Effects of fertilization at the time of planting on field performance of 1+1 Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings

Graduation date: 2002To study the combined effects of seedling quality and fertilization at the time of planting, three experiments were established in western Oregon during the winter of 2000. The first experiment investigated the effect of preplanting rootvolume and fertilization rate on the field performance of 1+1 Douglas-fir seedlings during two growing seasons. Results from this experiment showed that preplanting root volume is a good predictor of field performance. Seedlings with larger preplanting root volume survived and grew more than seedlings with smaller preplanting root volume. Fertilization at the time of planting slightly reduced survival, stimulated shoot and diameter growth during the first growing season, and reduced all parameters during the second growing season. The second experiment examined the effects of fertilizer placement in combination with fertilization rate on the performance of 1+1 Douglas-fir seedlings during two growing seasons. Results of this experiment showed a significant interaction for seedling survival between fertilizer placement and fertilization rate. Seedlings fertilized on the roots at the highest rate had the lowest survival (50%), while survival of all other treatments was above 70%. Fertilizer placement and fertilization rate did not affect seedling growth during the first growing season. However, during the second growing season, seedlings fertilized on the surface and those dibbled fertilized grew the most in height and diameter. Fertilization rate reduced seedling height growth but did not affect stem diameter growth. A third experiment monitored nutrient release patterns of similar controlled release fertilizers with different fertilizer release rates applied on the field over a 14-month period. Fertilizers with shorter release periods released more fertilizer by weight than fertilizers with longer release periods. However, none of the fertilizers studied released their nutrients in the time specified by the manufacturer. It is suggested that low soil temperatures and low soil moisture may have delayed the release periods of the fertilizers