Calorific Value of Zea mays Biomass Derived from Soil Contaminated with Chromium (VI) Disrupting the Soil’s Biochemical Properties

Abstract

One of the major challenges faced by contemporary agriculture is how to achieve better yields of crops and, consequently, higher biomass, even in unfavorable environmental conditions. This challenge corresponds to the assumptions of sustainable development, wherein it is envisaged that plant biomass should be used on a large scale for heat generation or conversion of biofuels. Keeping pace with observed trends, the following study was conducted in order to determine the effect of Cr(VI) on the net calorific value of Zea mays, to assess the impact of this element on soil enzymatic activity, and to identify the effectiveness of compost and humic acids in alleviating possible negative effects of Cr(VI) toxicity. These aims were pursued by setting up a pot experiment, in which soil either uncontaminated or contaminated with increasing doses of Cr(VI) of 0, 15, 30, 45, and 60 mg Cr kg−1 d.m. was submitted to biostimulation with compost and the preparation HumiAgra, a source of humic acids, and cropped with Zea mays. The plant height, yield, and net calorific value of the aerial parts of maize, as well as its root yield, were determined. Additionally, the activity of seven soil enzymes and the values of the impact indices of compost and HumiAgra relative to the analyzed parameters were determined. It was found that Cr(VI) decreased the amount of energy obtained from the plants by decreasing maize biomass, and additionally by distorting the biochemical balance of the soil. Dehydrogenases, urease, and arylsulfatase proved to be particularly sensitive to this element. It was demonstrated that HumiAgra was more effective than compost in mollifying the adverse effects of Cr(VI) on the activity of soil enzymes and, consequently, on the biomass of Zea mays.