A small-plot experiment on microelement contamination was set up in the field on calcareous chernozem soil with loam texture, formed on loess, at the Experimental Station of the Institute for Soil Sciences and Agricultural Chemistry in Nagyhörcsök in spring 1991. The ploughed layer contained around 5% CaCO3 and 3% humus, while the supplies of readily available nutrients were very good for Ca and Mn, satisfactory for Mg and Cu, moderate for N and K, and poor for P and Zn. The groundwater was at a depth of 15 m, and the area had a negative water balance, being prone to drought. Salts of 13 microelements were each applied at four levels (0, 90, 270 and 810 kg·ha-1) in spring 1991, prior to the sowing of maize. The 13×4 = 52 treatments were set up in two replications on a total of 104 plots in a split-plot design. The microelements were applied in the form of AlCl3, As2O3/NaAsO2, BaCl2, CdSO4, K2CrO4, CuSO4, HgCl2, (NH4)6Mo7O24, NiSO4, Pb(NO3)2, Na2SeO3, SrSO4 and ZnSO4. Alfalfa was grown in the 14-18th years of the experiment. Before sowing, in autumn 2003, the plots were fertilized with 400 kg P2O5·ha-1 and 800 kg K2O·ha-1 in the form of superphosphate and potassium chloride. The main conclusions drawn from the results were as follows: - There were no extremely dry years between 2004 and 2008. Partly for this reason, and partly due to the satisfactory nutrient supplies in the soil, the alfalfa could be maintained with satisfactory yields for five years. In general there were four cuts each year between May and September, with the highest hay yields in the first cut. On the control plots a yield of 62.5 t·ha-1 was achieved over the five years. A surplus of around 10 t·ha-1 was recorded in the 90 kg·ha-1 Se treatment, while there was a yield reduction of 8 t·ha-1 on soil excessively polluted with Se. These changes were significant. - The element composition of the hay exhibited a dramatic change on contaminated soil in comparison with the control. Averaged over years and cuts, there was an approximately 2× accumulation of Cu and Zn and a 3× rise in the Sr content. The concentrations of As, Ba, Cd, Cr and Ni rose by at least one order of magnitude and those of Mo and Se by 2-3 orders of magnitude. This enormous increase in the heavy metal contents made the soil unsuitable for feeding purposes. - On uncontaminated soil the alfalfa incorporated a total of 2 t·ha-1 nitrogen into the aboveground crop in the course of 19 cuts over five years, most of which originated from the atmosphere. The average macronutrient uptake (kg·ha-1) over five years was 1546 for Ca, 1232 for K, 200 for P, 200 for Mg, 189 for S and 22 for Na, while the micronutrient uptake was around 7 kg·ha-1 for Fe, 3 kg·ha-1 for Al, Mn and B and 2-3 g·ha-1 for Co. - The maximum element yields over the five years on contaminated soil (per hectare) were 29 kg for Mo, 20 kg for Sr, 19 kg for Se, 2 kg for Ba and Zn, 600 g for Cu, 200 g for Ni and Cd, 150 g for Cr, 130 g for As and 16 g for Pb. - In summary it could be stated that alfalfa could be suitable for the cleansing/remediation of soils moderately contaminated with Mo, Sr or Se under Hungarian conditions. This crop has the advantage of a large aboveground biomass, combined with a deep root system. The latter is important as Se and Mo may pollute the subsoil in the form of selenate/molybdenate and Cr in the form of chromate ions. The hay produced on these areas should not, however, be fed to livestock.
|Translated title of the contribution||Use of alfalfa for the phytoremediation of soil contaminated with microelements|
|Number of pages||19|
|Journal||Agrokemia es Talajtan|
|Publication status||Published - 2014|
ASJC Scopus subject areas
- Agronomy and Crop Science
- Soil Science