project V
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project V: application of Fly-Ash to improve the base status of soils and vegetation in acid soils in central Ontario

There is increasing evidence that base cation reserves in forest soils are being depleted due to a combination of acid deposition and tree harvesting (Adams et al. 2000; Federer et al. 1989; Houle et al. 1997; Lawrence et al. 1997). Base cations, in particular Ca and Mg, may become limiting to tree growth, or predispose trees to other stresses such as insects and drought (Demchik and Sharpe 2000; Horsley et al. 2000). In central Ontario, poor tree growth and die-back have been associated with low Ca levels, low soil pH and high Al concentrations in soil (McLaughlin et al. 2000; Watmough 2001). Large losses of exchangeable Ca have been recorded over a 17-year period at two watersheds near Dorset in central Ontario (Watmough and Dillon 2001). At one of these watersheds, there has been no increase in forest growth during the corresponding time period and so losses of Ca from soil can by attributed solely to acid deposition. The second watershed is dominated by maple and has a much greater exchangeable base cation pool. Base cation losses at this site have been greater because of substantial uptake by trees and greater losses through leaching. Continued losses of base cations from soil may eventually lead to nutrient deficiencies in trees (Bernier and Brazeau 1988) and increased Al mobilization, which is also potentially toxic to trees and aquatic life.

A number of studies have found that applying fertilizers to surface soils improves the base status of soils and improves the nutrient content, growth and health of trees (Cote et al. 1993; Fyles et al. 1994; Moore et al. 2000; Wilmot et al. 1996). In fact, in the late 1980s fertilization was adopted as a primary means of controlling sugar maple die-back in southern Quebec (Hendershot and Courchesne 1994). A number of different fertilizer treatments have been used with varying degrees of success (Cote et al. 1993).

Fly ash (FA) is a byproduct of coal combustion and is composed of particulate matter collected from the flue gas stream. Numerous studies demonstrated that FA can have significant beneficial effects in addressing certain problems in soil quality. The application of FA can also improve the physical properties of soil and may increase the water holding capacity of soil. However, Adriano and Weber (2001) also stated that there are potentially detrimental effects of FA application including the presence of boron and the long-term availability of trace metals (including Mo, Se and As). The use of FA as a fertilizer has been used primarily on agricultural soils, although the beneficial effects of certain types of FA appear suited to alleviating nutrient deficiencies on acid forest soils, provided that there are no detrimental effects of FA application. This study aims to assess the impact of FA application on soil chemistry and tree health and chemistry in central Ontario.

Two different FA’s will each be applied to sugar maple trees at 3-dosages; in addition, a control treatment will be included in the study. Soil and foliar chemistry (base cations; trace metals; Al; N and S) will be assessed prior to application and after application. The plots will be re-sampled in mid-August on a yearly basis to assess the long-term effects of FA application. In addition, soil cores, including the litter layer, will be collected in early summer 2002 from the field application site to allow more detailed soil analyses. FA will be applied at dosages equivalent to those used in the field trials. Water will be applied at pre-determined levels that are representative of actual conditions and soil leachate collected from the cores will be collected and analyzed to assess the mobility of base cations, and trace metals over time.