Thick slurries can prevent oxygen from penetrating 

 to the root system in heavy soils. 



Most of our experiments dealt with dry soil condi- 

 tions, very similar to typical planting sites in the 

 Intermountain West. Under these conditions, root- 

 dip treatments did not increase root growth, shoot 

 growth, or survived of lodgepole pine, ponderosa pine, 

 Douglas-fir, or Engelmann spruce. In most cases 

 these root dips were not detrimental, but for potted 

 trees, the thicker the vermiculite slurry, the poorer 

 the seedling root growth. This may translate into 

 reduced survival and growth under field conditions. 



Other work has shown that root dips reduce harm- 

 ful effects of seedling root exposure prior to planting 

 (Dierauf and Marler 1969, 1971; Owston and Stein 

 1972; Tabor and Davey 1966; Williston 1967). Even 

 so, when nursery stock is protected during lifting, 

 handling, storage, and planting, there is no reason 

 to bother with root dipping. It is more important to 

 start with vigorous planting stock, protect the seed- 

 lings from exposure, and maintain their vigor until 

 they are properly planted. 



Summary 



The root dips did not improve seedling root or 

 shoot growth under dry conditions. In potted seed- 

 ling experiments the undipped seedlings produced as 

 many or more roots than the root-dipped seedlings. 

 The thicker the vermiculite slurry treatment, the 

 less roots grew. 



Seedling growth and survival were not significantly 

 affected by root-dip treatment. Overall, the root-dip 

 treatments did not change plant water potential or 

 the seedlings' ability to form mycorrhizal associations. 



Lodgepole pine seedlings grew more new roots than 

 seedlings of other species. Lodgepole pine performed 

 best on the peat-vermiculite-sandy loam soil. Engel- 

 mann spruce produced as mziny new roots as lodgepole 

 on the two forest soils and grew better than the other 

 species on granitic soil. Ponderosa pine also grew well 

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

 root growth was the poorest of all species on all soils. 



The peat-vermiculite-sandy loam was the soil most 

 conducive to seedling root growth for all species ex- 

 cept Engelmann spruce. More mycorrhizal root tips 

 were produced on the granitic soil; the least were pro- 

 duced on the basaltic soil. Seedlings on the basaltic 

 soils also showed the lowest plant water potential. 



Root dipping has been used in the Intermountain 

 West, where soils and planting sites often become very 

 dry during summer. One purpose of root dips is to 

 protect seedlings against exposure or anything else 

 that could go wrong before planting. Instead, man- 

 agers should make every effort to prevent seedlings 



from being exposed to sun and wind, to maintain the 

 vigor of nursery stock before planting, and to properly 

 plant each seedling. The second purpose of root dips 

 is to protect seedlings against the normally dry sum- 

 mer climate that sometimes turns droughty. It ap- 

 pears that even under these conditions the root dip 

 treatments do not help the seedlings and in some 

 cases may harm them. 



References 



Dahlgreen, Allen K. 1976. Care of forest tree seed- 

 lings from nursery to planting hole. In: Proceed- 

 ings: tree planting in the Inland Northwest; 1976 

 February 17-19; Pullman, WA. Ogden, UT: U.S. 

 Department of Agriculture, Forest Service, Inter- 

 mountain Region: 204-238. 



Dierauf, T. A.; Marler, R. L. 1969. Clay dipped vs. 

 bare rooted seedling survival. Tree Planters' Notes. 

 20(2): 5-8. 



Dierauf, T. A.; Marler, R. L. 1971. Effect of exposure, 

 clay treatment, and storage on survived and growth 

 of loblolly pine seedlings. Occas. Rep. 34. Virginia 

 Division of Forestry: 1-10. 



Echols, R. J.; EzeU, A. W.; Meier, C. E.; McKinley, C. R. 

 1990. Dry site survival of bareroot and container 

 seedlings of southern pines from different genetic 

 sources given root dip and ectomycorrhizal treat- 

 ments. Tree Planters' Notes. 41(2): 13-21. 



Johnson, M. S. 1984. The effects of gel-forming poly- 

 acrylamides on moisture storage in sandy soils. 

 Journal of the Sciences of Food and Agriculture. 

 35: 1196-1200. 



Kroll, James C; Deauman, William C; Foster, 

 C. Darwin; Kulhavey, David L.; Tracey, David. 1985. 

 Survival of pines on droughty soils: two year results. 

 In: Proceedings: southern silvicultural reseeirch 

 conference; 1984 November 7-8; Atlanta, GA. At- 

 lanta, GA: U.S. Department of Agriculture, Forest 

 Service, Southern Region: 128-130. 



Magnussen, Steen. 1986. Effects of root-coating with 

 the polymer waterlock on survival and growth of 

 drought-stressed bareroot seedlings of white spruce 

 (Picea glauca (Moench) Voss) and red pine (Pinus 

 resinosa Ait.). Tree Planters' Notes. 37(1): 15-17. 



MuUin, R. E.; Bunting, W. R. 1979. Another look at 

 clay dipping of bare-root nursery stock. Forestry 

 Chronicle. 55(5): 183-188. 



Mullin, R. E.; Hutchison, R. E. 1977. Agricol, clay and 

 water dipping tests with jack pine and black spruce 

 nursery stock. Forest Research Notes. 10: 1-3. 



Owston, Peyton W.; Stein, William I. 1972. Coating 

 materials protect Douglas-fir euid noble-fir seedlings 

 against drying conditions. Tree Planters' Notes. 

 23(3): 21-23. 



11 



