The biochar impact on miscanthus and sunflower growth in marginal lands

Abstract

The results of the experiment with biochar as a soil amendment are presented. Two energy crops (Miscanthus × giganteus and Helianthus annuus) were grown in the vegetation containers with two types of marginal lands. Low humus black soil Low humus black was taken in flood plain of Kilchen river. Red-brown clay was taken from the quarry board 15 yeas ago to create reclaimed mine land in site near “Blagodatna” coal mining tailing. It was defined that the biochar addition intensifies growth processes from 7‒30% (Helianthus) to 20‒88 % (Miscanthus). For Miscanthus, the effect was more pronounced on black soil, and for Helianthus on red-brown clay. Due to the biochar application, the plant capacity to take up heavy metals by above-ground organs decreased. As a result, the heavy metal content in leaves and stems has reduced by an average of 10‒25%. However, because of the gain in biomass productivity, the uptake level of some heavy metals has increased. Especially, this was characteristic of the Miscanthus leaf biomass. So, the uptake of heavy metals by leaves increased from 28.1% (Pb) to 62.9% (Fe) on the black soil, and from 20.3% (Cu) to 46.6% (Zn) on the red-brown clay. The addition of biochar had a slight effect on thermolysis passing of Miscanthus and Helianthus biomass. So, in Miscanthus, duration of the process has grown shorter. The rate of thermal degradation in the leaf biomass was greater, which is especially noticeable in the region of hemicelluloses destruction. In the stem biomass a pronounced increase in the thermolysis rate was noted in the region of volatile components evaporation (on the black soil) and during the cellulose decomposition. Besides, under the impact of biochar, biomass combustion was more complete (by 5.1% on the red-brown clay and by 30% on the black soil). In leaf biomass of Helianthus, the onset of thermolysis has shifted toward higher temperatures. In addition, the magnitude of the thermal effect was greater at almost all stages of decomposition. In stem biomass, thermal effects also increased, but only slightly. Under the influence of biochar, the first stage of decomposition was faster. In biomass taken from red-brown clay, the rate of hemicellulose degradation also increased. In biomass taken from black soil, biochar application contributed to more intensive decomposition of lignin. After combustion, the share of residual mass in stem of plants grown on black soil with the biochar addition increased by 30%. The opposite effect was observed on red-brown clay: the share of residual mass decreased by 49%. Besides, the thermal stability of stem biomass grown on the substrates using biochar lessened by 8‒16%