Photosynthetic and Growth Responses of Two Broad-Leaf Tree Species to Irrigation with Municipal Landfill Leachate
- S. C. Shrive,
- R. A. McBride * and
- A. M. Gordon
A study was undertaken to investigate leaf photosynthesis and stem growth responses of saplings of two broad-leaf tree species to irrigation with municipal solid waste (MSW) leachate in a northern temperate climate at Ontario, Canada. The objective was to quantify plant stresses or changes in plant productivity that could be attributed to this low technology option for the treatment and disposal of groundwater contaminated by municipal refuse. Red maple (Acer rubrum L.) and hybrid poplar [Populus spp. nigra × maximowiczii (NM6)] were subjected to two consecutive seasons of leachate irrigation in a three factor, RCBD split-plot field experiment. The three factors were irrigant type (MSW leachate, water), mode of application (spray, surface trickle, subsurface irrigation), and rate of application (3.5, 7.0, and 14.0 mm d−1). The main treatment plots in each of three blocks were split into subplots planted to different tree species. In the second irrigation season, the mean seasonal photosynthesis rates increased for irrigated saplings of both species relative to rain-fed control saplings, irrespective of irrigant type. Mean seasonal photosynthesis rates for red maple increased with irrigant application rate, but were unaffected by irrigant type. Incremental stem diameter and height growth for this species were largely unaffected by the experimental treatments. Mean seasonal photosynthesis rates for hybrid poplar were unaffected by either irrigant type or application rate, but stem growth did increase significantly with leachate irrigation. The mode of irrigant application was not a significant factor in explaining plant response for either species. Direct exposure of leaves to potentially phytotoxic compounds in MSW leachate (volatile organics, and inorganics including metals) by spraying did not induce phytotoxic symptoms in the saplings. Irrigation of a MSW leachate of relatively high ionic strength can be carried out successfully on clay soils under Ontario climatic conditions without causing significant adverse effects on saplings of these tree species. Treatment and disposal of MSW leachates in tree plantations may offer a low technology, low cost option to municipalities.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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