Content of organic carbon, total nitrogen and available forms of macronutrients in soil contaminated with cobalt

Cobalt plays a special role in living organisms. However, it becomes harmful to their growth after its concentration exceeds an acceptable level. The aim of this study was to determine the effect of increasing levels of cobalt in soil (0, 20, 40, 80, 160, 320 mg kg-1 d.m. of soil) following the application of neutralising substances on the content of Corg, total-N and available forms of P, K and Mg in soil. The neutralising substances applied in the experiment included manure, loam, charcoal, zeolite at 2% of the soil weight, and calcium oxide at a dose corresponding to one unit of HAC. The same levels of materials were also applied to the soil. Spring barley was the main crop, and white mustard was the successive crop. Applying both increasing levels of cobalt and neutralising substances to soil had a significant effect on the content of Corg, the macronutrients under study and the C:N ratio in soil. Increasing levels of cobalt in the series with no neutralising substances increased the content of Corg and available K, widened the C:N ratio and reduced the content of total-N in soil. Among the neutralising substances under study, charcoal increased the content of Corg and widened the C:N ratio the most and, in the case of total-N, the greatest and negative effect was caused by calcium oxide. The addition of manure to soil increased the content of available P, K and Mg the most. Among the other neutralising substances, zeolite had the greatest effect, as it reduced the content of Corg, available P, K and Mg and reduced the C:N ratio in soil. A similar effect of charcoal on the content of total-N and P and of calcium oxide on the content of K was observed.