Effects of Non-Industrial Wood Ash (NIWA) Applications on Soil Chemistry and Sugar Maple (Acer saccharum, Marsh.) Seedling Growth in an Acidic Sugar Bush in Central Ontario

Holly D Deighton,Shaun A Watmough

doi:10.3390/f11060693

Abstract

Research Highlights: In central Ontario, large quantities of non-industrial wood ash (NIWA) are generated and could be used as a forest soil amendment to counteract soil acidification and base cation depletion caused by decades of acid deposition. Background and Objectives: The properties and biogeochemical responses of NIWA have not been thoroughly explored, and field experiments must be conducted before NIWA can be regulated as a forest soil amendment in Ontario. Materials and Methods: In this study, soil chemistry and sugar maple (Acer saccharum, Marsh.) seedling growth and chemistry were measured in an acidic sugar bush over twelve months following a NIWA field experiment. Plots (2 m by 2 m) were established with sugar maple, white pine (Pinus strobus L.), and yellow birch (Betula alleghaniensis Britt.) NIWA treatments applied at rates of 6 Mg ha−1 along with untreated control plots. Results: Ash chemistry varied significantly among species and yellow birch ash generally had much higher metal concentrations compared with other species. Following ash application, significant increases in soil pH and calcium and magnesium concentrations were observed, however the level of response varied by treatment. Foliar concentrations of base cations in sugar maple seedlings significantly increased in ash treatments and there was no significant treatment effect on foliar metal concentrations or seedling growth. In roots and shoots, concentrations of several metals (manganese, aluminum, iron, boron, arsenic, cadmium, zinc, copper, lead, chromium, and nickel) increased after ash application, however response was most pronounced in yellow birch ash. Conclusions: These results suggest that application of NIWA can counteract the lasting effects of acid rain by increasing soil pH and base cation concentrations, as well as increasing sugar maple seedling foliar nutrient concentrations, but ashes from species with high metal contents may also increase metal availability to vegetation, at least in the short-term.

Highlights

Acid rain has resulted in surface water acidification [1,2] and accelerated nutrient leaching from forest soils [3,4] across North America
The chemical composition of ash from the three tree species used in this study is generally representative of a broad range of tree species found in eastern North America
Metal concentrations in the three non-industrial wood ash (NIWA) were lower than recommended limits for unrestricted land application in Ontario with the exception of Cu, Cd, and Zn concentrations, but these metals were under limits for restricted land use

Summary

Introduction

Acid rain has resulted in surface water acidification [1,2] and accelerated nutrient leaching from forest soils [3,4] across North America. While some studies have suggested that signs of soil recovery from acidification are emerging [9], full chemical recovery will be slow, perhaps taking centuries because of low base cation weathering rates [10]. Increased forest harvest intensity may slow recovery by removing additional base cations from the Forests 2020, 11, 693; doi:10.3390/f11060693 www.mdpi.com/journal/forests. Forests 2020, 11, 693 site and increasing soil acidity [11,12]. Chemical recovery of soils may be accelerated with additions of lime [13,14] or wood ash [15]. Increased production of wood ash from biomass combustion, as well as high costs of landfilling [16], has sparked interest in using wood ash as a forest soil amendment [17]

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Conclusion