Table 6 — Average ponderosa pine root growth after 30 days and average seedling heights and survival after 3 years on the 

 Targhee National Forest. Means in each column followed by the same letter or by no letters are not statistically 

 different (a = 0.05) 



Treatment 



Third year root growth 



Roots 

 <0.5 cm 



Roots 

 0.5-2.0 cm 



Roots 

 >2.0 cm 



Total length Avg. length 



Third year 



Height 



Survival 



Vermiculite 

 Vermiculite slurry 

 Aquagel® 

 Not dipped 



No. 



cm 



357 

 540 

 349 

 321 



48 a 

 104 b 

 58 a 

 41 a 



17.8 a 

 33.2 b 

 21.8 ab 

 15.7 a 



62 a 

 130 b 

 85 ab 

 58 a 



2.8 

 3.8 

 3.5 



3.5 



34.6 

 36.5 

 34.6 

 36.4 



Percent 



80.2 

 81.0 

 74.6 

 76.8 



Vermiculite 



Slurry 



Aquagel® Not dipped 



Figure 10 — Average ponderosa pine seedling 

 heights from 480 seedlings after the first three 

 growing seasons on the Boise National Forest 

 (field experiment 2). Seedlings were root 

 dipped in vermiculite, vermiculite slurry, or 

 Aquagel®, or they were not dipped. 



first month after planting than in the greenhouse 

 experiments, growth chamber experiments, and the 

 other field test. Precipitation for April and May 1988 

 was 115 percent of normal at the Idaho City, ID, 

 weather station. Under favorably moist conditions, 

 the vermiculite slurry may be beneficial, perhaps be- 

 cause it provides a greater cation exchange capacity 

 than the surrounding sandy loam soil. 



Root growth varied with species and soil type. Lodge- 

 pole pine grew the most roots on average. However, 

 on granitic or basaltic soils Engelmann spruce root 

 growth was just as good. To further rank species, 

 ponderosa pine had the second-best root growth on 

 the peat-vermiculite-sandy loam soil. Douglas-fir 

 produced the fewest roots on all of the soils. In the 

 second greenhouse experiment the Douglas-fir root 

 growth was less than in the first because the seed- 

 lings were lifted too late in the spring. 



Table 5 shows that in every category of root growth 

 measurement, the undipped seedlings produced as 

 many or more new roots as root-dipped seedlings. 

 However, the situation is not as simple as it may 

 seem. Although the undipped seedlings produced 

 more long roots, figure 1 shows that only ponderosa 

 pine roots produced a difference; there was little dif- 

 ference in the number of Douglas-fir roots. 



The peat-vermiculite-sandy loam soil, with its higher 

 organic matter content, held more water and was more 

 conducive to root growth. The granitic soil with little 

 organic content and large pore spaces held the least 

 water. But the water was not held tightly and most 

 of it was available for uptake by roots. The basaltic 

 soil, with its high clay content, held more water than 

 the granitic soil, but httle water was available to roots 

 when the soil became dry and brick hard. These 



^ 100- 



0) 



o 

 a 



5 90- 



3 

 (/) 

 O) 



(0 



80- 



70- 



Vermiculite 

 Slurry 



1 1 



1 2 



Years 



Figure 11 — Average ponderosa pine seedling 

 survival heights from 480 seedlings after the first 

 three growing seasons on the Boise National For- 

 est (field experiment 2). Seedlings were root 

 dipped in vermiculite, vermiculite slurry, or 

 Aquagel®, or they were not dipped. 



9 



