EFFECT OF MICROELEMENTS ON ALFALFA ON A SANDY SOIL
The effect of 0, 30, 90 and 270 kg·ha-1 rates of microelements on alfalfa was examined on a calcareous sandy soil in 2004 - 2008 in Őrbottyán, Hungary. The salts of the microelements were applied on a single occasion at the start of the experiment in spring 1995 in the form of Cr2(SO4)3, K2Cr2O7, CuSO4, Pb(NO3)2, Na2SeO3 and ZnSO4. The 24 treatments (6 elements×4 application rates) in 3 replications gave a total of 72 plots. The location was prone to drought and was poorly supplied with NPK macronutrients. The ploughed layer contained 0.7–1.0% humus and 2–3% CaCO3, and the groundwater was located at a depth of 5–10 m. The whole experiment was given 100 kg·ha-1 each of N, P2O5 and K2O active ingredients as basal fertilizer each year.The favourable precipitation contributed to the advantageous development and yield of alfalfa during the 5 years period. Pb and Cu loads remained in the ploughed layer. The 0.2-0.4 mg∙kg-1 Pb-content of the control alfalfa hay increased to 0.5-1.4 mg∙kg-1 on the treated soil on average. Cu concentration rose from 5-7 mg∙kg-1 to 9-10 mg∙kg-1 due to the maximal Cu load. Se showed an extreme 3-fold accumulation in hay, i.e. from under 1 mg∙kg-1 detection limit to 200-400 mg∙kg-1. The hay became unsuitable for feeding. However alfalfa can be utilized in phytoremediation. During the 5 years the total yield of 45.5 t∙ha-1 alfalfa hay contained 6-12 kg∙ha-1 Se. In 2006 after the 12th year of the experiment the leaching zone of Cr(VI) exceeded 3 meters, and that of Se exceeded 4 meters in 270 kg∙ha-1 treatments. Vertical movement could not be verified in the case of Cr(III), Pb, Zn, Cu.
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