grown on polluted soil became unsuitable for human consumption due to the accumulation observed in the Pb and Se treatments. However, the moderate Cr and Cu accumulation could even improve the biological value of yield.

5. The specific element content of 10 t ha-1 fresh garden sorrel yield was 22 kg N, 18 kg P2O5, 53 kg K2O, 25 kg CaO, 20 kg MgO and 3 kg S on the control plot. The small yield was accompanied with elevated element contents in dry years. We do not recommend to consider these values when calculating the element demand of plants during consultancy.

Keywords: garden sorrel, microelement-load, calcareous sandy soil, toxicity, field trial