PLEASE DO NOT REMOVE
FROM FILES
FORESTRY ISSUES IN
URBAN AMERICA
Proceedings, 1974 National Convention
Society of American Foresters
New York City - September 22-26
Copyright 1975
Society of American Foresters
IMPACT OF FOREST FERTILIZATION ON WATER QUALITY
IN THE DOUGLAS-FIR REGION -- A SUMMARY OF MONITORING STUDIES
Duane G. Moore
Pacific Northwest Forest and Range Experiment Station
U. S. Forest Service
Corvallis, Oregon 97331
Forest fertilization on a commercial scale began in the Pacific Northwest
in 1965 with the aerial fertilization of a 607-hectare unit in western Oregon.
Under pressures of increasing demands for wood fiber and predictions of timber
supply deficits in the near future, this management practice has received increased emphasis and has grown rapidly. Between 1965 and the end of 1969,
approximately 36,400 hectares were fertilized in western Oregon and Washington. By 1974 this figure increased to over 285,000 hectares. One company
alone fertilized 76,900 hectares in 1973 (Hansen 1974), and the annual rate
of fertilization for the region is approaching 120,000 hectares.
Research on forest nutrition was initiated in the Douglas-fir region in
1949 (Gessel 1969). Laboratory studies first indicated and field trials later
confirmed that low nitrogen availability is the most common growth-limiting
nutrient deficiency in this area. In fact, major commercial coniferous timber
types in the region have responded only to nitrogen. Urea fertilizer formulated as a granule contains 46 percent nitrogen and is physically well adapted
to aerial application. Other nitrogen fertilizers are available and have been
used to a limited extent, but logistical problems of transporting large tonnages into mountainous terrain will continue to restrict their use.
Coincident with the development of forest fertilization as a management
tool, there has been a growing and equally important concern over the possibility of detrimental effects on water quality. Although the total forest
acreage fertilized to date is relatively small and widely scattered, application of 168 or 224 kilograms of nitrogen per hectare to all or a large part of
a forested watershed may increase the amount of this nutrient entering surface
streams. Recognizing this potential hazard to water quality, Federal and
State agencies and private industry have conducted a number of monitoring
studies throughout the Douglas-fir region over the past 6 years. Figure 1
shows the location of 22 water quality monitoring studies that have been conducted in western Oregon and Washington. In addition, two fertilized watersheds were monitored in eastern Washington (Klock 1971), three studies were
conducted in northern Idaho (Loewenstein et al. 1973), and two fertilized
watersheds were monitored in the spruce-hemlock region of southeast Alaska
(Meehan et al. 1974).
These monitoring studies cover a wide range of soils, climate, and vegetative species. Soil parent materials range from recent alluvium, glacial
deposits, and volcanic tuffs, breccias, pumice, and ash to older sedimentary, metamorphic, and basaltic rock. Soils range from deep, well developed
profiles to those that are young, shallow, and skeletal (largely undifferentiated and with more than 35 percent coarse fragments). Climate varies considerably among study sites but is generally characterized by high winter
rainfall, moderate temperatures, and dry summers. Douglas-fir, ranging in
age from 1P years to mature old growth, is the dominant overstory species in
the fertilized stands. Density of both overstory and understory vegetation
varies greatly. Most of the stand types in the Douglas-fir region that are
209
Jirnmycomelately Creek
r" Crest of the
Cascade Range
Trapper Creek
I
Tahuya River
Mill Creek
Waddell Creek
Thrash Creek
Skookumchuck
River
Elochoman River
Newaukum River
Jackson Creek
Fairchilds Creek
Pat Creek
Turner Creek
Roaring Creek
Canyon Creek
t
I
Trout Creek
I
I
Dollar Creek
I
Crabtree Creek
Ne/son Creek
I
1
Row River
Coyote Creek
Spencer Creek
Figure I. Location of forest fertilization - water quality monitoring
studies in western Oregon and Washington.
210
likely to be fertilized are represented.
Other variables represented by the monitoring studies include stream
size, total area treated, proportion of a watershed fertilized, and rate of
application. Affected surface waters range from the small headwater streams
of individual forested watersheds to much larger third and fourth order
streams with drainage basins of several square kilometers. Total area fertilized in eaeh of the monitoring studies varied from less than 40 to 3,100 hectares. Entire small watersheds were fertilized in five studies, but in most
projects the treated area represented only a small percentage of the drainage
basin above the stream sampling station. Depending on the organization conducting the fertilization project, the usual rate of application is 370 or
493 kilograms urea per hectare (168 or 224 kg N per hectare). Two watersheds
in eastern Washington were fertilized at 56 kilograms nitrogen per hectare in
an experimental erosion control seeding program following a severe burn by
wildfire (Klock 1971).
The data obtained from each monitoring study are directly influenced by
time and rate of application, age and density of stand, soil conditions, climate, stream characteristics, and intensity and duration of that particular
sampling program. In addition, the monitoring studies have been conducted
by several different agencies and companies, and the samples analyzed in different laboratories. Therefore, the results obtained are peculiar to the
specific conditions and characteristics of a given project and cannot be extrapolated individually to other field situations. However, we now have
enough individual studies to provide a broad base for drawing some conclusions.
Rather than attempt to present all of the data, results from selected
monitoring studies will be used to illustrate the kind of data obtained. Pertinent information from all of the studies will then be summarized, and conclusions will be drawn from an interpretation of the combined results.
Field studies were initiated at one site in the fall of 1969 to determine how much fertilizer nitrogen, if any, entered streamflow as a result of
The site selected included four small watersheds
fertilization with urea.
at the head of Coyote Creek in the South Umpqua Experimental Forest in southwestern Oregon. Background hydrological data for 6 years were already available, and it was possible to include fertilization as an additional treatment
without confounding other studies already in progress.
These watersheds are typical of the mixed conifer area of southwest Oregon. Each is T9uipped with a 120-degree, V-notch weir gaging station and a
Fischer-Porter—I digital recorder. A standard precipitation gage has been
maintained at Watershed 2 since 1960. In August and September of 1969, automatic proportional stream samplers were installed on each watershed, and sampling started on October 1, 1969. Detailed chemical analysis of streamwater
samples from all four watersheds has been carried out since that time.
In March of 1970, Watershed 2 was fertilized by aerial application of
urea at the rate of 224 kilograms nitrogen per hectare. The boundaries and
gaging station were marked with yellow plastic bunting, and fertilizer traps
were placed along transects across the watershed at three elevations and along
1/ Use of brand names does not imply endorsement by the U.S. Department of
Agriculture.
211
the boundaries to estimate uniformity of application. Urea was applied by
helicopter using a large, forest-granule formulation to avoid dust drift to
adjacent watersheds.
The drainage channel in Watershed 2 is small, and only very little surface water is exposed. Therefore, the total watershed was fertilized, and
no attempt was made to leave an untreated buffer zone. Water quality was
monitored by collecting grab samples at the stream gaging stations on treated
Watershed 2 and on control Watershed 4 during and after fertilization. Following the close interval sampling during the first 6 weeks after treatment,
monitoring continued through use of the automatic proportional samplers.
Pretreatment levels of urea-, ammonia-, and nitrate-nitrogen were 0.006,
0.005, and 0.002 parts per million nitrogen, respectively. Fertilization of
this 68-hectare forested watershed did temporarily increase these nitrogen
concentrations but did not result in toxic levels of any component in streams
draining the treated area. Concentrations of nitrogen in selected samples
collected over the first 15 weeks following treatment are shown in table 1.
Urea concentrations increased slowly and reached a maximum of 1.39 parts per
million urea-N, 48 hours after application started. Ammonia-N increased to
levels only slightly above background concentrations and never reached 0.10
part per million. Nitrate-N reached a peak concentration of 0.168 part per
million in 72 hours, was 0.140 part per million at the end of 2 weeks, and
had returned to near pretreatment levels after 9 weeks. Nitrite-N was never
detected except as a trace.
Table 1. Concentrations of fertilizer nitrogen in selected water samples
collected at Watershed 2, South Umpqua Experimental Forvit, following application of 224 kilograms urea-N per hectare.-1
Date
Time
NH3 -N
Urea -N
2.7
NO -N
3
Total
.002
.040
.069
.067
.107
.150
.168
.117
.092
.140
.030
.021
.022
.004
.002
.006
.010
.493
.318
.272
1.544
.792
.685
.228
.185.183
.040
.031
.035
.004
.002
.006
ppm
3/25
3/26
II
II
3/27
II
II
3/28
4/1
4/8
4/15
4/22
5/6
5/27
6/17
7/8
1/
21
0800
0815
1230•
2025
0805
1640
2005
0805
_,
-
.001
.016
.012
.034
.048
.036
.029
.036
.016
.015
.010
.010
.013
0
0
0
.007
.437
.232
.171
1.389
.606
.488
.075
.007
.028
0
0
0
0
0
0
From Norris and Moore (1971).
Includes both ionized (NH + ) and un-ionized (NH ) ammonia-nitrogen.
4
3
All losses of applied nitrogen as urea occurred during the first 3 weeks.
212
Losses in the form of ammonia-N, even though small, continued for 6 weeks.
During the first 9 weeks after application, loss of applied nitrogen amounted
to only 1.81 kilograms for the entire watershed (table 2).
Table 2. Nitrogen lost from treated Watershed 2 and untreated Watershed 4,
South Umpqua Experimental Forest, during the firiC 9 weeks after
application of 224 kilograms urea-N per hectare.-1
Unit
Urea - N
NH3 - N
NO -N
3
Total
Kilograms N
Watershed 2
Watershed 4
Net loss
Percent of total loss
1/
0.65
0.02
0.63
34.75
1.01
0.05
0.96
53.00
0.28
0.06
0.22
12.25
1.94
0.13
1.81
,100.00
From Moore (1971).
Low streamflow due to limited precipitation throughout the summer and fall
months resulted in essentially no loss of applied nitrogen during the next 24
weeks. Early storm activity in November brought the soil moisture level back
to maximum storage capacity, and in December the nitrate-N concentration in
samples for the fertilized watershed reached a second peak of 0.177 part per
million (fig. 2). Both streamflow and nitrate-N levels remained high through
December and January, resulting in the loss of an additional 23.8 kilograms ap!-.
plied nitrogen. This is 92 percent of the total amount of fertilizer nitrogen
which was lost during the first year.
Total loss of applied nitrogen from the fertilized watershed (68 hectares)
during the fitt year amounted to 25.85 kilograms or 0.38 kilogram of'nitrogen
per hectare (table 3). Over the same period the total amount of soluble inorganic nitrogen lost from the control watershed (49 hectares) was 2.15 kilograms,
or 0.04 kilogram nitrogen per hectare. Data for soluble organic nitrogen, total phosphorus, silica, and exchangeable -cation content.of the stream samples,
including sodium, potassium, calcium, magnesium, iron, manganese, and aluminum,
indicate that there was no apparent effect of nitrogen fertilization on loss
of native soil nitrogen or other plant nutrients. Movement may have occurred
in the soil profile, but there was no measurable change in streamwater quality.
Table 3. Nitrogen lost from treated Watershed 2 and untreated Watershed 4,
South Umpqua Experimental Forest, during the fir year after
application of 224 kilograms urea-N per hectare.- I
Unit
Urea-N
NH -N
3
NO -N
3
Total
Kilograms N
Watershed 2
Watershed 4
Net loss
Percent of total loss
1/
0.65
0.02
0.63
2.44
0.28
0.06
0.22
0.86
From Moore (1971).
213
27.09
2.07
25.02
96.70
28.03
2.15
25.88
100.00
0. 2 -
A.
1. 5
0. 1 -
1. 0
mg/I
O. 5
0.0
„ „
MAR MAY JUL SEP NOV JAN MAR
0. 0
25 29 2 6 10 14
MARCH
APRIL 1970
1970
1971
TOW AFTER APPLICATION
Figure 2. Fertilization of a 68-hectare watershed with 224 kilograms urea-nitrogen per hectare in
March 1970. A. Immediate effect on water quality; B. Effect on nitrate-nitrogen concentration in streamflow for 1 year following fertilization (Fredriksen et al. 1974).
Initial losses of applied nitrogen were largely due to direct application
of urea fertilizer to the drainage channel. These losses were measured first
as an increase in urea-nitrogen and then as a small increase in ammonia-nitrogen, the latter as a result of hydrolysis of urea applied to open water. Nitrate-nitrogen entering the stream shortly after application is probably
leached from the soil immediately adjacent to the stream channel- Approximately half of the applied nitrogen which was lost during the first 9 weeks
after application was due to direct application, and half entered the stream
as nitrate-nitrogen. However, all of the applied nitrogen lost Auring this
9-week period amounted to only 7 percent of the total loss which,c6curred..
over the first year.
7. trt i • •
High streamflow coupled with the second peak in nitrate-nitrogen levels
during the winter storm period accounted for 92 percent of the tot 1pss.
In February and March 1971, streamflow remained high, but most ok..0e.mmbile
nitrogen had already been lost, and nitrate-nitrogen concentratipngs4a4,re-..
turned to near normal. Monitoring of streamwater samples from t0e,pr4teft,
and control watersheds continued through the second and third years following
fertilization, but there has been no further loss of applied nitrogen.
.
Similar data have been obtained in each of the monitoring stuAjgs dpn7:ducted throughout the Douglas-fir region. However, most data arg:pqc,aq complete as in the Coyote Creek study. Peak concentrations of urea-,..ammonia
and nitrate-nitrogen measured at each site during the monitoring,peqo4
lowing fertilization are given in table 4. The monitoring studies are , identified by the name of the stream sampled, and information on time .04,,re of
application and size of area fertilized are shown. The length of. 0p.monitorand
ing period varied from a few weeks following treatment to . 6 or 7
in a few studies monitoring continued at least a full year. Most sampling
continued until the forms of nitrogen being measured had decreased,Fp near
pretreatment levels.
Increases in the concentration of urea-N ranged from very low to a high
of 44.4 parts per million. These increases are due almost entirely to direct
application to surface water, and the peak concentration reached is.
proportional to the amount of open surface water in the treated unit. Buffer strips were * not left along the main streams in a few of the earlier fertilization projects, and peak concentrations reached 15 to 20 parts per million urea-N. In other projects it is not feasible to leave buffer strips because the stream channel is very small, and it is not possible for . the helicopter pilot to avoid direct application. The Coyote Creek site is an example of the latter situation, but the amount of urea entering the stream was
small because the amount of exposed stream channel is small. The high peak
concentrations of urea-N measured in Dollar Creek and Fairchilds Creek are
due to greatly expanded stream drainage systems caused by spring runoff of
snowmelt. A buffer strip was left along Fairchilds Creek, but the expanded
system of small feeder streams still resulted in direct application of fertilizer to a much larger area of surface water than would normally occur.
Forested watersheds of western Oregon and Washington are drained by a
relatively dense network of small tributary streams. Many of these small
tributaries are only a foot or 2 wide and cannot be identified from the air.
Thus, even when buffer strips of 30 to 90 meters are left along main streams
and tributaries, some direct application of fertilizer to water surfaces
still occurs. Peak concentrations of urea-N in the range of 0.5 to 5.0 parts
per million can be expected under these conditions. The high concentration
.215
■
Table 4.
Study site
Peak concentrations of nitrogen in stream samples following forest,/
fertilization with urea in Alaska, Idaho, Oregon, and Washington.Rate of
application
Date of
application
Kg N/ha
Burns Creek
Canyon Creek
Coyote Creek
Crabtree Creek
Dollar Creek
Elochoman River
Fairchilds Creek
Falls Creek
Jackson Creek
Jimmycomelately Creek
McCree Creek
Mica Creek
Mill Creek
Nelson Creek
Newaukum River
Pat Creek
Quartz Creek
Roaring Creek
Row River
Skookumchuck River
Spencer Creek
Tahuya River
Thrash Creek
Three Lakes
Trapper Creek
Trout Creek
Turner Creek
Waddell Creek
Wishbone Creek
562. /
224
224
224
224
224
224
213
168
224
56
224
224
224
168
224
224
224
168
168
224
224
6/
224213
224
224
224
224
224
Treated
area
Urea-N
2/
NH3-N- NO -N
3
Hectares
Oct. 1970
Oct. 1969
Mar. 1970
May 1969
Apr. 1971
Nov. 1969
Apr. 1972
May 1970
May 1969
Apr. 1970
Oct. 1970
Sept.1972
Dec. 1969
Apr. 1970
Sept.1971
Apr. 1972
May 1972
Mar. 1972
Oct. 1972
Sept.1969
Nov. 1972
Oct. 1972
May 1974
May 1970
Apr. 1970
Mar. 1968
Mar. 1972
Dec. 1969
May 1972
562
1346
68
230
34
297
192
263
95
49
513
47
228
38
2463
243
51
267
2630
191
3108
1620
121
69
64
648
352
600
46
ppm
0
15.20
1.39
24.00
44.40
19.10
23.40
n.d.
0.09
0.71
0.62
0.30
0.68
8.60
0.26
3.26
1.75
0.76
0.13
2.63
0.37
27.20
n.d.
0.70
14.00
4.36
2.48
0.30
0
4/
n.d.0.048
0.080
0.490
n.d.
0.280
1.28
0.044
0.040
0
0
0.12
0.32
0.008
0.079
trace
0.040
0.022
0.026
0.123
1.40
0.06
0.13
0.010
0.700
0.046
0.340
0
0 068
'
0.80
0.177
0.25
0.13
4.00
0.828
1.67
0.116
0.042
0.210
0.28
1.32
2.10
0.438
0.388
0.70
0.210
0.044
0.0855/
0.0051.83
1.88
2.36
0.121
0.160
0.243
0.99
0.28
■••
1/
Data included in the table have been provided by the following companies and
State and Federal agencies: Crown Zellerbach Corporation, Camas, Washington;
Weyerhaeuser Company, Centralia, Washington; Willamette Industries, Inc. Albany,
Oregon; Forest, Wildlife and Range'Experiment Station, University of Idaho, Moscow, Idaho; Washington Department of Natural Resources, Olympia, WashingtOn;
Bureau of Land Management, POrtland, Oregon; -Pacific Northwest Water Laboratory,
Environmental Protection Agency, Corvallis, Oregon; and Pacific Northwest Forest
and Range Experiment Station, Juneau, Alaska; Corvallis, Oregon; and Wenatchee,
Washington. See figure 1 for site locations in Oregon and Washington.
2/
3/
4/
Includes both ionized (NH 4* ) and un-ionized (NH ) ammonia-nitrogen.
3
Applied as ammonium sulfate.
n.d. = no data available.
5/
In this study there was no increase in NO -N. Concentration given is back3
ground level.
6/
Applied as ammonium nitrate.
216
of urea-N in Tahuya River resulted when the pilot could not identify the
stream channel and fertilized the required buffer strip along the stream.
The peak concentrations of urea-N, whether high or low, do not persist for
more than a few hours. Concentrations characteristically reach a peak each day
of application and then drop rapidly toward background. Within 3 to 5 days
after fertilizer application is completed levels of urea-N in the stream have
returned to pretreatment concentrations.
Ammonia-nitrogen levels also increased as a result of direct application
of urea fertilizer to open water. Urea is readily hydrolyzed to ammonia-N in
the stream system. Urea applied to forest floor and soil surfaces will not
reach the stream since it hydrolyzes rapidly to ammonium carbonate and is
then held on cation exchange sites in the . soil and forest floor like any other
ammonium salt. Ammonia-N concentrations in the stream are rapidly reduced
through uptake by aquatic organisms and by adsorption on.stream sediments.
Levels
in the streams sampled did increase following fertilization, but ex.
ceeded 0.10 part per million NH -N in only 10 of the projects monitored. The
3
peak concentration of ammonia-N exceeded 1.00 part per million in two studies,
and in each case direct application of urea to the stream was noted. Lower
ammonia-N levels occurring coincident with other high urea-N concentrations
are attributed to lower temperatures at time of application. Peak concentrations did not persist for more than a few hours, although levels of ammonia-N
slightly above background could be detected in some studies for up to 3 and 4
weeks.
Peak concentrations of nitrate-N entering streams following forest fertilization ranged from no increase in Spencer Creek to a maximum of 4.00 parts
per million in a tributary stream of the Elochoman River study. This high concentration of nitrate-N can be attributed at least in part to runoff from ad
jacent agricultural and dairy lands caused by continued heavy rains -following
fertilization. Because of the late fall date of application (Nov. 30 and Dec.
1, 1969), both urea hydrolysis and nitrification of ammonium would be markedly
inhibited by ,cold, wet soils. In contrast, the lack of any increase in nitrate-N in Spencer Creek is attributed - to the Combined effects of a 90-meter
buffer strip along the stream channel, the virtual lack of small feeder and
tributary streams, and very low rainfall. The Spencer Creek site is located
east of the Cascade Range.
The concentration of nitrate-N in stream samples usually reaches a peak
2
to 4 days after spring application of fertilizer. Concentrations then
in
decrease but may remain above background for 6 to 8 weeks. Losses of applied
nitrogen are very small because the maximum concentrations reached are generally below 1 part per million NO 3 -N and streamflow is rapidly decreasing
with the onset of the dry summer season. About half of the applied nitrogen
entering the stream during the first 30 days is from direct application and
is measured as urea- and ammonia-N. The other half enters as nitrate. In
early fertilization projects where buffer strips were either inadequate or not
used, estimated total loss was between 2 and 3 percent of the applied nitrogen.
However, in later projects where direct application to open surface water is
minimized by buffer strips along the main streams and tributaries, measured
losses are less than 0.5 percent.
In monitoring studies where sampling has continued through the first
winter following fertilization, additional peaks in the concentration of nitrate-N have been measured. These peaks usually coincide with more intense
winter storms, and the concentration drops sharply between storms. Maximum
217
concentrations measured are still low and tend to decrease with each successive
storm.
Patterns of nitrate-N loss to streams following early fall application of
fertilizer (Sept.-Oct.) are similar to those following spring application.
However, peak concentrations measured during winter storms may not be as high
because of less time during warm weather for conversion of applied nitrogen to
the nitrate form. The initial peak in nitrate-N concentration also occurs following fertilizer application in November and December. Subsequent peaks during winter storms are similar to those in streams draining untreated areas.
However, additional losses as nitrate-N may occur during the following winter.
Maximum concentrations of urea-, ammonia-, nitrite-, and nitrate-N measured in streams following forest fertilization have not approached levels considered unacceptable in public water supplies (NAS-NAE 1972). Samples were
collected at the intake for domestic water supplies in two of the studies included in table 4. Recommended standards for nitrate-N in drinking water set
the maximum permissible level at 10 parts per million NO -N(highest peak
level recorded was 4.00 parts per million). Nitrite-N has not been detected
at levels above a trace. Un-ionized ammonia is known to be harmful to fish,
and the recommended permissible level is 0.02 part per +million (NAS-NAE 1972).
At the maximum level of total inorganic ammonia-N (NH, plus NH 3 ) measured,
the concentration of un-ionized ammonia is less than 0.002 part per million
(Trussell 1972). There is no recommended standard for urea since this form of
nitrogen is non-toxic at concentrations well above 1,000 parts per million.
Total amounts of applied nitrogen entering streams draining treated areas
are relatively small and should not have any measurable impact on eutrophication in downstream impoundments. Samples collected at points 3 to 5 miles below fertilized units show that the peak concentrations are rapidly diluted
with downstream movement. Both the amount of applied nitrogen entering
streams and the maximum concentrations measured can be kept at minimum levels
by ensuring that adequate buffer strips are left along main streams and larger
tributaries. In addition, fertilizer should not be applied to forested watersheds when the stream drainage system is greatly expanded by spring snowmelt
or heavy storm activity. Following these few guidelines will ensure that forest fertilization is an environmentally acceptable practice.
LITERATURE CITED
Fredriksen, R. L., D. G. Moore, and L. A. Norris. 1974. The impact of
timber harvest, fertilization, and herbicide treatment on streamwater quality in western Oregon and Washington. In: Bernier, B.,
and C. H. Wingett (eds.), Soils and Forest Management, Proc.
Fourth North American Forest Soils Conference. Quebec, Canada.
(In press.)
Gessel, Stanley P. 1969. Introduction to forest fertilization in North
America. For. Ind. 96(10):26-28.
Hansen, Robert A. 1974. Operational forest fertilization: results,
problems, and land-use planning implications. In: Proc. 1973 National Convention, Society of American Foresters, pp. 221-225.
Washington, D.C.
Klock, G. O. 1971. Streamflow nitrogen loss following forest erosion
218
control fertilization. USDA For. Serv. Res. Note PNW-169, 9 pp.,
illus. Pac. Northwest For. & Range Exp. Stn., Portland, Oreg.
Loewenstein, H., F. H. Pitkin, and D. C. Scanlin. 1973. Nitrogen compounds in streams as affected by aerial fertilization of northern
Idaho forests. Univ. of Idaho, College of Forestry, Wildlife and
Range Sciences, Station Paper No. 12, 11 pp., illus. Moscow, Idaho.
Meehan, William R., Frederick B. Lotspeich, and Ernst W. Mueller. 1974.
Effects of forest fertilization on two southeast Alaska streams.
Environ. Qual., vol. 3. (In press.)
J.
Moore, Duane G. 1971. Fertilization and water quality. In: Proc. 1971
Annual Meeting Western Reforestation Coordinating Committee, pp. 2831. Western Forestry and Conservation Assoc., Portland, Oreg.
National Academy of Sciences-National Academy of Engineering. 1973. Water
quality criteria, 1972. Ecological Research Series EPA-R3-73-033,
594 pp., illus. U. S. Govt. Printing Off., Washington, D.C.
Norris, Logan A., and Duane G. Moore. 1971. The entry and fate of forest
chemicals in streams. In: Krygier, J. T., and J. D. Hall (eds.),
Forest Land Uses and Stream Environment Symp. Proc., pp. 138-158.
Oreg. State Univ., Corvallis, Oreg.
Trussell, R. P. 1972. The percent un-ionized ammonia in aqueous ammonia
solutions at different pH levels and temperatures. J. Fish. Res.
Bd. Canada 29:1505-1507.
219