Interprovincial Forest Fertilization Trials 5-and 10-Year Results

Eighty one standard ferilizer trials were established in unmanaged. middle-aged stands of jack pine, black spruce, white spruce, red spruce and balsam fir in Nova Scotia, New Brunswick. Quebec, Ontario, Manitoba. Saskatchewan and Alberta. The 5-year and 10-year total volume responses, based on conventional plot remeasurements, are summarized for installations grouped by Forest Section. A complete report is being published separately. Jack pine stands were most consistently responsive to nitrogen additions; black spruce, red spruce and white spruce and balsam fir were much more variable in response. Spruce budworm defoliation and natural tree mortality resulted in very low or negative net increments for many installations. Where P or K was added with N additional response appeared small. Fertilizer efficiencies of 7 to 35 kg of applied nitrogen per cubic meter of additional response were indicated: recommendations are made for further work on fertilizer response.