KENTUCKY CHRISTMAS TREE PRODUCTION WORKBOOK:
Bonnie L. Appleton; Deborah B. Hill
As with any plant material, Christmas
trees need nutrients to increase growth, improve vigor and enhance color.
Some species grown are heavy feeders, some are not; therefore, fertilizer
Major, scheduled fertilization is not
a common Christmas tree cultural practice. Few Kentucky growers fertilize
their trees both because no adequate recommendations currently exist and
because fertilization has not been a standard practice. However, fertilization
may be important and should be considered.
Fertilization should be considered
at 3 times: preplant, at planting time and post-plant. For preplant and
planting time fertilization, a current soil test will be helpful in determining
the type and rate of fertilizer to use. For postplant fertilization more
indirect indicators such as site characteristics, available moisture and
species may be helpful. For example, Scots and Virginia pines will tolerate
dry, unfertile sites; the various spruces and firs will not.
A soil test should be taken (see Cooperative
Extension Publication AGR-16, Taking Soil Test Samples) when land is being
prepared so that if any fertilizers or lime are needed, they can be incorporated
before planting. Incorporation in the fail before a spring planting is
advisable. Remember that Christmas tree needs differ from typical crop
needs. Christmas trees prefer acid soils (pH 5.0-6.5).
Ask to have a soil test run for phosphorus
(P), potassium (K), and pH. If P and K rates are very low or zero, apply
a moderate amount of each (e.g., 40 lb active ingredient/acre P and 160
lb active ingredient/acre K). If the pH is below 5.0, lime to raise it
to between 5.0 and 5.5. If the pH is only mildly acid (6.5), neutral (7.0)
or alkaline (above 7.0), some foliar chlorosis (yellowing) may develop
but it is net economically feasible to add sulfur to lower the pH (except
possibly immediately around each tree using a product like sulfur-coated
urea, SCU). Adding some form of nitrogen (N) may help. Use of leguminous
ground cover also helps.
Preplant fertilizers should be applied
across the entire area to be planted, not just per tree site. Use per acre
rates. Nitrogen fertilizer should not be applied pre-plant due to rapid
losses by leaching and volatilization. Ammonium nitrate and urea also will
burn the new seedlings.
Planting Time Fertilization
At planting time fertilizer may be
applied on a per tree basis. Use slow release materials conveniently packaged
as tablets, spikes, small bags, etc. Place them either in the planting
hole or preferably in the hand planting closing hole. Follow the manufacturer's
Postplant fertilizer should be applied
on a per tree basis, not broadcast on an acre basis. The trees, not grass,
weeds, or surrounding ground cover, should be all that is fed.
If tree growth seems slow or color
is off, fertilization with a high nitrogen (N) fertilizer such as urea
(46-0-0) or ammonium nitrate (33-0-0) may be desirable after the second
year of growth. Here is a chance for growers to experiment to determine
types and rates of fertilizer to use for their species of trees under their
soil and climate conditions (see FOR-32 in this series,
Developing a Demonstration Plot). Whether you want to fertilize before
the growing season for growth or after the growing season for color is
another variable to consider. Some growers have successfully used diammonium
phosphate as a side dressing on trees 4 years old and older.
A fertilizer may supply only one major
nutrient (urea, 46-0-0, supplies 46% nitrogen (N)) or may be complete and
supply all three major nutrients (10-10-10, supplies 10% N, 10% P and 10%
K ). The first number always refers to the percent N, the second, the percent
P and the third, the percent K.The percent equates to a weight basis (ten
lb of a 10-10-10 fertilizer contains 10% each N, P and K or one lb of each--the
other 70% or 7 lb is inert carrier).