Boron deficiencies in British Columbia: Diagnosis and treatment evaluation

Abstract

Two case-studies are presented, outlining methods of diagnosis and treatment evaluation for boron deficiencies in a Douglas-fir stand in coastal southern British Columbia and a lodgepole-pine stand near Burns Lake, in the interior of the province. Site conditions commonly associated with B deficiency are outlined, and relationships between dormant-season foliar B concentration and growing-season precipitation and moisture stress are suggested. Diagnostic methods used in the study include examination of deficiency symptoms, and foliar-analysis techniques involving the application of critical limits and indices based on the Diagnosis and Recommendation Integrated System. Evaluation of response for corrective fertilizer treatments is based on changes in the frequency and severity of deficiency symptoms and growth responses, measured through a graphical-analysis technique and changes in pre- and post-treatment shoot length between treatments. Boron deficiencies and response to B fertilizers are difficult to confirm. Results of the graphical-analysis technique and examination of the frequency and severity of deficiency symptoms were inconclusive, while changes in shoot length identified a measurable response in the Burns Lake fertilizer trial with lodgepole pine. Deficiencies appear to be acute rather than chronic, and may not occur in untreated control trees for several years after establishment of fertilizer trials. Alternative causes for deficiency symptoms are also common, further complicating diagnosis and evaluation of response to treatment. It is concluded that all future trials should include nitrogen and / or other limiting nutrients with and without B to aid in identification of acute B deficiencies and deficiencies induced by increasing growth.