Operational liming of surface waters in Sweden

From 1977 to 1982, liming of acidified waters was performed for a trial period using governmental subsidies. Based on the experience gained, an operational liming program was started in 1982 by the National Environmental Protection Board of Sweden. All waters with pH of less than 6 and/or an alkalinity of less than 0.05 meq L^?1 have been eligible for subsidies. Individual water owners as well as organizations and federal agencies may apply for subsidies. Normally 85% of the costs are covered by government grants. Each county administration draws up a 5 yr liming plan and applies yearly for subsidies on a county basis. Since 1977, SEK (Swedish Kroner) 373 million have been spent on liming operations and SEK 33 million on administration and follow-up studies. A yearly budget of about SEK 110 to 130 million has been proposed for 1988 to 1991. The liming agent used has been powdered CaCO₃ with a particle size normally of 0 to 0.2 mm. At present, about 4,000 lakes have been treated. The results of the treatments are normally evaluated by analyzing water samples taken twice a year. These are analyzed for pH, alkalinity, conductivity, color, Ca and Mg. In addition, biological surveys are carried out in selected lakes and streams.     

Can forest-soil liming mitigate acidification of surface waters in Sweden?

Acidification of surface waters and forest soils is severe in large parts of southern Sweden. The shallow groundwaters are also affected. Large scale liming of surface waters and streams is in operation, often combined with wetland liming to limit the effects of acid episodes, e.g. at snow melt. Acid episodes are perhaps the most severe problem in limed surface waters and in many as yet well buffered waters, because of temperature-layered acid inflow, often superficial. As a result of some investigations, a large scale forest liming programme covering 6.500–10.000 km² was recently suggested. The main objectives of this forest liming programme are to retard cation depletion and to prevent nutrient imbalance and forest decline in acidified areas. This paper deals with the effects of forest soil liming on streams and surface waters. The response of water chemistry is very dependent on hydrological and soil properties. Although pH itself may be little affected by liming, the acidity (or negative ANC) decreases, inorganic Al-species decrease and the Al/BC-ratio increases in the runoff water. Especially interesting is that this is also true during acid episodes. This means that toxicity for acid sensitive biota decreases. These results indicate that large scale liming may have beneficial effects on surface water chemistry. Furthermore, as surface waters are expected to respond to smaller decreases in acid deposition than do forests soils, forest soil liming may allow less frequent liming of lakes. Consequently, forest soil liming in combination with the anticipated emission reductions may have very beneficial results on surface waters in certain areas of Sweden.     

Differences in response to liming in a lake-dwelling fish community

The Lake Fjorda water system in southern Norway consists of several lakes which exhibit a gradient in acidification. The system is inhabited by populations of brown trout, Arctic char, whitefish, perch, European minnows and Crucian carp. Populations of Arctic char, whitefish and brown trout were nearly wiped out in some of the locations, as a result of acidification, In 1985, Lake Fjorda was limed in order to improve water quality so the fish community would be recovered. Fish stock assessment by means of gill-net fishing in the epibenthic and pelagic zones was carried out before (1983) and three years after liming (1991–1993). Populations of Arctic char and whitefish have not recovered after eight years of liming. Brown trout are almost extinct and do not seem to be recovering. Perch were less affected by acidification, exhibiting good recruitment also before liming.     

Effects of liming on carbon and nitrogen mineralization in coniferous forests

A temporary decline in tree growth has often been observed after liming in coniferous forests poor in N but seldom in forests rich in N. To test the hypothesis that the decline was caused by decreases in N supply, C and N mineralization were estimated in incubated soil: (1) after liming in the laboratory, and (2) after earlier liming in the field. Liming increased the C mineralization rate in needle litter, nor humus and 0 to 5 cm mineral soil for a period of 40 to 100 days at 15°C. After that period, liming had no effect on the CO₂ evolution rate in materials poor in N (C:N ratios 30 to 62) but increased the CO₂ evolution rate in materials rich in N (C:N ratios 24 to 28). When liming induced nitrification, the CO₂ evolution rate was reduced. Liming resulted in lower net N mineralization rate in needle litter and mor humus. The reduction was more pronounced when NH₄ ⁺ was the only inorganic form than when NO₃ ^? was the predominant form. The reason is probably that chemical fixation of NH₃ and amino compounds increases with increasing pH. Because of the fixation, the incubation technique most likely underestimated the mineralized N available to the roots. Taking this underestimation into consideration, liming initially reduced the N release in the litter layer. In the other soil layers, liming increased the N release in soils rich in N and had only small effects in soils poor in N. For the total N supply to the roots in the litter, humus and 0 to 5 cm mineral soil layers, liming caused a slight reduction in soils poor in N and a slight increase in soils rich in N. Data on tree growth corresponded with these results.The hypotheses that tree growth depressions can be caused by reduced N supply after liming and that tree growth increases can be caused by increased N supply after liming thus seem reasonable.     

Pools and fluxes of carbon and nitrogen in 40-year-old forest liming experiments in Southern Sweden

Soil samples were collected from litter, humus and mineral soil layers to a depth of 50 cm in 37–42 year-old limed and unlimed plots in one beech and three spruce stands in S Sweden for determination of carbon (C) and nitrogen (N) pools, C and N mineralization rates and nitrification rates. The samples were sifted while still fresh and incubated at a constant temperature (15°C) and soil moisture (50 % WHC) for 110–180 days with periodic subsamplings. The C and N pools in the uppermost soil layers were significantly lower in plots limed with 9–10 t CaCO₃ ha^?1 than in unlimed plots, whereas the pools in the deeper mineral soil did not differ markedly between the treatments. In the whole soil profile, the C and N pools had, on average, decreased by 16% (P<0.05) and 11% (P>0.05), respectively, after 40 yrs. The smaller reduction in N pools resulted in significantly lower C:N ratios and increased N immobilization in the limed spruce plots but not in the limed beech plot. C and net N mineralization rates were increased in some of the limed plots and decreased in others. This indicates that liming can still have a stimulatory effect after 40 yrs in some soils. The nitrification potential was increased in the limed plots. Liming did not increase tree growth in the stands investigated. We conclude that liming with high doses of CaCO₃ is likely to reduce pools of soil C and possibly even soil N in relation to unlimed areas in spruce and beech forests in S Sweden. If trees in limed stands do not respond with better growth, the treatment will thus result in a net ecosystem loss of C and N in relation to unlimed areas. It was not possible to conclude whether the effects of low doses of lime would be similar to those of high doses.     

Living lakes: An aquatic liming and fish restoration demonstration program

Living Lakes, Inc. (LLI), a not-for profit organization, sponsors an applied aquatic resources restoration demonstration program for acidified waters. In 1986 and 1987 LLI began evaluation of seven different liming technologies on 22 lakes and 10 streams in 6 states. Lakes and streams have been treated in the states of Massachusetts, Rhode Island, New York, Pennsylvania, Maryland and West Virginia. The Living Lakes program commits to ongoing water quality analysis for the lakes and streams treated for the life of the program and, if necessary, retreatment. Living Lakes has recently begun investigations into the treatment of partial or entire watersheds in conjunction with the Loch Fleet project in Scotland, investigations in the Black Forest in Germany, and studies in the Woods Lake watershed in the Adirondack region of the state of New York, co-sponsored by the Electric Power Research Institute.     

Effects of liming on carbon and nitrogen mineralization in coniferous forests

A temporary decline in tree growth has often been observed after liming in coniferous forests poor in N but seldom in forests rich in N. To test the hypothesis that the decline was caused by decreases in N supply, C and N mineralization were estimated in incubated soil: (1) after liming in the laboratory, and (2) after earlier liming in the field. Liming increased the C mineralization rate in needle litter, mor humus and 0 to 5 cm mineral soil for a period of 40 to 100 days at 15°C. After that period, liming had no effect on the CO₂ evolution rate in materials poor in N (C:N ratios 30 to 62) but increased the CO₂ evolution rate in materials rich in N (C:N ratios 24 to 28). When liming induced nitrification, the CO₂ evolution rate was reduced. Liming resulted in lower net N mineralization rate in needle litter and mor humus. The reduction was more pronounced when NH ₄ ⁺ was the only inorganic form than when NO ₃ ^? was the predominant form. The reason is probably that chemical fixation of NH₃ and amino compounds increases with increasing pH. Because of the fixation, the incubation technique most likely underestimated the mineralized N available to the roots. Taking this underestimation into consideration, liming initially reduced the N release in the litter layer. In the other soil layers, liming increased the N release in soils rich in N and had only small effects in soils poor in N. For the total N supply to the roots in the litter, humus and 0 to 5 cm mineral soil layers, liming caused a slight reduction in soils poor in N and a slight increase in soils rich in N. Data on tree growth corresponded with these results. The hypotheses that tree growth depressions can be caused by reduced N supply after liming and that tree growth increases can be caused by increased N supply after liming thus seem reasonable.     

Effects of stopping liming on abandoned agricultural land

It is suggested that stopping liming on agricultural land could lead to a potential chemical time bomb (CTB). the sequence of interrelated events leading to the CTB include the end of liming, perhaps caused by a change in land use, a progressive decrease in soil pH and increased solubility of potentially toxic contaminants that accumulate in soils as a result of agricultural practices. Data are presented on rates of long-term soil acidification and modelled changes in the solubility of some trace metals in soil as a result of acidification. Soil acidification rates depend primarily on acid input rates and the soil's acid neutralizing capacity, possibly limited by neutralization kinetics. Experimental data illustrating this point show that the pH decreased rapidly in a field soil receiving ammonium rather than nitrate fertilizer treatment. on a limed agricultural field that was later abandoned and converted to deciduous woodland, The pH of the 0-23 cm soil layers decreased over 100 years from pH 7 to 4.2. Deeper layers acidified at a slower rate. Thermodynamic model calculations simulating the solubilities of metals in a sandy topsoil showed zinc, cadmium and aluminium solubilities increasing exponentially with decreasing pH, resulting in several-fold solubility increases between pH 5 and 4. These results suggest how metal solubility increases after liming stops. the model pH-solubility relationships depended on the type of metal, The solid phase controlling the solubility, and the amount of metal in the soil if adsorption controlled the solubility. Decreasing pH and the resultant increase in metal solubility expected on abandoned farmland might be managed through techniques such as liming or planting forests of selected tree species.     

Influence of wetland liming on water chemistry of acidified mountain streams in Lofsdalen,Central Sweden

Acidic precipitation has caused damage to the populations of fish and invertebrates in numerous streams in the southern part of the Swedish mountain range. In the middle of the 70's, the pH of precipitation decreased and has since then frequently been lower than 4.5. Many of the streamwaters were well buffered during most time of the year, but during periods with high discharge, the buffering capacity was completely exhausted, pH frequently decreased to around 4.5 and very high levels of Fe, Mn and Al occurred. In general, base cations (BC) and organic anions decreased during periods of high flow, while SO₄ increased or was relatively independent of flow. On an average, the ratio SO₄/BC was negatively correlated to pH, while organic anions/BC showed a weaker correlation to pH. In order to investigate if wetland liming could be used as a remedial measure in such areas, lime treatments were started in 1983 in the Lofsdalen area, province of Härjedalen. The liming stabilized the alkalinity and pH of the streams at circum-neutral levels, and reduced the leaching of Fe, Mn, and Al. The average levels of these elements decreased and the seasonal fluctuation decreased considerably.     

Water chemistry in forested catchments after topsoil treatment with liming agents in South Sweden

Critical loads of sulphur and nitrogen are exceeded in South Sweden, and nutritional imbalances are expected to appear with time in forests. During 1984 paired catchments were established in a northwestern-southeastern gradient in South Sweden. The aim was to study long-term liming effects on throughfall, soil water, groundwater and runoff. Dolomitic limestone and wood ash were tested at one locality, Hagfors (59° N). Three adjacent catchments were used; one reference area, one treated with dolomitic lime (0.5 kg/m²) in 1985, and one with wood fly ash (0.22 kg/m²) in 1988. The lime and the fly ash was granulated and applied by a helicopter in the end of May. Measurements concerning chemistry of the precipitation, throughfall, soil water and runoff has been conducted since spring 1984. The results showed that top-soil spreading of liming agents, besides the desired effects on soil chemistry, after some years also affected the quality of the recipient water. In the dolomitic lime treated catchment the positive effects were most obvious, with raised pH-, Ca-, and Mg-values and lowered Al-, Fe- and Mn-values. A positive trend regarding lower nitrogen (NO₃ ^?) leaching could also be calculated. Wood ash in the used amount affected only slowly, but after six years the runoff water indicated increased pH-values as well as increased Ca- and K-values and Ca/Al-ratios. Dolomitic lime in the amounts of 0.5 kg/m² was concluded to be sufficient to achieve positive effects in catchments of the present type. Wood ash in the amount of 0.22 kg/m² although enough for recycling purposes, was not sufficient enough in increasing pH in runoff to prevent acid leaching from the forest soils.     

Effects of liming and tillage systems on microbial biomass and glycosidases in soils

This study was undertaken to investigate the long-term influence of lime application and tillage systems (no-till, ridge-till and chisel plow) on soil microbial biomass C (C_mic) and N (N_mic) and the activities of glycosidases (- and -glucosidases, - and -galactosidases and -glucosaminidase) at their optimal pH values in soils at four agroecosystem sites [Southeast Research Center (SERC), Southwest Research Center (SWRC), Northwest Research Center (NWRC), and Northeast Research Center (NERC)] in Iowa, USA. Results showed that, in general, the C_mic and N_mic values were significantly (P <0.001) and positively correlated with soil pH. Each lime application and tillage system significantly (P <0.001) affected activities of the glycosidases. With the exception of -glucosidase activity, there was no lime×tillage interaction effect. Simple correlation coefficients between the enzyme activities and soil pH values ranged from 0.51 (P <0.05) for the activity of -glucosidase at the NWRC site (surface of the no-till) to 0.98 (P <0.001) at the SWRC site. To assess the sensitivity of the enzymes to changes in soil pH, the linear regression lines were expressed in activity/pH values. In general, their order of sensitivity to changes in soil pH was consistent across the study sites as follow: -glucosidase>-glucosaminidase>-galactosidase>-galactosidase>-glucosidase. Lime application did not significantly affect the specific activities (g p -nitrophenol released kg^–1 soil organic C h^–1) of the enzymes. Among the glycosidases studied, -glucosidase and -glucosaminidase were the most sensitive to soil management practices. Therefore, the activities of these enzymes may provide reliable long-term monitoring tools as early indicators of changes in soil properties induced by liming and tillage systems.     

Effects of liming on soil magnesium on some soils in New Zealand

Abstract

Results from 2 pastoral field lime trials showed that liming reduced exchangeable Mg. This effect increased with increasing rate of lime and with time following lime application, and was greatest in the top 0–50 mm depth. Soil solutions, sampled 2 years after liming, showed that solution Mg increased in increasing rate of lime. This effect was greatest in the top 20 mm of soil.

Lime incubation studies indicated that Mg fixation did occur on some of the soil studied, at pH >6.2. However, this did not account for the size of the observed effects of liming on exchangeable Mg in the field or explain the observed effects of liming at pH <6.2.

It is suggested therefore, that the major mechanism by which liming reduces exchangeable Mg, on these soils, is through displacement of exchangeable Mg into solution by the added Ca in lime, and subsequent leaching.

Results from other field trials suggest that liming will decrease exchangeable Mg if the change in pH‐dependent CEC (?ECEC) per unit change in soil pH is <15 me 100 g‐¹.     

Effects of lake liming on phytoplankton production in acidic Adirondack lakes

Phytoplankton community characteristics were monitored prior to and following CaCO₃ addition to two small, highly acidic lakes (Cranberry Pond and Woods Lake) and one larger, less acidic lake (L. Simon Pond). Data were also collected from a control site (Dart's Lake) exhibiting chemical characteristics similar to the pretreatment conditions observed at the experimental sites. In the two small, most acidic lakes, base addition was associated with higher chlorophyll levels during the first summer following treatment. Woods Lake was maintained at a circumneutral pH for 3 yr and exhibited increased phytoplankton abundance throughout the posttreatment period. In contrast, Cranberry Pond reacidified within 1 yr following based addition. Reacidification was accomplished by a decrease in lake chlorophyll levels to pre-treatment levels. At the larger, less acidic lake (L. Simon Pond), liming was associated with lower chlorophyll levels during the first summer after treatment. Reductions in chlorophyll levels at L. Simon Pond reflect the absence of the spring phytoplankton peak and a decrease in phytoplankton growth below the depth of the thermocline. At Cranberry Pond, annual differences in phytoplankton production did not correspond to changes in lake acidity and phytoplankton abundance. Productivity in Woods Lake exhibited an increasing trend during the 3 yr following treatment. Interpretation of treatment effects on productivity was confounded by high between-year variability at the control site.     

Effects of liming on water quality of two streams in West Virginia

In an effort to improve the fisheries potential of many West Virginia mountain streams by increasing the alkalinity and pH, the West Virginia Department of Natural Resources (DNR) is conducting research into the feasibility of a point source limestone application technique. This research was to provide data that would assist in the design of future projects and the selection of appropriate methodology. Thirteen metric t and 33.3 t of 0.64 cm crusher run ground limestone aggregate were applied as a single deposition to Crouch and Yokum Runs, respectively. Limestone was applied to Crouch Run a year prior to treatment of Yokum Run. The point source treatment produced discharge dependent changes in the downstream water chemistry. The pH increased from an average of 4.73 above the application point to 5.70 below. At high stream discharges, the pH dropped, but never to the pretreatment background level. Increases in Ca concentrations and ANC were also observed downstream of the limestone application site. Sediment analysis was performed to determine the calcite concentration within the stream bed by both an instrumental technique (x-ray fluorescence (XRF)) and an HC1 leach technique to indicate the extent of downstream movement and distribution of limestone. The analysis showed both a limited downstream transport and a variable spread of limestone across the stream channel. The XRF and wet laboratory methods of quantifying the calcite content of the sediments were compared. Although statistical analysis indicated a difference in precision between the x-ray fluorescence and HC1 leach methods, the acid leach method can be considered an economical alternative to x-ray fluorescence. Recommendations are made on methods to increase the effectiveness of the point source treatment and the design of future research.     

Effects of acidification and liming on feeding groups of nematodes in coniferous forest soils

Summary Nematodes were sampled in untreated, acidified, and limed plots in a Norway spruce (Fexboda) and a Scots pine (Norrliden) stand. At Fexboda, the total number of nematodes was significantly reduced after the acidification. This reduction was probably due to a shock effect, because the samples were taken only 5 months after an application of 200 kg H₂SO₄ ha^-1 to the forest floor. However, the root/fungal-feeding Aphelenchoides was not reduced, probably because it is more tolerant of high acid concentrations than most other nematodes. At Norrliden, where the samples were taken 7 years after the last application of H₂SO₄, no significant differences were found between the acidified and untreated plots. If the treatment with H₂SO₄ caused similar effects as at Fexboda, the results indicate a recovery of the nematode populations. Decreased predation from lumbricids rather than a recovery of microfloral populations probably allowed this recovery. No marked effect of lime, spread 2 (Fexboda) and 12 years (Norrliden) before the sampling on the numbers of any of the nematode feeding groups was found. This correlated with almost no change in bacterial biomass after liming, while the active fraction of fungal hyphae was unaffected by liming at Fexboda and reduced by liming at Norrliden. A tendency for decreasing numbers of all nematode feeding groups in the limed plots at Norrliden coincided with increasing numbers of lumbricids.     

Effects of liming and selected heavy metals on ammonium release in waterlogged agricultural soils

Many farmlands are periodically flooded or ponded by excessive precipitation resulting in changes to soil chemical and biochemical properties. In this study, one set (eight treatments with four replications) of field-moist surface soils (0–15 cm) and their air-dried counterparts obtained from a long-term liming experiment were incubated at 30 °C under waterlogged conditions for 10 days, and the amounts of net NH₄ ⁺-N released (soluble and exchangeable) were determined after extraction with 4 M KCl. Another set of three surface soils were used to evaluate the effect of six heavy metals on the NH₄ ⁺-N release under waterlogged conditions. Results showed that increasing the liming rate from 0 to 17,930 kg ha^?1 effective calcium carbonate equivalent increased the average soil pH from 4.98 to 7.06, averages of the amounts of NH₄ ⁺-N released ranged from 1.6 to 5.2 mg N kg^?1 field-moist soil, and the corresponding amounts released in air-dried soils ranged from 18.9 to 32.9 mg N kg^?1 soil. This increase of the amount NH₄ ⁺-N released in air-dried soil samples is presumably due to a slaking effect. At 5 mmol kg^?1 soil, all six heavy metals inhibited the NH₄ ⁺-N released. The relative effectiveness of the heavy metals in inhibition of the NH₄ ⁺-N released varied among the three soils. Lead(II) was the most effective inhibitor of NH ₄ ⁺-N release in Clarion and Harps soils and Cd(II) in Harps soil. Cobalt(II), Cu(II), and Cd(II) were the least effective inhibitors of NH₄ ⁺-N release in Clarion, Harps, and Okoboji soils, respectively.     

Effects of liming and fertilization on soil solution chemistry in North German forest ecosystems

The effect of aboveground liming and fertilization as well as ploughing and liming of forest soils on soil solution chemistry was studied in various experimental plots of the German Solling area. Due to low solubility of limestone, aboveground liming had only moderate effects on soil pH and base saturation of CEC. Calcium and Mg concentration increased and Ca/Al and Mg/Al ratios of the soil solution improved. Despite extreme doses of lime, nitrate leaching did not increase in the case of a beech plot. Elevated nitrate leaching was found in the case of a spruce and a beech plot previously fertilized with N. Nitrate concentrations are far from drinking water thresholds in the case of beech. Nitrate levels of soil solution of the unfertilized spruce plot are in the range of 3 to 8 mg L⁻¹. Liming did increase these values slightly in the first years, and nitrate levels reached those of the untreated plot in the following years. Ploughing connected with high liming doses obviously led to inhomogeneous distribution of lime. No significant deacidification of seepage water at a depth of 100 cm occurred because of leaching of sulfate from the industrial lime used. This was followed by Al-leaching. Nitrate levels slightly exceeded drinking water standards throughout the first winter period after the measure. The development of young trees was significantly improved.     

Effects of fertilizer type and rate,and liming on banana squash yield

There is a question whether it is best to use synthetic or alternative materials to fertilize horticultural crops. Levels of applied fertilizer can affect development of crops such as banana squash (Curcubita maxima Duch.). Seed were planted in 1990, 1991, and 1992 into beds treated with sufficient fertilizer to raise the residual nutrient levels to the recommended (base) and twice recommended (2X) rate with a synthetic or an alternative fertilizer. Lime was applied prior to seeding in 1990 and as a treatment was, or was not, applied prior to seeding in 1991 and 1992. Plants grown in beds treated with the synthetic fertilizer consistently produced higher yields than plants grown in beds treated with the alternative fertilizer. In 1990, the base fertilizer rate improved yield. There was no difference in 1991 due to fertilizer level, and in 1992, the 2X fertilizer rate improved yield. Application of fertilizer above the base level is not encouraged. Liming did not affect yield. By the spring of 1992, the soil pH for lime augmented fertilizer treatments was increased above the spring 1991 levels which was maintained through fall 1992. For the no‐lime treatments, soil pH by fall 1992 was below spring 1991 levels. Soil pH was not correlated with yield. These data suggest that factors which would include solubility, mineralization, and leaching of materials may be responsible for yield differences between plants fertilized with synthetic or an alternative fertilizer.     

Effects of forest liming on the nutrient status of podzolic soils in Finland

The results of 40 long-term liming experiments in Scots pine and Norway spruce stands on mineral soil sites of varying fertility are reviewed in this paper. Limestone was broadcast at a dose of 2 t ha^?1 at the end of the 1950s and sampling was carried out at the end of the 1970s. Liming resulted in considerable accumulation (10 to 50% increase) of organic matter in the humus layer, but no changes in the mineral soil. The C/N ratio of the humus increased on the most productive sites. Liming brought about a long-term decrease in acidity of the humus layer on all site types, as well as a decrease in the mineral soil (0 to 10 cm) of the least productive ones. There was also a corresponding increase in base saturation. There was considerable accumulation of B and Mn in the humus layer. Sulphur was found to have been immobilized to a considerable extent in the humus layer, presumably as Al sulfate. Liming at fairly low doses (e.g. 2 t ha^?1) thus seems to be sufficient to counteract any future increases in soil acidification without bringing about any adverse effects (apart from perhaps B levels) on the nutrient status of the soil.     

Effects of forest liming on the nutrient status of podzolic soils in Finland

The results of 40 long-term liming experiments in Scots pine and Norway spruce stands on mineral soil sites of varying fertility are reviewed in this paper. Limestone was broadcast at a dose of 2 t ha^–1 at the end of the 1950s and sampling was carried out at the end of the 1970s. Liming resulted in considerable accumulation (10 to 50% increase) of organic matter in the humus layer, but no changes in the mineral soil. The C/N ratio of the humus increased on the most productive sites. Liming brought about a long-term decrease in acidity of the humus layer on all site types, as well as a decrease in the mineral soil (0 to 10 cm) of the least productive ones. There was also a corresponding increase in base saturation. There was considerable accumulation of B and Mn in the humus layer. Sulphur was found to have been immobilized to a considerable extent in the humus layer, presumably as Al sulfate. Liming at fairly low doses (e.g. 2 t ha^–1) thus seems to be sufficient to counteract any future increases in soil acidification without bringing about any adverse effects (apart from perhaps B levels) on the nutrient status of the soil.