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Proceedings of Past Forest Nursery Association Meetings:

Effects of Contrasting Fertilizer Regimes on Greenhouse Growth and Outplant Performance of Containerized Jack Pine
G.S. Henderson, W. Smith, B. Nicks
1994: Moscow, ID
Jack pine seedlings were raised in Jiffy #165 containers at nine fertilizer regimes to assess whether pre-plant characteristics could be related to subsequent outplant performance. Seedlings received a top dressing of between 0 and 49 mg N per seedling over a twelve week greenhouse growing period in the summer of 1989. At rotation end, only the two lowest fertilizer regimes, representing less than 4.1 mg N per seedling,displayed significantly decreased height, diameter, and total dry weight. Toxic growth response to high N levels was not detected. Three years after planting on a sandy outwash site, seedling stem volume was significantly higher in fertilizer treatments which delivered more than 11 mg N per seedling. Stem volume increase was 20-58 % more than the conventional regime of 8.1 mg N per seedling. Field growth was positively related (R2= 0.82) with increasing shoot to root ratios of seedlings at the greenhouse; coeffcient of determination was much weaker with all other preplant seedling parameters. Nitrogen content in seedlings also showed a high positive coefficient of determination (R 2= 0.71) with field performance. The greatest plantation response was evident in seedlings that contained 31% more nitrogen than conventional seedlings prior to planting. It is postulated that N content is the more useful predictor of seedling outplant performance as it is a robust measure of pre-plant seedling size and nutrient status. Our results indicate that jack pine seedlings be reared under regimes which deliver more than 11 mg N per seedling to induce luxury consumption of fertilizer in tissue, which effectively `loads' seedlings with nitrogen at greenhouse rotation end and stimulates enhanced growth after planting. Additionally,the build up of a nutrient reserve by high fertilizer regimes prior to planting offers a cost-efficient and specialized advantage to jack pine seedlings over site vegetation competing for early establishment in sandy plantations. The utility of high N fertilizer application in enhancing early field performance of jack pine along with the facility of implementing such luxury consumption fertilizer regimes in the greenhouse suggests that N content is a beneficial complementary parameter for assessing seedling quality in containerised stock programmes.
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