Monitoring the changes in total contents of manganese, copper and zinc in soils from long-term stationary experiments

The objective of the long-term stationary experiment was to discover the effect of the year, production region, soil kind and soil type on total contents of micronutrients (Mn, Cu and Zn) in the soils. In the years 1982 to 1998 the soil was sampled in 7 selected localities. Analyses and extractions determining the total content of metals were carried out by means of mineralization in the HF-H2O2-HNO3 open system. The AAS method was used to determine the contents of the micronutrients. The content of manganese ranged between 296.2 and 978.6; copper between 6.1 and 25.7 and zinc between 29.5 and 99.8 mg·kg–1 of soil. During the experimental period 1982-1998 the total content of Mn and Zn decreased (by 7.9 and 3.6%, respectively), but was not statistically significant (p < 0.05). During the 15 years of the experiment the total amount of copper in the soil increased by 7.0%. In comparison with the potato growing region the contents of all the micronutrients in the sugar-beet growing region were higher. The highest and statistically highly significant difference (p < 0.001) was that of copper (45.6% increase). In terms of the soil kind the lowest contents of Mn and Cu were monitored on light soil. The total content of zinc on light soil and medium-heavy soil was comparable. With an increasing proportion of clay particles in the soil the contents of the micronutrients increased significantly (p < 0.001). In comparison with light soil, in heavy soil the contents of the metals increased; Mn by 38.9; Cu by 48.2 and Zn by 19.4%. The levels of Cu and Zn were also affected by the soil type. The contents of these micronutrients were statistically (p < 0.001) the highest in chernozem (24.6 and 71.1 mg·kg–1 of soil, respectively). The content of Mn was the highest in brown soil (714.3 mg·kg–1 of soil). Graded rates of fertilisers did not have a significant (p < 0.05) effect on the total contents of metals. The differences were more marked in the treatment where liming was not carried out; here we monitored the greatest decrease in the contents of Mn, Cu and Zn, ie by 7.3, 23.8 and 9.4%, respectively, compared with the control.