Water quality impacts of forest fertilization with nitrogen and phosphorus

Forest Ecology and Management 121 (1999) 191±213

Water quality impacts of forest fertilization with nitrogen and phosphorus Dan Binkleya,*, Heather Burnhamb, H. Lee Allenb b

a Department of Forest Sciences, Colorado State University, Ft. Collins, CO 80523, USA Forest Nutrition Cooperative, College of Forest Resources, North Carolina State University, Raleigh, NC 27695, USA

Received 17 June 1998; accepted 3 December 1998

Abstract The drinking-water quality of streamwater in forests is typically very good, exceeding the quality of water in areas with other types of land use. Streams draining agricultural lands in the United States average about nine times greater concentrations of nitrate and phosphate than streams draining forested areas. Forest fertilization commonly increases nutrient concentrations in streamwater, and large increases could lead to unacceptable degradation of water quality. This review summarizes information from studies of forest fertilization around the world, and evaluates the responses of streamwater chemistry. In general, peak concentrations of nitrate-N in streamwater increase after forest fertilization, with a few studies reporting concentrations as high as 10±25 (mg N)/l as nitrate. Increases in average concentrations of nitrate are much lower than the peak values, and the highest annual average nitrate-N concentration ever reported was 4 (mg N)/l. Relatively high concentrations of streamwater nitrate-N tend to occur with repeated fertilization, use of ammonium nitrate (rather than urea), and fertilization of N-saturated hardwood forests. Ammonium-N concentrations may also show large peaks following fertilization (up to 15 (mg N)/l), but annual averages remain <0.5 (mg N)/l. Fertilization with phosphate can lead to increased peak concentrations of >1 (mg P)/l, but annual averages remain <0.25 (mg P)/l. No evidence has been reported of detectable effects of forest fertilization on the composition or productivity of stream communities, but more detailed studies may be warranted (especially in relation to P fertilization). Major limitations in current knowledge include the effects of repeated fertilization in short-rotation plantations, fertilization of large landscapes rather than small stands, and the effects of fertilization on streamwater chemistry in tropical plantations. # 1999 Elsevier Science B.V. All rights reserved. Keywords: Forest fertilization; Streamwater quality; Nitrate pollution

1. Introduction The quality of water draining forests is typically higher than the quality of water draining areas under

*Corresponding author. Tel.: +1-970-491-6519; fax: +1-970491-2796; e-mail: [email protected]

any other major land use (USEPA, 1995). In the United States, the concentrations of total nitrogen (N) and phosphorus (P) in water draining agricultural areas are about nine times greater than concentrations found in forested streams (Omernik, 1977). The concentration of nitrate-N, which is particularly important for water quality, average ca. 0.23 (mg N)/l (ˆparts per million) for very large forested watersheds in the

0378-1127/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 1 1 2 7 ( 9 8 ) 0 0 5 4 9 - 0

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United States, compared with 3.2 (mg N)/l for streams in large agricultural watersheds (Omernik, 1976). Although the overall quality of water draining forest landscapes is very high, some forest practices may signi®cantly alter water quality. Road building and harvesting can substantially increase sediment concentrations in streams, and harvesting and fertilization may increase concentrations of nutrients (Binkley and Brown, 1993a, b). In 1972, Groman called attention to the need for a review of the effects of fertilization on water quality, and the need to develop a larger database for assessing these impacts. Many studies (including several reviews) were produced in the next 25 years, and the reviews generally concluded that forest fertilization poses little or no risk to water quality parameters (cf. Tamm et al., 1974; Fredriksen et al., 1975; Norris et al., 1991; Bisson et al., 1992; Binkley and Brown, 1993b; Shepard, 1994; Burnham and Allen, 1997). Forest fertilization is a basic component of most intensively managed plantation forests around the globe (summarized by Binkley et al., 1995). The most widespread practice is fertilization with nitrogen, or nitrogen plus phosphorus. Nitrogen is commonly applied as urea (especially in North America), ammonium nitrate (particularly in Europe), or diammonium phosphate (particularly in the southeastern US). In the southeastern US, ca. 350 000 ha of pine plantations were fertilized in 1996 (NCSFNC, 1997). The wood ®ber produced by this fertilization would be enough to support about two medium-sized pulp mills. The average cost of fertilization in this area is ca. US$ 200 to $ 225/ha, with a value of the growth response (cumulative over 6±8 years) of ca. $ 250 to $ 1000/ha, depending on tree size, location, and local market. More than 2.3106 ha of forests have been fertilized in this region. Operational fertilization is also high in the Paci®c northwestern US, with ca. 50 000 ha/year fertilized in the late 1980s. Very little operational fertilization is practiced in British Columbia, even though the forests are as responsive as those south of the border. Fertilization is a common practice for Japanese plantations, with ca. 50 000 ha/year fertilized. Australia and New Zealand also fertilize between 30 000 and 45 000 ha of forests annually in each country. In Europe, fertilization practices have differed substantially among countries and over time. Norwegian

forests typically did not receive fertilizer additions (only ca. 6000 ha/year in the late 1980s), when Swedish forests were heavily fertilized (ca. 100 000 ha/ year). From the late 1980s to the present, fertilization in Sweden declined to ca. 30 000 ha/year, including non-N nutrients. The decline in fertilization in Sweden has been driven primarily by concerns about N deposition (Binkley and HoÈgberg, 1997). We are not aware of statistics on rates of fertilization of fast-growing tropical plantations, but the extent is enormous. Brazil alone has ca. 6106 ha of plantation, and common practice includes fertilization with N and P at least once in a rotation (Gonc,alves et al., 1998). In this review, we present a brief overview of the major drinking water quality criteria that apply to streams from forested areas. We focus on major potential issues regarding water quality: nitrate-N, ammonium-N, and phosphate-P. We use histograms to synthesize information from published studies on the effects of fertilizer on water quality in streams and in deep-soil drainage waters. A more detailed version of this review, including tabulated values for water chemistry, has been published as a technical bulletin by the National Council for Air and Stream Improvement (NCASI, 1998). We do not include aspects of water quality such as aluminum concentrations and acidity, as these are not related to drinking water standards, and are not substantially affected by N and P fertilization. 2. Water quality criteria High concentrations of nitrate (NO3ÿ) in stream water are of concern because of possible human health risks if the water is used for drinking. High levels of nitrate have been linked with methemoglobinemia (blue-baby) syndrome in human infants. The USEPA has set a drinking water guideline of 10 (mg N)/l as nitrate (USEPA, 1986), and this standard is also used in Canada (CCREM, 1990). The World Health Organization and European Community use a standard of 50 mg/l as nitrate, which equals 11.3 (mg N)/l as nitrate-N (Anonymous, 1980). Typically 97% of human intake of nitrate comes from food rather than water, and the link between drinking-water nitrate and methemoglobinemia is not well established. A recent

D. Binkley et al. / Forest Ecology and Management 121 (1999) 191±213

review for the US National Academy of Sciences concluded that the current drinking-water standard is clearly adequate for protecting health (Wogan et al., 1996). Safe concentrations for livestock are set considerably higher, between 100 and 300 (mg N)/l (Council for Agricultural Science and Technology, 1974, National Academy of Sciences, 1974). Nitrate is also a major nutrient source in many aquatic ecosystems, and variations in nitrate concentrations below this drinking-water standard may affect the productivity of aquatic ecosystems. No standards have been set, however, for minimizing changes in aquatic ecosystems. The USEPA (1998) has begun the process of de®ning water-quality criteria aimed at protecting aquatic ecosystems from nutrient enrichment, and new criteria (based on natural levels of variation among states) may be available by the year 2003. Nitrite (NO2ÿ) is another potentially toxic form of oxidized nitrogen in streamwaters, but this form is highly transient (being oxidized rapidly to nitrate), so the standard values (1.0 mg/l chronic for drinking water) may never be reached in natural waters. The concentrations of nitrate in major river systems span a broad range at a global scale. In North America, major river systems average <1 (mg N)/l as nitrate, with many systems substantially below this concentration. Europe has higher nitrate concentrations in rivers, with averages as high as 4 (mg N)/l. The high values in Europe are attributed largely to fertilization practices in agriculture, though high rates of atmospheric deposition of N may also play a role (GEMS, 1997). Ammonia (NH3) is a potentially toxic form of inorganic nitrogen. The major water-quality issues surrounding ammonia stem from the release of ammonia (and ammonium) from wastewater sewage systems. The water-quality issues surrounding ammonia deal with toxic effects on aquatic organisms, not on drinking-water quality for human health. Concentrations of ammonia-N as low as 0.03 (mg N)/l are considered potentially toxic as an acute (short-term) concentration, and chronic (long-term) concentrations as low as 0.002 (mg N)/l as ammonia may be toxic (1995 modi®cations of the 1984 criteria; USEPA, 1996). The protonated form of ammonia (sometimes called `ionized' form) is non-toxic ammonium (NH4‡). The

193

equilibrium between the toxic ammonia and the nontoxic ammonium forms depends strongly on water pH (and to some extent on temperature). At pH 9.3, the concentrations of both forms are equal. For each pH unit decline below 9.3, the concentration of ammonia decreases by an order of magnitude. The pH of forested soils typically ranges from 4.0 to 6.5; at these levels, only trace proportions of the ammonia ‡ ammonium pool would be in the toxic form of ammonia. The toxicity of ammonia increases as pH declines, but the equilibrium between ammonia and ammonium works in the opposite direction. To insure that concentrations of toxic ammonia remain low, the USEPA (1996) calls for maximum acute concentrations of ammonium from 21 to 27 (mg N)/l as ammoniumN (which would be in equilibrium with 0.02±0.04 (mg N)/l as ammonia), between a pH range of 6.5±7.0 and temperatures of 58 to 258C. At lower pH values, ammonia is more toxic, but the equilibrium shifts strongly in favor of ammonium; therefore, the allowable concentrations of ammonium-N increase substantially below pH 6.5. For chronic exposures, average ammonium-N concentrations should not exceed 2.0± 2.3 (mg N)/l. The acute exposure (one-hour average) limit is 25±35 mg/l between pH 6.5±7.0 for waters containing salmonid ®sh, and to 37±52 mg/l for other waters. No water-quality criteria have been developed for urea-N, because the compound is not toxic and poses no threat to human health (National Institute of Occupational Safety and Health/Registry of Toxic Effects of Chemical Substances #YR6250000, Material Safety Data Sheet; URL: http://www.chem.utah.edu/ MSDS/U/UREA as of 6/98). The lethal dose (LD50) for rats is of the order of 14 300 ppm (14.3 (mg urea)/ (g of rat mass)). Acute toxicity studies have shown that several thousand (mg N)/l as urea are required for any toxic effects, which is orders of magnitude beyond any observations for forested streams. Phosphate is not toxic, and concerns extremely high concentrations of phosphate center on increase in the productivity of aquatic ecosystems with increasing P supplies. MacDonald et al. (1991) noted that the USEPA has set no standard for P in freshwaters, but a variety of suggested guidelines may relate to avoiding major effects on aquatic ecosystems. Suggested guidelines range from ca. 0.025 to 0.1 (mg P)/l as

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total-P. The P concentration of streams draining into lakes or reservoirs may be more critical than the P concentrations in other streams. Across the United States, the average P concentrations of streams draining large forested areas is ca. 0.02 mg/l, compared with 0.15 for streams draining large agricultural areas (Omernik, 1977). Concentrations of P in river waters in Europe are generally higher than in North America, ranging from 0.05 to 0.5 (mg P)/l across northcentral Europe (GEMS, 1997). In addition to the issues that relate to human health, degradation of water quality through increased concentrations of limiting nutrients could impact the productivity and species composition of aquatic ecosystems. A variety of studies has examined the effects of fertilizer application directly into streams (summarized by Bisson et al., 1992). Nutrient additions typically increase primary production (algal growth), and may increase the size and growth rates of ®sh (cf. Perrin et al., 1987; Peterson et al., 1985). In some cases, fertilizer application has been used to intentionally improve ®shery production. None of the studies reported by Bisson et al. (1992) found evidence of any detrimental effect of direct application of fertilizer to streams. Studies on the effects of forest application of fertilizers on stream ecosystems have shown no effects; background variation along stream reaches are typically too large relative to any minor and transient effects of elevated streamwater nutrient concentrations to allow detection of any impacts on the biota (cf. Meehan et al., 1975; Stay et al., 1979; GoÈthe et al., 1993). 3. Streamwater responses to fertilization Fertilizer applications may alter streamwater chemistry across temporal and spatial scales. Urea fertilization typically leads to immediate increases in urea-N concentrations in streams, particularly if streams are not avoided during application of fertilizer. Urea hydrolysis is generally rapid in forest soils, leading to rapid formation of ammonium either in streams or in soils near streams (Tisdale et al., 1985). Ammonium oxidation forms nitrate over periods of weeks to months following fertilization, and may lead to leaching of nitrate into streams. Ammonium concentrations tend to increase over a period of weeks or months, and

Fig. 1. Springwater nitrate-N concentrations in Sweden following fertilization with 115±175 (kg-N)/ha (data from Tamm et al., 1974).

nitrate concentrations may increase over a period of a year or more (Bisson et al., 1992). The pattern of P concentrations may be intermediate, determined by the rapid addition of P during fertilization, and the slow movement of P into the stream over time from soils near the stream. Nutrient concentrations tend to become diluted relatively quickly downstream from fertilized areas, as a result of nutrient uptake, transformation into gases, or dilution with additional water. (Fig. 1) Without fertilization, the peak concentrations of nitrate-N observed in most forested streams are <1.0 mg/l (Fig. 2; original studies described in Appendix A). Some forested streams with N-®xing species (such as red alder in Oregon) may have higher peak concentrations even without disturbance or fertilization (Brown et al., 1973). Most fertilization studies have shown peak concentrations of nitrate-N of <2.0 mg/l, but several studies have shown much higher peaks, from 10 to 30 mg/l. The highest values come from several studies in the Fernow Experimental Forest in West Virginia. Forests at this site appear to be almost `nitrogen-saturated' (Adams et al., 1997), and fertilization of these forests led to high nitrate-N concentrations in streamwater, regardless of the form of N applied (urea, ammonium nitrate, ammonium sulfate). Hardwood forests in this area are not operationally fertilized with N for increasing productivity. Annual average streamwater concentrations of nitrate-N are almost always <1.0 mg/l for unfertilized

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Fig. 2. Maximum (upper) and average (lower) concentrations of nitrate-N for control and fertilized watersheds (X-axis divisions are 1 (mg N)/l up to 10, then 5 (mg N)/l divisions).

Fig. 3. Maximum (upper) and average (lower) concentrations of ammonium-N for control and fertilized watersheds (X-axis divisions are 1 (mg N)/l up to 10, then 5 (mg N)/l divisions).

watersheds, and <5 mg N/l for all reported cases following fertilization. Fertilization did not degrade water quality relative to drinking water uses (standard of 10±11.3 (mg N)/l as nitrate, depending on country), considering that even high peaks of nitrate concentration typically last a few days or weeks at the most, and that dilution in downstream waters should reduce high nitrate concentrations by more than an order of magnitude within several km of the fertilized site (cf. Hetherington, 1985). Ammonium-N concentrations are very low for unfertilized streams (Fig. 3), for both maximum concentrations and annual averages. Fertilization typically has only marginal effects on ammonium concentrations, except when N fertilizer is added as ammonium nitrate. In no cases were the streamwater standards for ammonium-N exceeded. The concentrations of total-N showed substantial increases in peak concentrations, and these cases resulted from either high concentrations of nitrate

or the input of fertilizer (especially urea-N) to streams. The highest observed concentration of urea-N was 44 (mg N)/l as a result of urea prills directly applied to the streams, but this concentration is more than an order of magnitude below any toxicity threshold. These increases in N following fertilization may provide an opportunity for increased productivity of aquatic ecosystems, but the available studies suggest little if any response in stream productivity following fertilization. Perrin et al. (1984) found that fertilization of a watershed (with and without buffer strips along some streams) and a lake within the watershed increased lake chlorophyll concentrations by about threefold. Stay et al. (1979) found that fertilization of a watershed in Oregon (with buffer strips along streams) showed no discernible effects on salmon mortality, algal growth, benthic community composition, and litter decomposition in the stream, and found no signs of any fertilization effect.

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mental. We expect that the transient timing of increases in P concentration, coupled with P removal and dilution downstream, probably result in little overall effect on aquatic ecosystems, but this expectation may warrant direct examination. 3.1. Role of unfertilized buffer strips in regulating streamwater response

Fig. 4. Maximum (upper) and average (lower) concentrations of total-P for control and fertilized watersheds (X-axis divisions are 0.05 (mg P)/l up to 0.5, then 0.5 (mg P)/l divisions).

Average concentrations of total-P were generally low in all control streams (Fig. 4), although some of them may have exceeded suggested criteria for avoiding high aquatic productivity (MacDonald et al., 1991). Forest fertilization increased the average P concentrations several-fold, perhaps suf®ciently to increase aquatic productivity. Maximum concentrations were substantially greater than the average concentrations for control and fertilized areas, indicating common transient peaks in concentrations. The data indicate that application of P fertilizer to forests may increase streamwater P concentrations enough to produce an increase in productivity of aquatic ecosystems. Only a few studies have directly examined the effects of forest fertilization with P on stream ecosystems, and these focused on N fertilizers only. As noted earlier, direct applications of P to streamwater led to increased production in some streams, but these increases were viewed as bene®cial rather then detri-

In some operations, unfertilized buffer strips have been retained along streams to reduce the impacts on water quality, and the Washington State Department of Natural Resources recommends 45-m wide buffer strips be retained when possible. A variety of studies have documented the ef®cacy of forested buffer strips in moderating ¯ows of chemicals from agricultural lands into streams. Comerford et al. (1992) reviewed the effects of forest buffer strips, and found that 80% or more of the nitrate leaching from agricultural areas was retained within streamside forest buffers (original studies by Doyle et al., 1975; Lowrance et al., 1984; Peterjohn and Correll, 1984; Rhodes et al., 1985; Schipper et al., 1989). Phosphate removal by forested buffers was more variable, ranging from 0% to 99%. How important are buffer strips in minimizing the effects of forest fertilization on water quality? Forest buffers in agricultural landscapes may be very different from unfertilized forest buffers within forests. Only one study directly assessed differences in streamwater chemistry between applications with and without buffers. Perrin et al. (1984) found that a 50-m buffer strip reduced concentrations of urea and ammonium by about an order of magnitude (relative to the treatment without buffer strips), and reduced the concentration of nitrate by ca. 60%. The reduction in urea and ammonium resulted from less direct input of fertilizer to the streams, and the reduction in nitrate probably resulted from the reduced effects on soil chemistry near the stream. The direct application of fertilizer into streams increases the concentration of urea. Given the nontoxic nature of urea, and the fact that subsequent ureolysis in the streams does not produce toxic levels of ammonium, the direct input of urea does not appear to pose a threat to water quality. We examined the value of buffer strips for reducing nitrate inputs to streams by comparing the results of

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substantially degrade water quality, so there is no evidence that buffer strips are needed to prevent water degradation. 3.2. Dependence of streamwater nitrate concentrations on fertilizer form and rate

Fig. 5. Maximum (upper) and average (lower) concentrations of nitrate-N for fertilization with, and without, buffer strips (upper: X-axis divisions are 1 (mg N)/l up to 10, then 5 (mg N)/l divisions).

fertilization studies that included buffers with those that did not (Fig. 5). No strong pattern was apparent; the frequency of high or low concentrations (peak or average) of nitrate in streams following fertilization was similar for studies that used buffer strips and those that did not avoid streams. In several cases, the research design called for retention of unfertilized buffer strips along streams, but the actual treatment resulted in an indirect application of fertilizer to streams (cf. Loewenstein et al., 1973 Dollar Creek site of Fredriksen et al., 1975). If treatment objectives were poorly met in a research setting, the risk of failing to meet objectives in an operational setting could be substantial. We conclude that retention of unfertilized buffer strips may reduce the increases in urea-N and perhaps ammonium-N in streamwater, but the effects on nitrate concentrations are likely to be smaller. In any case, the studies without buffer strips did not

As noted in Fig. 1, streamwater nitrate concentrations tend to increase more by the application of ammonium nitrate than by urea, at least when unfertilized buffer strips are not retained. No studies are available to compare the form of fertilizer with streamwater responses with, and without, buffer strips. In at least one study, nitrate concentrations in streams were shown to increase with the number of times fertilizer was applied in a rotation. Bisson et al. (1992) report unpublished results from a study with 23 fertilized stands. Streams in unfertilized stands averaged ca. 0.3 (mg N)/l as nitrate, compared with 0.6 mg/l for areas fertilized once, and 1.0 mg/l for areas fertilized two or three times. Studies that examined soil drainage water in some cases documented increasing N concentrations with increasing N application rates (e.g. Ring, 1995; BerdeÂn et al., 1997). Few studies have directly examined the relationship between fertilizer dose and streamwater nitrate concentrations, so we looked for patterns across all studies. In terms of peak nitrate-N concentration, there was no signi®cant relationship among the studies (r2 ˆ 0.05, p < 0.1). The rate of fertilization had a clearer effect on the average nitrate concentration, with the fertilization rate accounting for 26% of the variation in post-fertilization nitrate concentrations (p ˆ 0.03). We conclude that the rate of fertilizer application may affect streamwater concentrations of nitrate, but also note that relatively high rates of fertilization typically do not lead to nitrate levels that exceed water-quality standards. 4. Soil drainage water responses to fertilization In addition to the streamwater information discussed above, many fertilization experiments have characterized the impacts on soil-drainage water beneath the zone of the majority of tree roots.

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Soil solutions with low concentrations of nitrate-N following fertilization would pose no threat to streamwater quality. Substantial increases in concentrations of nitrate-N in deep soil solutions following fertilization may indicate a potential for increased streamwater concentrations. High concentrations of nitrate-N in soil water may, or may not, lead to streamwater impacts, depending on factors such as nitrate retention in the stream biota, nitrate removal (denitri®cation), and nitrate dilution from mixing with other water. We know of no study that has followed the effects of forest fertilization with `water-chemistry pro®les' of nutrient concentrations through various soil pro®les and into stream water. All studies appear to have focused either on soil solutions or streamwater, but not both. The histograms for soil-drainage water (see below) are generally higher than those for streamwater (see above), in both control and fertilized cases. We expect that nutrient concentrations should decline substantially between soil drainage water and streams, but intra-site comparisons are needed to determine the common magnitudes of these declines. Further, some of these plot-level studies applied much greater doses of fertilizer or sludge than were used in the watershedscale studies. These studies show that concentrations of nitrate-N in soil-drainage waters is generally <3 mg/l for unfertilized soils, frequently rising to peaks >10 mg/l after fertilization (Fig. 6; description of studies in Appendix B). A substantial portion of studies found that average concentrations remained >10 mg/l for at least a year after fertilization. The highest values are probably not representative of operational fertilization practices. The research projects with the highest, sustained concentrations of nitrate-N in soil-drainage water involved treatments such as repeated annual fertilizations (van Miegroet et al., 1994), weekly irrigation with fertilized water (Henry et al., 1994), or heavy applications of N-rich sludge (Emmett et al., 1995). The loblolly pine study by Wells et al. (1985) may be an exception; fertilization in combination with site preparation is not unusual, and may represent situations where nitrate leaching could be substantial. We note again, however, that concentrations of nitrate in soil-drainage water should be higher than concentrations in streams as a result of N removal or dilution with water from other areas.

Fig. 6. Maximum (upper) and average (lower) concentrations of nitrate-N in soil drainage water for control and fertilized watersheds (X-axis divisions are 1 (mg N)/l up to 10, then 5 (mg N)/l 213 divisions).

Ammonium in soil-drainage water remains fairly low, even after extreme rates of N addition (Fig. 7). No evidence of any water quality threats is apparent. 5. Synthesis Twenty-®ve years ago, Groman (1972) called attention to the need for a larger database for assessing the effects of forest fertilization on water quality. Several dozen studies from around the world are now available to provide general insights on the effects of forest fertilization on water quality. Forest fertilization commonly leads to moderate increases in streamwater nutrient concentrations. The greatest increases come from the following: 1. direct application to streams; 2. use of ammonium nitrate forms of fertilizer; and 3. the application of high rates (or repeated doses).

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Fig. 7. Maximum (upper) and average (lower) concentrations of ammonium-N in soil drainage water for control and fertilized watersheds (X-axis divisions are 1 (mg N)/l up to 10, then 5 (mg N)/l divisions).

Even in these situations, the impact may be too small to degrade water quality. Some of the highest concentrations of nitrate following fertilization came from nitrogen-saturated forests (such as the hardwood forests at Fernow, WV), and these forests would not be fertilized operationally to increase growth. The quality of water draining forests is much better than the quality of water draining agricultural lands, whether or not the forests are fertilized. No evidence of changes in aquatic ecosystems has been reported from forest fertilization operations, but few studies have attempted direct examination of the response of aquatic organism to fertilization of adjacent forests. In some cases, the increases in P concentrations may be high enough so that an increase in biological productivity of streams could be expected; however, more direct studies would be needed for conclusive evidence. Studies on direct additions of N and P to streams have not indicated any negative effects on stream biota, and in some cases ®shery

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scientists and managers have fertilized streams to enhance productivity. Several other areas of research could provide a broader picture of the effects of fertilizers on streamwater quality. It has been dif®cult to extrapolate from plot-level studies of soil-drainage water to watershedscale impacts on streams, and no studies have documented both the effects on soil-drainage water and stream chemistry. A few studies that documented the changes in nutrient concentration as water passes from soils to streams would allow for clearer interpretation of existing studies that documented effects only on soil drainage water. We emphasize that we found no information from tropical areas. The impacts on streamwater quality might be greater in intensively managed plantations in tropical environments. Heavy and repeated applications over large stand areas could lead to greater impacts on water quality than reported for less-intensively managed situations in temperate forests. The use of fertilizers has been increasing in many forest regions, and in some cases fertilizers are being applied several times in a single rotation, to an entire watershed rather than to single stands. More research is needed on large-scale application of fertilizer to intensively managed, short-rotation forests, documenting nutrient changes in both, soil-drainage water and streamwater. Acknowledgements This project was funded by the National Council for Air and Stream Improvement, and by McIntire±Stennis appropriations to Colorado State University. We thank Jim Shepard, R. Giesler and several anonymous reviewers for help in locating references, and for suggestions that improved this review. Appendix A Streamwater responses to forest fertilization Table 1. Appendix B Response of soil drainage water to forest fertilization Table 2.

Table 1 Streamwater responses to forest fertilization Location, stand type

Treatment (kg/ha)

Application method

Chemical concentration (mg/l) nitrate-N maximum

Southern US Piedmont, North Carolina, loblolly pine

Coastal plain, Florida, slash pine Coastal plain, North Carolina, loblolly pine Coastal plain, North Carolina, loblolly pine Coastal plain, North Carolina, loblolly pine

Florida, slash pine, 1±5 year old

Central/Northeastern North America Fernow, WV, mixed

prefertilization

ground, streams avoided

110 N as ammonium nitrate, 24 P, 47 K, 13 S prefertilization

annual average

170 N, 28 P as urea DAP control

ground, streams avoided

145 N, 24 P as DAP control

ground, streams avoided

210 N, 40 P as urea and DAP control

aerial, streams not avoided

225 N, 90 P, 45 Ca

ground, applied over four years, buffer retained by streams

0.1

maximum

annual average

maximum

annual average Sanderford, 1975

<0.1 0.4

0.9

Fisher, 1981

0.9

Campbell, 1989

2.7 0.1

1.2 0.7

0.8

3.8 0.11

0.04

9.3 1.1

0.7

0.18

0.07

1 0.31

0.14 0.02

0.12 0.81

0.04 0.12

1.1 1.22

0.8 0.68

0.07 0.052

0.03 0.015

0.14

0.03

3.63

0.51

14

1.59

1.11

0.170

1.1

0.2

0.23

<0.1

1.5

0.2

0.7

<0.1

0.76 19.8

Fernow, WV, mixed control hardwoods

4.86 0.8±1.1

ground, streams avoided

annual average

phosphate-P

0.1

0.6

aerial, stream channels not avoided

organic-N

0.2

0.1

1970±1971 prefertilization

S-facing slope, 335 N as ammonium nitrate 45 P triple super P, three-years postfertilization control

maximum

<0.1 ground, streams avoided

260 N as urea, 1971± 1972 postfertilization

ammonia-N

0.1

40 N, 50 P prefertilization

Reference

11

0.23 0.9

Fromm and Herrmann, 1996 Herrmann and White, 1996

Riekirk, 1989

Aubertin et al., 1973

0.13

2

0.01±0.02 Helvey et al., 1989, Edwards et al., 1991 0.01±0.04

0.6±0.8

0.02

Fernow, WV, mixed hardwoods

Bear Brook ME, northern hardwoods

Quebec, balsam fir, white spruce, paper birch

NW-facing slope, 335 ground, streams avoided N as ammonium nitrate, 45 P as triple super P control watershed 1984±1988 control watershed 1989±1993 220 N, 275 S as ammonium ground application to sulfate, total from five entire watershed annual applications prefertilization 75 N, 87 S as ammonium sulfate, applied at 1/3 rate for three years control watershed

aerial, stream not avoided

150 N as urea

aerial, stream channels not avoided

Pacific Northwest, North America Cascade, OR, control, upstream reach 25-year-old Douglas-fir 225 N as urea 225 N as urea Southern Oregon, mixed conifer old-growth plantation Central Oregon, second growth Douglas-fir

Coastal Oregon, young Douglas-fir plantation Central Oregon, young Douglas-fir plantation Western Oregon, 35-year Douglasfir plantation Cascade mountains, WA, second growth Douglas-fir

1.5

0.75

0.01±0.03

<0.001

Adams et al., 1997

0.78±1.11 <0.001 0.78±1.71 <0.001

0.4

0.3

0.03

1.0

0.7

0.02

0.4

0.3

1.3

3.5

Norton et al., 1994

Gonzalez and Plamondon, 1978 15 as urea

0.15 aerial, stream not avoided aerial, streams avoided

control stream

225 N as urea

13

aerial with buffer strips for streams

2.8

0.25

24 0.002

0.005

0.001

0.05 0.012

<0.01

0.1±0.2

0.006

0.1±0.5

0.02

0.011

<0.01

0.1±10 (urea)

0.006

0.29

aerial, streams avoided

225 N as urea prefertilization

aerial, streams avoided

225 N as urea prefertilization

aerial, streams avoided

Fredriksen et al., 1975

0.2 0.007

prefertilization

225 N as urea prefertilization

Malueg et al., 1972

2.1

0.01

0.32 0.06

0.13

0.49 0.2

Fredriksen et al., 1975 8.6 (urea)

0.03

0.07

0.49 0.007

0.1±0.2

0.03 0.1

Stay et al., 1979

Fredriksen et al., 1975 44.4 (urea) Fredriksen et al., 1975

0.02

3.3 (urea) 0.8

0.9

Bisson et al., 1992

Table 1 (Continued ) Location, stand type

Treatment (kg/ha)

Application method

Chemical concentration (mg/l) nitrate-N

Coast range, WA, second growth Douglas-fir

Olympics, WA, 10-year Douglas-fir plantation Olympics, WA, 40-year Douglas-fir plantation Washington, burned ponderosa pine seeded to grass

Northern Idaho, 60±70 years Douglas-fir, lodgepole pine

Northern Idaho, 30-year Douglas-fir, grand fir

Northern Idaho, 50-year grand fir Mitkof Island, SE Alaska cutover land

Reference

ammonia-N

organic-N

phosphate-P

maximum

annual average

maximum

annual average

maximum

annual average

2.2

0.8

0.9

0.08

90

1

1

0.6

0.9

0.03

0.3

0.2

225 N as urea, aerial, streams not avoided postfertilization, four months prefertilization

4

1.5

0.3

0.07

50

1

0.005

0

225 N as urea prefertilization

aerial, streams avoided

0.04

225 N as urea prefertilization

aerial, streams avoided

56 N, 65 S as ammonium sulfate prefertilization 54 N as urea one month prefertilization

225 N as urea, postfertilization, six months prefertilization

aerial, streams not avoided

0.002 (urea)

0.04 0.034

0.0

0.01 0.0

0.0

aerial, streams not avoided

0.1

0.0

0.0

0.0

0.1 0.2 0.25

0.0

0.0 0.0 <0.1

0.0

aerial, streams not avoided

aerial, streams not avoided adequately

225 N as urea, seven months postfertilization 225 N as urea, two weeks postfertilization control watershed

aerial, streams not avoided adequately aerial, streams not avoided adequately

210 N as urea

aerial, stream channels not avoided

annual average

Bisson et al., 1992

Fredriksen et al., 1975

0.71 (urea) 0

0.12 0.0

225 N as urea, one-month postfertilization control, upstream reach

maximum

Fredriksen et al., 1975 07 (urea) Klock, 1971

Klock, 1971 0.15 (urea)

0.25

<0.1

1 (urea)

0.4

<0.1

0.12 (urea)

1.1

<0.1

1.75 (urea)

0.32

0.30 (urea)

0.22

0.1

0.10

0.05

1.6

0.5

0.12

0.1

Loewenstein et al., 1973

Loewenstein et al., 1973

Loewenstein et al., 1973 Meehan et al., 1975

control watershed 210 N as urea Vancouver Island Lens Creek, second growth Douglas-fir

Vancouver Island, Canada, Douglas-fir

Europe Loch Ard Forest, Scotland, Sitka spruce plantation

Central Sweden, Scots pine and Norway spruce

Sweden, 21 stands of Scots pine

Sweden, 26 stands of Norway spruce

Central Sweden, Norway spruce

aerial, stream channels not avoided

0.21 2.36

two control watersheds

0.1 0.3

0.22 1.28

0.0±0.3

225 N as urea, 46% of watershed fertilized 225 N as urea, 80% of watershed fertilized 2±3 km downstream control watershed

aerial, stream channels not avoided

200 N as urea

aerial, stream channels not avoided aerial with 50 m buffers

0.00±0.06

0.5

0.54

9.3

0.9

1.9

0.8 (urea)

0.7 0.22±0.11

0.15 0.005

0.36 0.01±0.015 <0.004

0.16 (urea)

0.22±0.79

0.53±4.78

0.1±0.19

0.195±0.472

0.000± 0.119

Hetherington, 1985

2.7

control watershed

14 (urea)

Perrin et al., 1984

0.126

163 N as urea, 47 P ‡ 104 K control, upstream reach

ground application to portions of the watersheds

150 N ammonium nitrate

aerial, stream channels not avoided

2.7±3.5

0.42±0.53

0.04

150 N calcium ammonium nitrate controls

0.303

<0.03

2.48

0.19±0.23 0.28

0.007

Harriman, 1978

0.004± 0.137 GoÈthe et al., 1993

0.02

8.2

0.107

11.1

0.02

29.6

0.066

15.4

0.012

0.00±0.03

115±175 N as urea, two-years postfertilization, spring water sampled control

Tamm et al., 1974

0.2±1.0

0.0±0.3

115±175 N as ammonium nitrate control 120 Ca, 30 P, 30 Mg, 20 K, `Skogs Vital'

0.05 0.08

Tamm et al., 1974

0.2±10

ground application

<0.02

0.42

0.22

<0.1

<0.02

0.23

0.20

1.7

Ring and Nohrstedt, 1993

Table 1 (Continued ) Location, stand type

Treatment (kg/ha)

Application method

Chemical concentration (mg/l) nitrate-N maximum

Kloten, central Sweden control 155 (kg N)/ha as urea

GaÊrdsjoÈn, southwest Sweden, uneven-age Norway spruce/Scots pine

Aneboda, southern Sweden, uneven-age Norway spruce Pacific New Zealand, radiata pine

160 (kg N)/ha as ammonium nitrate before fertilization

150 (kg N)/ha as ammonium nitrate 150 (kg N)/ha as ammonium nitrate

ammonia-N annual average

maximum

aerial application, stream channels not avoided aerial application, stream channels not avoided

annual average

maximum

0.02 4.4

0.23 9.9

22

25

6.0

4.0

0.30

phosphate-P annual average

Shiga Prefecture, Japan, Pinus thunbergii plantation 740 N wastewater application, four years

annual average Grip, 1982

0.005

2.2

Westling and Hultberg, 1990

0.09 We s t l i n g a n d Hultberg, 1990

0.0

1.38

0.02

0.0

5.11

15.05

0.32

0.04

prefertilization 54 P as superphosphate, 100 N as urea 40 P as superphosphate

maximum

0.35

0.02 aerial, stream channels not avoided

organic-N

0.01 0.06

0.012

control, upstream reach 230 N as urea

New Zealand, radiata pine

aerial, stream channels not avoided

Reference

0.02 aerial, stream channels not avoided

Leonard, 1977

Neary and Leonard, 1978

0.109 0.26±0.56

control

0.15

0.05

irrigation

1.2

0.5

1.72 Iwatsubo and Nagayama, 1994

0.01

0.04

0.003

Table 2 Response of soil drainage water to forest fertilization Location, stand type

Treatment (kg/ha)

Application method, period

Chemical concentration (mg/l) nitrate-N maximum

Eastern North America North Carolina, midrotation loblolly pine

225 N as ammonium nitrate, 60 P as triple super P, 135 K as KCl Florida, slash pine 34 N, 13 P, 28 K ‡ plantation micronutrients Arkansas, 3±4 year 140 N as urea and loblolly pine plantation ammonium nitrate Arkansas, uneven-aged shortleaf/ loblolly pine

230 N as urea and ammonium nitrate

Georgia, 15-year loblolly pine

control 225 N

Coastal Plain, SC, loblolly pine age 1

225 N, 55 P 225 N, 44P, 110 K control 400 N as liquid sludge

single ground application, 12 lysimeter samples at 120 cm depth, three-years postfertilization single application, sampled with groundwater wells at 80 cm applied over two years, water <6 sampled at 90 to 360 cm depth, two years applied over two years, water 25±30 sampled at 90 to 360 cm depth, two years <0.1 single application, sampled by 0.1 ceramic lysimeter at 90 to 150 cm depths, one-year postfertilization 0.1 0.55 9.5 single application, sampled with fritted-glass lysimeters at 1 m depth, two-years postfertilization

800 N as liquid sludge

Coastal Plain, SC, loblolly pine age 3

630 N as solid sludge 50 N, 55 P as diammonium phosphate control 400 N as liquid sludge

800 N as liquid sludge 630 N as solid sludge

single application, sampled with fritted-glass lysimeters at 1 m depth, two-years postfertilization

ammonia-N annual average

maximum

organic-N annual average

maximum

phosphate-P annual average

maximum

Reference annual average

<1

<0.1

Wells et al., 1975

<7

<3

Segal et al., 1987 Wheeler et al., 1989 Wheeler et al., 1989 Grant, 1991

2

0.05

12

0.07

35±60 depending on site prep. 35-72 depending on site prep. 10 28

12

0.08

2.5 6

0.05 0.03

2.4

0.8

0.05

7

2.1

0.36

12.6 2.8

6.4 1.09

0.05 0.1

Wells et al., 1985

Wells et al., 1985

Table 2 (Continued ) Location, stand type

Treatment (kg/ha)

Application method, period

Chemical concentration (mg/l) nitrate-N

Coastal Plain, SC, loblolly pine age 28

control 400 N as liquid sludge

Tennessee, 1±5 year yellow poplar plantation

800 N as liquid sludge 630 N as solid sludge control 300 N as urea

300 N as urea

Tennessee, 1±5 year control loblolly pine plantation 300 N as urea

annual average

0.5

0.2

0.06

4.2

1.5

0.25

34 0.5 2.5

17 0.15 0.4

0.3 0.5

three applications, 1/year, sampled 7 with ceramic lysimeters at 40 cm depth, three years of fertilization, plus one postfertilization year 12 applications, 4/year, sampled 15 with ceramic lysimeters at 40 cm depth, three years of fertilization, plus one postfertilization year 2.5

control 450 N as urea

single dose after planting

18

450 N as urea 450 N as urea 450 N as urea

three installments in three years nine installments in three years 50, 150 and 250 installments in three years

25 11 21

maximum

organic-N

maximum

three applications, 1/year, sampled 5 with ceramic lysimeters at 40 cm depth, three years of fertilization, one postfertilization year 12 applications, 4/year, sampled 5 with ceramic lysimeters at 40 cm depth, three year of fertilization, one postfertilization year 0.2

300 N as urea

Oak Ridge, TN, shortrotation sycamore

single application, sampled with fritted-glass lysimeters at 1 m depth, two-years postfertilization

ammonia-N annual average

maximum

phosphate-P annual average

maximum

Reference annual average Wells et al., 1985

Johnson and Todd, 1988

2

5

0.2

Johnson and Todd, 1988

0.8

1.4

0.1 4 year 1 <0.2 year 2,3 8 3.5 4 year 1 2 year 2 14 year 3

van Miegroet et al., 1994

Michigan, 10-year aspen coppice

335 N as liquid sludge

50±70-year red pine, jack pine

400 N as liquid sludge

50±70-year northern hardwood

785 N as liquid sludge

50±70-year mixed oak

400 N as liquid sludge

Western North America Coastal British 450 N as urea Columbia, 16-year old Douglas-fir Western Washington, Douglas-fir

California, various conifers

single application by tractor, sampled tension lysimeters at 1.2 m depth, four years postapplication ground water at 3±8 m single application by tractor, sampled tension lysimeters at 1.2 m depth ground water at 3 to 8 m single application by tractor, sampled tension lysimeters at 1.2 m depth ground water at 3 to 8 m single application by tractor, sampled tension lysimeters at 1.2 m depth

single application, sampled with 4.5 fused alundum disks at 75±85 cm depth, eight months after fertilization

control 47 000 sludge, 2000 N, mature forest 47 000 sludge, 2000 N, young forest 47 000 sludge, 2000 N, clearcut 225 N as urea

Europe BillingsjoÈn, Sweden, 360 N total in four install100-year old Scots pine ments at five year intervals

720 N total in four installments at five year intervals 1080 N total in four installments at five-year intervals 1440 N total in four installments at five year intervals

11.5

Hart et al., 1988

2.5 11.5

Hart et al., 1988

1.2 1.7

Hart et al., 1988

0.2 3

1.8 (eight- 0.1 months average)

Hart et al., 1988

0.1

4.7

2.0

1 ground, soil water at 50 cm depth, one-year postfertilization

Otchere-Boateng and Ballard, 1978

Henry et al., 1994

57 10 25

single application, sampled with 6.1 ceramic lysimeters at 120 cm depth, three years postfertilization

1.8

Miles and Powers, 1988

ground, water sampled by ceramic lysimeters at 50 cm depth, before logging three-years postlogging before logging

0.03

0.18

0.04±0.25 0.03

0.06±0.31 0.16

three-years postlogging before logging

0.02±0.21 0.04

0.11±0.41 0.18

three-years postlogging before logging

0.03±0.65 0.03

0.08±0.71 0.15

Ring, 1995, Ring, 1996

Table 2 (Continued ) Location, stand type

Treatment (kg/ha)

Application method, period

Chemical concentration (mg/l) nitrate-N maximum

1800 N total in four installments at five-year intervals Central Sweden, three stands of 35±55 year Norway spruce, high N deposition site

Central Sweden 35± 55-year old Scots pine, low N deposition site

Southeast Sweden, mixed age Scots pine and Norway spruce

0.04±1.7 0.54

three-years postlogging

0.23±4.0 0.11

single ground application, sampled with ceramic lysimeters at 50 cm depth, three years postfertilization

150 N, 1000 lime control

150 N as ammonium nitrate

single ground application, sampled with ceramic lysimeters at 50 cm depth, three-years postfertilization

control 150 N, 1000 lime control

70 N as ammonium nitrate

StraÊsan, Sweden, 22± control 45-year old Norway spruce N1: 730 kg N/ha as ammonium nitrate over 20 year N2: 1700 kg N/ha as ammonium nitrate over 20 years

annual average

three-years postlogging before logging

control

150 N ammonium nitrate

ammonia-N

irrigated weekly for two years, sampled with polylysimeters at 70 cm depth, two-years posttreatment start tension lysimeters at 30 cm depth, data for last five years of experiment single ground application

27

5

48

4 <0.04

maximum

organic-N annual average

maximum

phosphate-P annual average

maximum

Reference annual average

0.11±1.9 0.78 0.35±4.2 0.23

Nohrstedt, 1992

<0.03

Nohrstedt, 1992

10

<1

10 0.5

0.02±0.04 <1 0.06

0.03

0.1

0.03

0.03

0.01

0.00

0.4

0.01

5.2

1.4

0.35

0.01

16.1

5.0

0.6

0.2

0.06±0.19 Stuanes et al., 1995

BerdeÂn et al., 1997

Scania, southern Sweden, 120-year old beech

Klosterhede Denmark, 59-year Norway spruce (all plots NPK fertilized 5, 10 and 15 years before this study)

Klosterhede Denmark, 75-year Norway spruce Wales, 32-year Sitka spruce

North Wales, 45-year old Sitka spruce

Fichtelgebirge, Germany, 20±40 year Norway spruce plantation

control

tension lysimeters at 30 cm

4.1

0.92

60 (kg N)/ha as ammonium nitrate, total of 25 applications 180 kg N/ha as ammonium nitrate, total of 25 applications control

single ground application

35

4.8

60.5

4.9

0.01

0.00

0.01

0.01

ground, soil water at 45 cm depth

120 N as ammonium nitrate, 21 P, 140 K, 43 Ca, 8 Mg, 37 S control poly/glass-lysimeters at 55 cm

0.1

0.1

0.02

0.01

35 N as ammonium nitrate control

monthly irrigation

0.6 5.6

0.2 2.5

0.02

0.01

88 N as sodium nitrate

weekly irrigation for 2.5 years, sampled by ceramic lysimeters at 50 cm depth

17

9

30.8 11 3.0

15 5 2.0

3.3

2.3

3.5

1.5 0.1

188 N as sodium nitrate 88 N as ammonium nitrate control 60 P as dihydrogen phos phate, 100 K as potassium chloride 120 P, 200 K control

single ground application, sampled with ceramic ysimeters at 60 cm depth

70 N, 200 K as potassium nitrate, 200 Mg, 250 S as magnesium sulfate, 40 P, 10 000 lime control 70 N, 200 K as potassium nitrate, 200 Mg, 250 S, as magnesium sulfate, 40 P, 10 000 lime

single ground application to healthy stand, sampled with ceramic lysimeters at 90 cm depth

Tyler et al., 1992

Ingerslev, 1997

Gunderson and Rasmussen, 1995 Emmett et al., 1995

Stevens et al., 1993

Hantschel et al., 1990

3

0.1 single ground application to `de clining' stand

6

Table 2 (Continued ) Location, stand type

Treatment (kg/ha)

Application method, period

Chemical concentration (mg/l) nitrate-N maximum

Solling, Germany, 135-year beech

Solling, Germany, 100-year Norway spruce

control

annual average

maximum

organic-N annual average

maximum

phosphate-P annual average

maximum

Reference annual average

<1

265 N, 115 Ca, 170 K, 4 Mg, plus two doses of lime (total 1960 kg Ca) control

fertilization in 1973, limed in 1975 and 1980

265 kg N, 115 Ca, 170 K, 4 Mg, plus two doses of lime (total 1960 kg Ca)

fertilization in 1973, limed in 1975 and 1980

Pacific Tasmania, Australia, control logged, burned, and seeded with Eucalyptus 200 N, 230 S as ammonium sulfate

ammonia-N

Matzner et al., 1983

12 (4 following liming) 3

single ground application, sampled with ceramic lysimeters at 30 cm depth

100 P, as superphosphate 200 N, 100 P North Island, New 450 N as urea (4 times/year single ground application, Zealand, regenerated for 2.5 years), following sampled with ceramic radiata pine plantation whole-tree harvest and forest lysimeters at 60 cm floor removal 450 N following whole-tree harvest 450 N following stem-only harvest 450 N following stem-only harvest, extra slash added Various harvesting and organic matter treatments, no fertilization ACT Australia, 10-year 400 N as ammonia, 100 P at two applications two months radiata pine triple superphosphate, 720 S, apart, sampled with ceramic 400 Ca, 6 Mg, 100 K, 10 B lysimeters at 40 cm depth

40 (10 following liming)

Matzner et al., 1983 5±10

0.45

1.3

0.01

0.05

2.2

0.15

0.27 0.19 46

1.6 3.9

0.09 0.26

12

24

8

18

8

25

12

2±15

1±5

37

12 (sixmonths)

Adams and Atti will, 1991

Smith et al., 1994

60

8 (six months)

Khanna et al., 1987

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