Reprinted from SOIL SCIENCE SOCIETY OF AMERICA PROCEEDINGS Vol. 30, No. 6, November-December 19661 pages 796-799 G77 South Segoe Road, Madison, Wisconsin 53711 USA Purchased by the U. S. Forest Service, for official use. Growth and Nutrient.Uptake of Irrigated Young Ponderosa Pine After Fertilizer Treatments•
RoBERT F. TARRANT AND RoY R. SrLEN2
ABSTRACT
pine seedlings grown for 1 year responded by increased top
weight to N fertilizer alone and more so to combinations of N
and P and N and S.
In the current study, N and P fertilizers and supplemental
water were applied to the soil beneath young ponderosa pine
trees planted in a windbreak near a source of irrigation water.
Objectives were twofold: (i) to determine effect of relatively
heavy fertilizer treatments and irrigation on flower and cone
production; (ii) to study growth and nutrient uptake after
applying fertilizer to soil under conditions of substantial relief
from moisture stress and competition.
Interest in flower and cone production "ras aroused by
observations of precocious cone bearing in 6-year-old planted
trees. Flo\vering and cone production have been stimulated
in a number of tree species by various cultural treatments,
including irrigation and chemical fertilization (6, 12, 17). On
the other hand, cultivating, \vatering, and fertilizing young
western white pine did not substantially increase fl.o\vering or
tree growth (2).
Cone production in this study, even on fertilized plots, was.
too lo\v to yield definite information. Even though the few
cones produced were generally associated with N--fertilizer
treatments, their distribution could have occurred by chance.
The growth and nutrient uptake phase of the study was
carried on over a 6-year period.
Ammonium nitrate and treble superphosphate were applied to
irrigated, 7-year old ponderosa pine
(Pinus ponderosa
Laws.)
in a wind break planted on Deschutes sandy loam in central
Oregon. Nitrogen was supplied at levels of 0, 200, and 400 lbI
acre and Pat 0, 100, and 200 lb/acre in a factorial experiment.
Fertilizer
treatments
application.
were
repeated
two
years after initial
Over a 6-year period after first fertilizer treatment, tree
growth was stimulated in relation to amount of N applied singly.
When N and P were applied together in various combinations,
growth was in some cases stimulated and in other cases reduced,
according to the combination of the two elements. Foliage N
concentration was not affected significantly by any treatment,
but when P was applied at the 100-lb rate, addition of N treat­
ments caused a linear increase in foliage N concentration. With P
at -200 lb, addition of N caused a linear decrease in foliage N
concentration.
At the conclusion of the study, N content of soils receiving the
heaviest N fertilizer application was only about 11 % more than
that of the controls. However, under heaviest P treatments soil
P was more than five times that of unfertilized soils.
PINE (Pinus ponderosa Laws.) is the most
widely distributed species of its genus in North America.
Because it occurs mainly in areas of comparatively low
precipitation in the V\Testern USA, its growth is often Slow
compared with that of many other commercial tree species.
Thus, ponderosa pine- appears to be· a potentially rewarding
tree with \Vhich to attempt stimulation of growth and perhaps
cone, production, with chemical fertilizer.
Many references are available on studies of the effect of
chemical fertilizer on growth and nutrient uptake of various
species of Pinus, but only a few are concerned with ponderosa
pine. In one of these, nutrient uptake of ponderosa pine
seedlings growing in Pacific Northwest tree nurseries "'as
highest for N, intermediate for K, and lowest for P (19).
When irrigation and N fertilizer treatments were applied to
90-year-old ponderosa pine, supplemental water had more
effect in increasing diameter growth than N (13). Effects of
N, P, and K fertilizer were studied in a 12-year-old plantation
of ponderosa pine with an understory of naturally propagated
western white pine (Pinus monticola Dougl.) and grand fir
[Abies grandis (Doug!.) Lindi.] (10). Although understory
trees responded to fertilizer with increased_ height- growth1
needle length, and foliage nutrient concentration, overstory
ponderosa pine showed only slight gro"\'i'th increase and no
change in foliage nutrients. In another study (20), ponderosa
ONDJ<JROSA
P
STUDY PROCEDURES
The study was begun in the spring of 1957 at tho US Forest
Service tree nursery near Bend, Oreg., where 176 ponderosa pine
trees were growing 6 feet apart in the outer row of a windbreak.
All trees had been raised from seed of a single but unknown
Northwest source and were outplanted when 2 years old. 'Vhen
the study began, the trees were 7 years old, averaged 5.6 feet in
height and 0.90 inch dbh. (diameter at breast height), and were
free from major competition for light, water, and nutrients.
The Bend Nrnsery is situated on a Brown soil of the Deschutes
series, developed principally from windborne pumice sand derived
from volcanic material erupted south of Bend. The soil has a
loamy sand surface texture, is 18-24 inches deep, and overlies a
fractured basalt substratum. Before the tree nursery was estab­
lished in 19461 the soil had been cultivated for a number of years.
Topography is gentle with slope not exceeding 3 %. Native
plant cover before cultivation included western juniper (Juniperus
occidentalis Hook.), sagebrush (Artemisia tridentata Nutt.), and
rabbitbrush (Chrysothamnus spp.). The po'nderosa pine timber
type extends to \Vithin about 2 miles of the nursery site and is
apparently limited only by low rainfall (about 10 inches) at this
northern edge of an extensive commercial forest area.
The row of 176 trees was divided into 3 blocks, \vithin each of
which 9 plots of 3 trees each were randomly selected. An 18-foot
buffer strip _separated plo.ts.
Before fertilizer was applied, a deep-running colter was drawn
between the pine rO\V and interior trees in the windbreak to
reduce root competition from adjacent trees. On the outer side
of the pine row, open ground \Vas disced and periodically hand­
'
hoed to eliminate grass and weeds.
All -9 combinations of 0, 200, and 400 lb/acre of N (as
ammonium nitrate) and 0, 100, and 200 lb/acre of P (as treble
i Contribution from Pacific Northwest Forest and Range
Experiment Station, Forest S_ervice, USDA, Portland, Oreg.
Presented before Div_. S-7, Soil Science Society of America
Nov. 18, 1963 at Denver, Colo. Received June 17, 1964. Approved
July 7, 1966.
superphosphate) were assigned randomly in each block and the
broadcast fertilizer treatment was repeated in 1959 (per-acre
fertilizer rates hereafter referred to as N-200, N-400, P-100, or
ro P-200 ). During each year of the study, deep coltering between
Principal Soil Scientist and Principal Plant Geneticist, re­
spectively, Forestry Sciences Laboratory, Pacific Northwest
Forest and Range Exp. Sta. Corvallis, Oreg.
2
796
797
TARRANT AND SILEN: GROWTH AND NUTRIENT UPTAKE OF PONDEROSA PINE
Table I-Average yearly height and diameter growth-effect of
three levels of N fertilizer across each of three levels
of P fertilizer.
Phosphorus,
lb/acre
0
200
Height Growth,
0
100
200
Probabilityt
Nitrogen, lb/acre
1.51
1.42
1.67
1.60
1.74
1.49
400
PL
0.05*
.47
.06
Location
Average annual growth
Age period
of measurement*
Height
Diameter
Years
Feet
Inches
PQ feet
1.79
1.53
1.39
Table 2-Average annual growth of irrigated ponderosa pines
co pared with that of unirrigated trees near Bend, Oregon
0.68
.04*
.83
Bend nursery
(irrigated)
Lava Butte
(not jrrigated)
Racial studyt
(not irrigated)
7-13
1.51
0.51
9-15
.87
.29
0-30
.55
.16
Diameter C.rowth, .inches
0
100
200
.51
.46
.49
.51
.54
.48
.53
.49
.43
.28
.17
.06
.63
.02*
.25
*A value of 0.05 or less is considered evidence of significance.
t Probability that the relationship between growth rates across three levels
of N- fertilizer is either linear (PL) or quadratic (P Q) for a given level of P
fertilizer.
rows was done at the beginning of the growing season, side-ditch
irrigation was applied several times during the growing season,
and weeding was carried out within and adjacent to the plots.
Initial height and dbh. of each tree was measured to the
nearest 0.1 foot and 0.1 'inch, respectively, before growth began
in 1957. Height growth, measured at the end of each growing
season through 1962, \Vas selected as a criterion of response to
treatment because the trees were free to grow. However, dbh.
was measured at the end of the 1962 season to supplement height
data.
Foliage, sampled as a composite from the three trees on each
plot, was analyzed for N concentration by the Kjeldabl method
(1) and for P by an adaptation of the Fiske-Subbarow method
(1) employing wet oxidation with nitric, sulfuric, and perchloric
acids.
Soil samples \Vere collected in 350-cc cylinders for bulk density
determination and loose samples were taken for chemical analysis.
Total N was determined by the Kjeldahl method (1) and P by
extraction with NaHCOa· (14).
Conelets and cones \Vere counted at the beginning and end of
each growing season. Analysis of growth and foliage nutrient
data indicated that magnitude of measurements differed signi­
ficantly between years but effect of treatment did not. Therefore,
averages of yearly measurements of these factors are compared.
RESULTS AND DISCUSSION
*Years from planting 2-0 stock. t Largest one-third of trees of best growing source (16). meaningful, and ascribe growth rate reductions in this ca.se to
a nutrient imbalance, as found by others (3, 8).
The study site was some\vhat deficient in soil N for good
ponderosa pine growth, as indicated by the, linear growth
response \Vith incre8.'."ing amount of N fertilizer. Concentra­
tion of soil N averaged 0.093 in the upper 6 inches of un­
fertilized soil. Total weight of soil N was about 2,700 lb/acre
to a depth of 18 inches over fractured basalt. Zinke (21)
suggested a soil N content of about 3,000 lb/acre to a depth
of 48 inches as a minimum requirement for good nutrition of
ponderosa pine, an amount not greatly exceeding that found
in the shallo\v soil of- the Bend Nursery site.
Irrigation may have removed a great part of the limitation
on ponderosa pine growth in the .study area. Irrigated trees
measured as controls in this study grew much faster than
unirrigated trees nearby (Table 2). Increased growth of
ponderosa pine under irrigation has been noted also in two
recent studies. Mosher (13) found diameter growth of 90­
. year-old ponderosa pine increased 1393 when he applied two
40-hour summer irrigations in north-central Washington, but
only 293 when he applied fertilizer at the rate of 67 lb/acre
elemental N without water. In Arizona, Water applied weekly
a rates of 1 and 2 acre-inches increased diameter growth Of
ponderosa pine 1.5 and 2 times, respectively, over that of
unirrigated trees (11).
Growth
With no P fertilizer, height growth increased as the amount
of N fertilizer was increased (Table 1). With N-200, height
growth increased by about 6 o/0 over that of unfertilized trees.
With N-400, height growth was almost 193 greater than that
of controls. Diameter growth also tended to increase with
increasing amount of N fertilizer, but differences were not
statistically significant.
When N-200 and P-100 were applied together, height
growth increased about 153 and diameter growth increased
about 63 more than unfertilized trees. When N-400 and
P-100 were applied i_n combination, both height and diameter
growth were less than values attained "rith N-200 and P-100
together, and we're little different from values obtained with
unfertilized trees.
With P-200 added to all levels of N, height and diameter
growth rate tended to be reduced as the amount of N fertilizer
was increased, although the relationship was not quite
significant at the 53 level of probability. From a practical
consi_deratibn, however, \Ve consider this ielationship to be
Foliage Nutrient Content
l\t1aximum differences in foliage N concentration averaged
only 0.2% dry-weight basis, between treatments within
years. In the absence of P fertilizer, foliage N concentration
tended to increase as amount of fertilizer was increased, but
differences were not significant (Table 3).
When P-100 was applied, addition of N treatments caused
a linear increase in foliage N concentration. Wi_th P-200,
addition of N caused a linear decrease in foliage N concentra­
tion. The latter change in foliage nutrient content was the
only one associated with a growth change, in this case a
reduction.
Maximum differences in foliage P concentration were also
small, averaging only 0.053, dry-weight basis, between
treatments within years. Increasing amount of N fertilizer
had no significant effect on foliage P, either in the absence of P
fertilizer or when P-200 was applied. With P-100, increasi:p.g
N caused a linear decrease in ·foliage P concentration-an
opposite effect of the same treatment on foliage N.
798
SOIL SCI. SOC. Al\1ER. PROC., VOL.
30, 1966
Table 3-Foliage nutrient concentration---eifect of levels o f
fertilizer P across all levels o f fertilizer N (average of
measurements 1, 2, 4, and 6 years after first fertilizer
application)
Phosphorus
fertilizer,
lb/acre
Nitrogen, lb/acre
Probabilityt
400
200
0
Foliage N Concentration,
0
200
400
1.63
1.59
1.63
Foliaoe
0
200
400
0.18
.20
.20
PQ
0.12
.01*
.04*
0.13
.09
.45
3
1.69
I.75
1.55
1.61
1.62
1.61
PL
SO IL N total lb/acre to 18 inc es
NO FERTILIZER
P Concentrr1tion, %
0.19
.18
.17
0.21
.19
.20
0.35
.04
.02
0.01*
.79
.02*
N 400 lb/acre twice
•
P 200 lb/acre twice
•
*Value of 0.05 or less is considered evidence of significance.
t Probability that the relationship between. foliage N concentrationS across
three levels of N fertilizer application is either linear (PL) or quadratic(P q)
for a given level of fertilizer.
Decreased foliage P concentration has also been found in a­
number of tree species other than poilderosa pine when
substantial amournts of N fertilizer were applied (3, 5, 8, 18).
A decrease in foliage P after N fertilization has been ascribed
to an "antagonistic" effect between N and P. Whether results
of the current study represent true "antagonism" or merely a
dilution effect from increased foliage production is not kno'\\•n
because absolute amounts
of
nutrients \Vere not
foliage
determined.
Over all years of this study, foliage P concentration averaged
0.19% and ranged from 0.13 to 0.24%.
These values agree
closely with.those found for some other forest tree species
(IO)
and even with data from a study of 130 peach orchards in
California in which foliage P averaged 0.19% and ranged from
0.14 to 0.27% (9).
Poorest growth of peach trees was
frequently associated with the highest soil P content and best
growth with lowest soil P.
Phosphorus fertilizer had only
slight or no effect on growth of a variety of orchard trees _in
several Western USA States (15).
Foliage N/P ratio in Japanese larch
(Larix leptolepis Sieb.
and Zucc.) was correlated with growth (4, 8) and has also been
suggested as a promising criterion for diagnosing N deficiency
in Douglas-fir
[Pseudotsuga menziesii
(Mirb.) Franco] (5).
In our study, however, there was no apparent relationship
between foliage N/P ratio and growth, perhaps -because a wide
range of foliage nutrient concentrations must be studied to
obtain meaningful correlations between growth and foliage
nutrient supply (18).
0
20
SO IL
40
60
BO
!PO
P total lb/acre to 18 inches
Fig. 1-Soil N and P 6 years after fertilizer was first applied­
unfertilized plots vs. those twice receiving N at 400-lb. acre
rate or P at 200-lb. acre rate.
stantially greater soil N under heavy P fertilizer treatment,
however, cannot be dismissed as readily.
Although the study
did not include analysis of soil microbial populations, a
reasonable explanation for increased soil N in this case might
be greatly increased nitrogen fixation by nonsymbiotic bacteria
whose population growth was enhanced by favorable environ­
mental conditions under irrigation.
Amount of N aHCOa-soluble P '\\'as not different between
unfertilized soil and that receiving N-400 twice (Fig. 1).
However, where P-200 had been applied twice, ainount of soil
P was 91 lb/acre, more than 5 times that of the unfertilized
soil which contained 17 lb/acre.
-Residual soil P from the
fertilizer applications is thus estimated at about 74 lb/acre,
nearly 0.2 of the total amount applied.
Soluble phosphate fertilizers may remain available for at
least 7 years after application to Western USA soils (15).
Most data indicate that residual soil P is directly related to
amount of fertilizer applied.
A relatively large amount of
NaHCOa-soluble P remained in an eastern Oregon soil 6 years
after P had been applied at the rate of 210 lb/acre (7).
How­
ever essentially no residual P was found after 6 years when P
had been applied at 53 lb/acre or less. This experiment,
although conducted "'ith agricultural crops, included several
of the factors dealt with in our study: an irrigated soil of
near-neutral pH in eastern Oregon; application of treble
superphosphate; and evaluation of residual P by Na0H3
Residual Soil N and P
extraction 6 years ·after fertilizer was applied.
Fate of applied nutrients is of special interest in this study
By the end of
6 years, 49.3 lb of P were removed in crops-about 24% of the
because as much"" 800 lb/acre N and 400 lb/acre P had been
total P applied.
added in the heaviest treatments.
the end of 6 years) was 67 lb/acre, about 32% of the total P
Six years after fertilizer
was first applied, analyses were made of soil from unfertilized
applied.
Weight of NaHC03 (available P in soil at
·
plots and from plots that had twice received N-400 or P-200.
According to -foliage analysis and growth data from our
Soil that bad twice received N-400 contained only about 5%
study, only a small part of the total fertilizer P applied might
more N than unfertilized soil (Fig. 1). However, soil to which
be accounted for as uptake by trees. Thus, physical and
P-200 had twice been added, had about 11 % more N at
chemical processes in the soil must be responsible for removing
conclusion of the study.
most of the added P from accountability by the NaHC03
Slightly greater N content of soil that had received heavy N
fertilizer applications can be attributed to treat
ent.
Sub-
extraction method.
Reversion of added P to less available
forms was probably a dominant process. High soil Ca content
TARRANT AND SILEN: GROW'l'H AND NUTRIENT UPTAKE OF PONDEROSA PINE
and near-neutral soil reaction suggest the possibility of
formation of a considerable amount of relatively insoluble
compounds of P.
CONCLUSIONS
On a Deschutes loamy sand soil in central Oregon, height
and diameter growth of irrigated young ponderosa pine
increased linearly as amount of N fertilizer was increased from
0 to 400 lb/acre. Addition of P fertilizer in various combina­
tions with N either increased or decreased tree growth
depending on rates used. Ho\vever, even the unfertilized but
irrigated trees, measured as controls in this study, grew much
faster than unirrigated trees nearby.
Concentration of N and P in tree foliage was not affected
"'hen N fertilizer only was applied. When P fertilizer was
added at the rate of 100 lb/acre with Nin increasing amounts,
,
foliage N concentration \'i'as increased and P concentration
decreased.
After 6 years, soil that had received heaviest N applications
contained little more N than did unfertilized soil. Soil that
had received heaviest applicaticins of P had about 11 % more
N. The amount of P was not different between unfertilized
soil and that receiving heaviest N treatment. However, in
soil receiving heaviest P· treatments the amount of soil P was
91 lb/acre-:--more than 5 times that of unfertilized soil.
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