No significant differences were observed among any of the six fertilizer and vegetation control treatments tested. However, the same trend of increasing stem volume with increased radius as seen at Vernonia and Klickitat was observed. This trend was not as pronounced as on the other two sites. Fertilization did not result in significantly greater stem volume between any two similar radius treatments. Conclusion Without adequate vegetation control a positive response to fertilization is unlikely on most reforestation settings in the Pacific Northwest.
Plants require moisture to absorb soil nutrients.
Although not directly measured, the increase in soil moisture resulting from the vegetation control treatments in our study is likely responsible for the growth responses observed in fertilized weeded treatments. Placement of the fertilizer briquettes in the planting hole and the use of a complete fertilizer are also suspected of aiding in the positive fertilizer response measured. Variability was high at each site and, although there were differences in the overall plot means, many individual seedlings failed to respond to fertilization. More research is needed to find which combinations of application technique, weed control and fertilizer formulation will elicit the best response for different tree species on differing sites. Literature Cited Nambiar, E.K.S. and R. Sands.