Total heights could not be used as a measure of treatment effects in these studies because trees were sheared each year. However, terminal shoot growth was measured as a possible response to fertilization. As shown in Tables 2 and 6, there were no statistically significant responses to N applications for any of the individual studies. Similar results were noted in earlier studies (Brown, 1976; Brown and Vimmerstedt, 1976) in which terminal shoot growth of trees of six different Christmas tree species (Scotch pine, white pine, Norway spruce, white spruce, Fraser fir, and Douglas-fir) growing on five different sites showed only minimal increases (1 to 11 percent) in shoot growth attributable to N fertilization. However, in those same studies, chemical weed control resulted in major increases in shoot growth of trees (14 to 28 percent) of all species except Scotch pine, with effects being most beneficial to Douglas-fir and Fraser fir growing on well- to excessively well-drained sites.
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Table 2. Effects of Nitrogen Fertilization on Shoot Growth and Needle Lengths of Trees in Studies Established in 1993. | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Fert. Level lbs/ac | Terminal Shoot Growth | Needle Length | ||||||||
| 1993 | 1994 | 1995 | 1996 | 1997 | 1993 | 1994 | 1995 | 1996 | 1997 | |
| ---cm--- | ---mm--- | |||||||||
| Wooster 1: Established 1993 | ||||||||||
| 0 | 27 | 29 | 33 | 31 | 41 | 19 | 17 | 16 | 17 | 18 |
| 100 | 26 | 33 | 30 | 37 | 39 | 21 | 20 | l8 | 19 | 20 |
| 200 | 32 | 36 | 34 | 38 | 38 | 21 | 18 | 20 | 21 | 18 |
| 300 | 26 | 32 | 30 | 36 | 39 | 22 | 20 | 18 | 20 | 19 |
| Avg. | 28 | 32 | 32 | 36 | 39 | 21 | 19 | 18 | 19 | 19 |
| pF1 | 0.63 | 0.54 | 0.42 | 0.09 | 0.67 | 0.46 | 0.27 | 0.25 | 0.13 | 0.44 |
| LSD2 | - | - | - | - | - | - | - | - | - | - |
| Pomerene 1: Established 1993 | ||||||||||
| 0 | 31 | 29 | 41 | 41 | 53 | 22 | 21 | 22 | 23 | 19 |
| 100 | 34 | 39 | 44 | 45 | 53 | 24 | 24 | 23 | 22 | 21 |
| 200 | 35 | 25 | 47 | 48 | 52 | 24 | 24 | 23 | 23 | 19 |
| 300 | 36 | 35 | 48 | 48 | 55 | 24 | 22 | 22 | 22 | 22 |
| Avg. | 34 | 32 | 45 | 46 | 53 | 24 | 23 | 22 | 22 | 20 |
| pF1 | 0.23 | 0.07 | 0.18 | 0.10 | 0.63 | 0.12 | 0.50 | 0.76 | 0.67 | 0.56 |
| LSD2 | - | - | - | - | - | - | - | - | - | - |
| 1 pF: Probability of statistical significance for analysis of variance F test.
2 LSD: Least significant difference at 5% probability level for comparing differences between treatment means. | ||||||||||
In all plantings, terminal shoot growth generally increased in each successive year trees were in plantations (1993 to 1997 or 1996 to 1997), which follows the trend shown in many plantings where growth increases as trees become older and better established in the field. Also, overall growth in the five study areas tended to be best on the better-drained sites (Pomerene 1 and 2) and poorest on the two wettest areas, Pomerene 3 and Wooster 2. This is similar to results (unpublished data) in soil/site studies being carried out by the author with the Canaan Valley seed source of West Virginia balsam fir. Although survival of trees may be very good on many relatively wet sites, shoot growth tends to be less on those areas.