Effect of species on the elemental composition of wood ashes and their fertilizer values on agricultural soils

B.Sc. Olalekan Moses Ayodeji, BSc

Master's thesis

Abstract:

Wood ashes have been used as fertilizer on agricultural soil over a long period. So far, the effect of species from different localities on the elemental composition of wood ashes and whether home-made ashes are suitable for agricultural soil as fertilizers is not well-known. The study aimed to analyze the elemental composition of home-made ashes of Betula pendula, Carpinus betulus, Fagus sylvatica, Larix decidua, Picea abies, Pinus sylvestris, Quercus robur, and Tilia cordata from Hlinsko and Mšec localities, Czech Republic, commonly used for heating homes. The elemental composition of the studied wood ashes was determined using portable X-ray fluorescence spectrometry. The wood ashes were characterized by the accumulation of macro (P, K, Ca, and S), micro (Mn, Fe, Zn, and Cu), and other (Al, Si, Rb, Sr, Mo, Zr, Th, and Se) elements, with a significant effect among the species in both sites. The contents of P, K, Ca, and S ranged from (g kg-1) 3.5 to 21.1, 30 to 135, 100 to 300, and 3.7 to 12, respectively, in all the ashes. The contents of Mn, Fe, Zn, and Cu in the ashes of all the species ranged from (in g kg-1) 1 to 32, 0.2 to 4.5, 89 to 2050 mg kg-1, and 50 to 198 mg kg-1. The content of Cu, Sr, and Pb in the ash of Carpinus betulus significantly well correlated with content in the soil from Hlinsko, due to the influence of the soil elemental composition by an abandoned graveyard from past human settlement. The significantly higher content of the elements in the ashes from Hlinsko compared to Mšec resulted from the soil's elemental content and partly from the root absorptive capacity of the species. The ash of Larix decidua in Mšec is unsuitable fertilizer for agricultural soils- characterized by > 100 mg kg-1 Pb. The contents of other risk elements (Ni and As) were below the regulatory limit for Agricultural soils. Hence the studied home-made ashes are suitable to be used as fertilizers. The total content of P, K, Ca, Fe, Mn, Cu, Zn, and Pb in the ashes obtained by pXRF and Aqua regia followed by inductively coupled plasma optical emission spectrometry well correlated. Hence, the pXRF has adequate precision for tracing the elemental signatures. The accumulation of elements in wood ashes of the same species from different localities relates to the genetic makeup of the species, geology, as well as anthropogenic activities of the given location.

Keywords

Betula pendula, Fertilizer, Macro element, Micro element, Risk element, Agricultural soil

Language used: English

Date on which the thesis was submitted / produced: 11. 12. 2020

Thesis defence

• Supervisor: prof. RNDr. Michal Hejcman, Ph.D. Ph.D.

Czech University of Life Sciences Prague

Faculty of Environmental Sciences

Master programme / field:
Engineering Ecology / Nature Conservation