Agricultural and Food Science in Finland 291 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 291–302. © Agricultural and Food Science in Finland Manuscript received August 2000 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 291–302. Soils in a young landscape on the coast of southern Finland Delbert L. Mokma Department of Crop and Soil Sciences, Michigan State University, East Lansing, MI 48824, USA, e-mail: mokma@msu.edu Markku Yli-Halla Resource Management Research, Agricultural Research Centre of Finland, FIN-31600 Jokioinen, Finland Helinä Hartikainen Department of Applied Chemistry and Microbiology, PO Box 27, FIN-00014 University of Helsinki, Finland Soils in an agricultural landscape on the southern coast of Finland (60° 13’N 25° 02’E) were charac- terized and classified according to Soil Taxonomy, the FAO-Unesco system (FAO), and the World Reference Base for Soil Resources system (WRB). The impact of human activity (<500 years) on the soil forming processes was discussed. The cultivated land studied (200 ha, elevation of <1 to 10 m) consists primarily of lacustrine sediments. It is surrounded by forested bedrock high areas dominated by Spodosols/Podzols, and by reedy wetlands, partially occupied by Sulfaquents/Thionic Gleysols. Cultivated pedons had mollic or ochric epipedons and cambic horizons. High base saturation of epi- pedons is likely man-made by liming. These soils have naturally high water tables and the develop- ment of the cambic horizons has been significantly promoted by artificial drainage (ditches >150 years ago, tile lines at the depth of 1 m in the 1950s). They now meet the criteria for Mollisols and Inceptisols (Soil Taxonomy), Phaeozems and Gleysols (WRB), and Cambisols (FAO and WRB) but before drainage were likely Entisols (Soil Taxonomy) or Gleysols (FAO and WRB) with ochric, um- bric, or histic epipedons and without a diagnostic B horizon. Key words: soil formation, artificial drainage, structure, redoximorphic features, catena, Soil Taxon- omy, FAO-Unesco System, World Reference Base for Soil Resources Introduction The landscape around the Gulf of Finland was formed during the last 12000 years. The archae- an granitic bedrock, which is part of the Fenno- scandia Shield and is composed of silicic gra- nitic plutonic rocks and magmatites, was erod- ed by the latest glacier and stratigraphically cov- ered by till or material deposited during several evolutionary stages of the Baltic Sea. The de- velopment of the basin is related to the melting mailto:mokma@msu.edu 292 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Mokma, D.L. et al. Soils of coastal Finland of the ice and the gradual uplift of the earth’s crust which was depressed 800–900 m by the glacier. As a result of isostatic land uplift after glaciation and changes in the water level of the sea, land became exposed to soil forming proc- esses. During the Baltic Ice Lake stage (12000– 10200 BP) and the Yoldia Sea stage (10200– 9500 BP), the Helsinki region was under rather deep water. Signs of the highest shoreline of the Ancylus Lake stage (9500–8500 BP) are locat- ed 50 m above the present sea level (Taipale and Saarnisto 1991). The fine-textured deposits formed at this stage and later on the bottom of the basin are symmictic and contain markedly more organic material than the older ones. Dur- ing the Littorina Sea stage (7500–4500 BP) sa- line water re-entered the basin and gave rise to sediments with high sulphate concentration and biological activity. In the Helsinki region the highest shoreline of this period is about 30 m above the present sea level. The present brack- ish water conditions have prevailed for about 2500 years (Taipale and Saarnisto 1991). Pres- ently, land in the Helsinki area is rising in rela- tion to sea level about 3 mm per year (Eronen et al. 1995, Seppä and Tikkanen 1998). In the national soil classification, organo- genig soils have more than 20% organic matter (OM) and mineral soils less than 20% OM. Min- eral soils are divided into classes according to particle size distribution. Pedogenic features have not been systematically studied in agricul- tural soils and they are not used in natonal soil classification. Finnish contribution to the soil map of Denmark, Finland, Norway and Sweden (Rasmussen et al. 1979) and to the Soil Geo- graphical Databse of Europe (European Soil Bureau 1998), both using the FAO-Unesco clas- sification, is mostly based on the interpretation of topographic maps. Podzolization process mainly in forested soils has been intensively studied in Finland (e.g. Aaltonen 1941, Mount et al. 1995, Righi et al. 1997, Giesler et al. 2000) but only recently have morphological descrip- tions of agricultural soils (Yli-Halla and Mok- ma 1999, Yli-Halla et al. 2000) been published. The emphasis of this study was in relation- ships between the pedons and geomorphology in a very young agricultural landscape. The soil forming processes and their impact on soil prop- erties are discussed as related to the drainage history and cultivation practices. Problems in the classification of these young soils are also pre- sented. The coastal area of the Gulf of Finland is of importance for agricultural production even though the intensive land-use around coast line cities is claiming land for construction of build- ings and roads. The information obtained from the studied area can be extrapolated to corre- sponding landscapes on the shore of the Gulf of Finland. Material and methods The study area was in the research farm of the University of Helsinki at Viikki along the coast about 7 km from the center of Helsinki (Fig. 1). The area consists of cultivated land (200 ha) and of forested bedrock high areas, surrounding the fields on the west, north, east, and partly south. Also, within the cultivated land there are small islands of bedrock highs which usually serve as locations for buildings and support forest vege- tation. The bedrock highs are covered with gla- cial till but the tops are usually exposed bedrock. On the south, the landscape consists of some forested glacial till areas, wetland forests, and a large area of reeds which serves as a haven for many birds. In the fields small grains and grass- es are grown and dairy cows are pastured. The cultivated area is a former bay of the Baltic Sea and consists of lacustrine materials. Agriculture at Viikki began in late Middle Ages, and in 1550 a royal manour was established there. The fields are artificially drained. Drainage was first (>150 years ago) accomplished with open ditches and in the 1950s with subsurface drainage pipes. The fields are surrounded by ditches which empty into a major ditch, at the lowest elevation in the cultivated area, delivering the drainage waters to the sea. 293 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 291–302. Eight pedons were selected to represent the landscape: six pedons on cultivated fields at the elevation of <1 m to 10 m above sea level and two pedons outside the cultivated area, one in the bedrock high area and one in a wetland be- tween the fields and the sea (Fig. 2). The pe- dons were described (Table 1) and sampled in June and July of 1997 according to the meth- ods of Soil Survey Staff (1993). Pedon 5 was not sampled. The rate of land uplift (3 mm per year) was used to estimate the maximum age of each pedon (Table 1). Particle size distribu- tion was determined by a pipette method (Elo- nen 1970) after digestion with hydrogen per- oxide. In this study, clay (<0.002 mm), silt (0.002–0.06 mm), sand (0.06–2 mm) and coars- er materials (>2 mm) were separated. Organic C was determined using a Leco dry combus- tion apparatus (Laboratory Equipment Corpo- ration, St. Joseph, MI). Soil pH was measured in water. In the acid sulfate soils (pedons 7 and 8) pH in water was determined in fresh sam- ples and after six weeks of aerobic incubation. These samples were also analysed for SO 4 -S, extracted with 0.01 M CaCl 2 , and some sam- ples were analysed for total S after digestion with 1.4 M HNO 3 . Base saturation, on the basis of the sum of exchangeable cations, was deter- mined by ammonium acetate extraction (pH 7.0). In one pedon (pedon 1), Fe and Al were extracted with 0.5 M ammonium oxalate (pH 3.0) to check for the presence of spodic hori- zon. Phosphorus was extracted with 1% citric acid to identify anthropogenic accumulation of P in the soil (Soil Survey Staff 1975, FAO 1988). In some fields, soil P status was charac- terized by the soil testing data (an acid ammo- nium acetate method, pH 4.65, Vuorinen and Mäkitie 1955) available at the research farm. In a bedrock high area, the variation in depth to bedrock or thickness of glacial till was de- termined at two meter intervals in a transect located along a street being constructed for res- idential development. The pedons were classi- fied according to Soil Taxonomy (Soil Survey Staff 1998), the FAO-Unesco system (FAO 1988) and the World Reference Base for Soil Resources system (FAO 1998) assuming that the pedons have a cryic temperature regime (Yli-Halla and Mokma 1998). Results and discussion Texture of the pedons Pedon 1 formed in glacial till in a bedrock high area (Fig. 1). The till had more than 70% sand (Table 2). The low content of silt and clay par- ticularly in the E and Bs horizons can be attrib- uted to the washing away of the fine materials by littoral forces. The area around pedon 1 is composed of exposed bedrock and relatively shallow soils. Of the 69 observations made along the transect, 20 percent had depth to bedrock between 0 and 50 cm, 28 percent between 50 and 100 cm, 33 percent between 100 and 150 cm, Fig. 1. The study area is in Helsinki on the southern coast of Finland. 294 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Mokma, D.L. et al. Soils of coastal Finland Fig. 2. Location of the investigated soil profiles. The contour interval is 5 m. © Maanmittauslaitos / National Land Survey of Finland, permission 429/MYY/00. and 19 percent greater than 150 cm. The bare rock resulted from erosion of the till by the Lit- torina phase of the Baltic Sea (Hyyppä 1950). Most cultivated land in this landscape is com- posed of lacustrine materials. Fields that border on bedrock highs usually have greater slope gra- dients than the central parts of the fields which are nearly flat. Pedons 2 and 3 represent culti- vated soils near the major bedrock high areas and they had the highest elevations among the culti- vated pedons (5 and 10 m, respectively). These pedons had sandy upper horizons which are prob- ably beach deposits originating from the glacial till of the neighboring bedrock high areas. In pedon 2, the Ap and Bw horizons contained a substantial amount of material coarser than 2 mm which also reflects the glacial till origin. Both pedons 2 and 3 had lacustrine materials beneath the beach deposits. In pedon 2 glacial till was encountered at 108 cm (4Cg2), whereas till was 295 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 291–302. Table 1. Selected morphological properties and estimated age of pedons. For the classification according to the FAO- Unesco and WRB systems, see Table 3. Horizon Depth Texture Matrix Redoximorphic features Structure cm Helsinki 1, Typic Haplocryod (emerged from water >7000 B.P.) Oa 0–10 sapric 7.5YR 2.5/1 1m pl E 10–14 ls 7.5YR 5/2 1m sbk Bs 14–52 s 7.5YR 4/4 1m sbk BC 52–82 ls 10YR 5/6 1c sbk C 82–143 ls 2.5Y 5/2 c2p 7.5YR 4/4, c2p 10YR 5/6 0 m Helsinki 2, Aquic Haplocryoll (3625 B.P.) Ap 0–36 sl 10YR 3/1 1) 1c pl/1c sbk Bw 36–43 ls 10YR 5/3 1c sbk 2Bg 43–59 c 2.5Y 4/2 m2p 10YR 4/4,c1p 7.5YR 4/6 2c sbk 3Cg1 59–108 sil 10YR 6/1 c3p 7.5YR 4/6 1c pl 4Cg2 108–150 sl 2.5Y 5/1 c3p 7.5YR 5–4/6, c3f 2.5Y 5/3 1vc sbk 1) dry color 10YR 5/2 Helsinki 3, Aquic Haplocryoll (1800 B.P.) Ap 0–35 sl 10YR 2/2 2) 1c pl E 35–43 ls 10YR 6/3 c2p 5YR 4/6, c2p 7.5YR 4/6 1c pl Eg 43–51 ls 2.5Y 6/1 c2p 5YR 4/6, c2p 7.5YR 4/6 1c pl Bg 51–59 sl 2.5Y 4/2 c2p 10YR 4/4, c2p 5YR 4/6 1m pl Cg1 59–99 sl 10YR 6/1 c2p 7.5YR 4/4 1c pl/1f sbk 2Cg2 99–124 cl 2.5Y 5/1 c2p 7.5YR 4/6 1m pr/2m abk 3Cg3 124–170 c 10YR 4/1 f3p 7.5YR 4/4, c2p 10YR 4/4 1m pl/2m abk 2) dry color 10YR 5/1 Helsinki 4, Typic Cryaquept (975 B.P.) Ap 0–30 sicl 10YR 3/2 3) 2f gr Bg1 30–37 c 10YR 4/2 c2p 7.5YR 4/4, f1f 10YR 6/1 2vf sbk Bg2 37–50 c 10YR 5/1 c2p 7.5YR 4/6 2f abk 2Cg1 50–61 sl 10YR 6/1 m3d 10YR 5/6 1m sbk 3Cg2 61–123 c 10YR 5/1 c3p 7.5YR 4/4 0 m 3) dry color 10YR 6/2 Helsinki 5, Typic Cryaquoll (625 B.P. ) Ap 0–36 l 10YR 3/2 4) 1c sbk Bg 36–51 fsl 2.5Y 6/2 c2p 7.5YR 5/6, c2p 10YR 5/6 1c sbk 2BC 51–71 sic 5Y 5/1 c2p 7.5YR 4/4 2c pr 2Cg1 71–110 sic 5Y 5/1 c3p 10YR 4/4 0 m 2Cg2 110–138 sic 2.5Y 5/1 f2f 2.5Y 5/4 0 m 3Cg3 138–163 fsl 2.5Y 5/1 0 m 4) dry color 10YR 5/2 Helsinki 6, Aquic Haplocryoll (100 B.P.) Ap 0–28 c 10YR 3/2 5) 1f sbk and 2m gr Bg1 28–60 sic 10YR 4/2 m2p 7.5YR 4/6, f2d 10YR 5/8 2vf sbk Bg2 60–70 sic 10YR 4/2 c2d 10YR 5/8, c2p 2.5Y 6/4 1m sbk BC 70–100 c 10YR 5/2 m3p 7.5YR 4/6, m3p 2.5YR 3/3 3vc pr/2m abk C 100–117 c 10Y 5/1 0 m 5) dry color 10YR 5/2 continued on the next page 296 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Mokma, D.L. et al. Soils of coastal Finland continued from the preceding page Horizon Depth Texture Matrix Redoximorphic features Structure cm Helsinki 7, Sulfic Cryaquept (325 B.P.) Ap 0–31 sic 10YR 3/3 6) 1f sbk Bg1 31–50 c 10YR 5/2 m2d 7.5YR 4/6 3f sbk Bg2 50–68 c 5Y 5/1 c2p 10YR 5/6 3m pr/3m sbk Bj 68–84 c 5Y 5/1 m3p 5YR 3/3, c2p 7.5YR 4/4 3m pr/3m sbk c2p 2.5Y 6/4 Cg 84–117 c 5Y 5/1 m3p 5YR 3/3, c2p 7.5YR 4/4 3m pr/3m sbk C 117–170 c 10Y 3/1 0 m 6) dry color 10YR 6/2 Helsinki 8, Histic Sulfaquent (0 B.P., mineral soil surface approximately at sea level) Oi 0–25 fibric 10YR 3/2 2f gr Bg1 25–42 l 5Y 3/1 1vc pl Bg2 42–75 sic 10YR 4/1 1m abk Cg1 75–90 c 10YR 4/1 c2p N 3/1 1vf abk Cg2 90–150 c 10YR 5/1 0 m Abbreviations: Texture: c=clay, sic=silty clay, cl=clay loam, sicl=silty clay loam, l=loam, sil=silt loam, sl=sandy loam, fsl=fine sandy loam, s=sand, ls=loamy sand Redoximorphic features: f=few (<2% of surface), c=common (2–20%), m=many (>20%), 1=fine (<5 mm), 2=medium (5– 15 mm), 3=coarse (>15 mm), f=faint, d=distinct, p=prominent Structure: 0=structureless, 1=weak, 2=medium, 3=strong, vf=very fine, f=fine, m=medium, c=coarse, gr=granular, sbk=subangular blocky, abk=angular blocky, pl=platy, pr=prismatic, m=massive. The slash between two structural at- tributes stands for larger aggregates parting to smaller ones. not found in pedon 3 within 170 cm of the soil surface. Pedons 4–8, which are further away from the major bedrock highs, did not have a sandy topsoil and they were composed of lacus- trine materials with no glacial till within the in- vestigated depth. Pedon 4 had an 11-cm stratum of sandy shore deposit. This is likely the result of its close proximity to a minor bedrock high area. The different surfaces in this landscape have highly variable textural properties. Nearly all pedons had lithological discontinuities, i.e. ho- rizons were composed of materials of different origins. There appears to be two clayey lacus- trine materials; one has 40 to 70% clay and the other more than 70% clay. The lacustrine mate- rials in pedons 2, 3, 4 and 7 and the upper parts of pedons 6 and 8 were the coarser material and those in the lower parts of pedons 4 and 7 were the finer material. This reflects the different depths of water during deposition. Currents in shallower waters have more energy and a great- er capacity to move coarser particles. The clay in the investigated pedons was not varved, indi- cating that the studied horizons had been depos- ited after the retreat of the continental ice sheet. No slickensides or pressure faces (signs of pe- doturbation) were found. Soil forming processes Pedon 1 at an elevation of 30 m emerged from water during late Ancylus or early Littorina pe- riod about 7000 BP. It is well drained; no water table was encountered during sampling. Owing to coarse texture and the litter from the vegeta- 297 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 291–302. Table 2. Selected physical and chemical properties of pedons in Helsinki. Soil pH values marked with an asterisk (*) represent fresh pH, and, in the parentheses, a pH after eight weeks of aerobic incubation. Other pH values were measured in samples dried as usual. P was extracted with 1% citric acid. Clay stands for particles <0.002 mm, silt for 0.002–0.06 mm and sand for 0.06–2 mm. Horizon Particle size distribution Base Org. P >2mm sand silt clay pH saturation. C ————————%———————— % % mg kg-1 Helsinki 1 Oa n.d. n.d. n.d. n.d. 3.8 11 43.1 73 E 12 87 11 3 3.5 9 1.1 7 Bs 29 92 5 3 4.6 15 0.9 21 BC 6 74 23 3 4.7 12 0.3 23 C 15 73 24 3 5.1 11 0.1 64 Helsinki 2 Ap 4 68 16 16 6.0 75 4.9 470 Bw 6 84 6 10 5.5 55 0.6 2Bg 0 13 20 67 5.3 67 0.7 3Cg1 0 15 80 5 5.8 68 0.1 4Cg2 2 58 39 3 5.8 67 0.1 Helsinki 3 Ap 1 72 17 11 6.4 81 2.7 310 E 0 76 21 3 6.4 57 0.3 Eg 0 76 21 3 6.4 55 0.2 Bg 0 62 24 14 6.7 85 1.9 Cg1 0 57 28 15 6.8 80 1.5 2Cg2 0 22 44 34 6.8 86 0.2 3Cg3 0 9 25 66 6.8 91 0.4 Helsinki 4 Ap 3 14 48 38 6.2 82 3.9 346 Bg1 0 7 37 56 4.9 42 2.4 Bg2 1 18 33 49 4.8 41 1.5 2Cg1 0 68 23 9 5.2 78 0.2 3Cg2 1 4 39 57 6.2 86 0.3 Helsinki 6 Ap 0 18 41 41 6.2 83 3.7 619 Bg1 0 16 40 44 5.0 65 0.7 Bg2 0 4 53 43 5.2 75 0.4 BC 0 3 13 84 4.4 76 0.6 C 0 2 12 86 5.8 90 0.4 Helsinki 7 Ap 0 8 45 47 6.2* 70 4.8 214 Bg1 0 3 39 58 4.4* 23 2.4 Bg2 0 3 32 65 4.0(3.9)* 18 1.8 Bj 0 4 29 67 3.8(3.9)* 16 1.9 Cg 0 5 28 67 3.55(3.4)* 18 3.0 C 0 3 32 65 6.5(2.9)* 63 3.2 Helsinki 8 Oi 4.7* 61 16.7 151 Bg1 0 32 45 23 7.1(3.0)* 52 1.6 205 Bg2 0 6 39 55 7.2(4.3)* 92 0.5 305 C1 0 1 12 87 7.3(6.1)* 96 0.7 374 C2 0 3 18 79 7.2(6.7)* 100 0.5 376 298 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Mokma, D.L. et al. Soils of coastal Finland tion dominated by Scotch pine, translocation of C, Al, and Fe was evident by the presence of a grayish colored (7.5YR 5/2) continuous albic E horizon with no redoximorphic features and a reddish colored (7.5YR 4/4) spodic Bs horizon (Table 1). Spodic materials were identified from the color, pH, and organic C content. In the Bs horizon the index of accumulation of Fe and Al (0.5•Fe ox + Al ox ) was 0.43% but it is likely that in the upper part of the Bs horizon the index would be higher. The index for the E horizon was only 0.067%, indicating marked depletion of Fe and Al. Our interpretation is that pedon 1 is a weakly developed Spodosol/Podzol (Ta- ble 3). Soil forming processes began altering the materials in pedon 2 about 3600 years ago (Ta- ble 1), in pedon 3 about 1800 years ago, and in pedons 4–8 less than 1000 years ago. The ma- jor processes were the addition of organic mat- ter from the vegetation growing on the site and the reduction of Fe because of the anaerobic en- vironment. The intensity of other soil forming processes is likely dependent upon the effective- ness of the drainage system and they have prob- ably been more active since artificial drainage was gradually intensified less than 150 years ago. The six pedons in the cultivated area had naturally high water tables and are somewhat poorly or poorly drained, as evidenced by the redoximorphic features (redox depletions and concentrations) above 50 cm (Table 1). When these pedons were described and sampled, the water tables were at depths of 63–162 cm. The high water tables are attributable to the cool and humid climate, low elevation, and proximity to the sea. Water also enters the cultivated soils as lateral flow from the surrounding bedrock high areas, and the clayey subsoil of these pedons inhibits vertical water movement. All cultivated soils had cambic B horizons, owing to the development of structure and pro- nounced redoximorphic features. These features formed quickly after the soils were artificially drained. The Bg1 horizon in pedon 7 (emerged from water 325 BP and drained about 70 years ago) had a strong grade of blocky structure, sta- bilized by thick coatings of iron (hydr)oxides (Table 1). The BC horizon of pedon 6 (100 BP and drained for 70 to 90 years) had redox con- centrations and strong prismatic structure part- ing to moderate angular blocky aggregates. In comparison, the C horizons of pedons 6 and 7 were structureless (massive) with no redox con- centrations. The C horizons were greater than 1 meter below the soil surface, the approximate depth of the drainage tile. The Bg and Cg1 hori- zons of pedon 8 had a weak grade of structure, a chroma of 1 and no redox concentrations and the Cg2 horizon was massive. The area in which pedon 8 is located has not been artificially drained and has not been used even for pasture and therefore represents the soil in its native state. From these findings it can be concluded that subangular blocky structure and continuous, thick coatings of iron (hydr)oxides formed in the Table 3. Classification of the investigated pedons according to Soil Taxonomy (Soil Survey Staff 1998), FAO-Unesco system (FAO 1988) and Word Reference Base for Soil Resources (WRB) system (FAO 1998). Pedon Soil Taxonomy FAO–Unesco WRB 1 Typic Haplocryod Haplic Podzol Haplic Podzol 2 Aquic Haplocryoll Eutric Cambisol Gleyic Phaeozem/Mollic Gleysol 3 Aquic Haplocryoll Eutric Cambisol Gleyic Phaeozem/Mollic Gleysol 4 Typic Cryaquept Dystric Cambisol Dystric Cambisol 5 Typic Cryaquoll Eutric Cambisol Gleyic Phaeozem/Mollic Gleysol 6 Aquic Haplocryoll Gleyic Cambisol Gleyic Phaeozem 7 Sulfic Cryaquept Thionic Gleysol Hyperdystric Gleysol 8 Histic Sulfaquent Thionic Gleysol Protothionic Gleysol 299 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 291–302. horizons above the drainage tile in less than 70 years. An earlier study (Yli-Halla and Mokma 1999) on soil pH before and after aerobic incubation indicate that pedons 7 and 8 had sulfidic materi- als. This was confirmed in the present study by the analyses of total and sulphate sulphur (Table 4). In pedon 8, which is commonly water-logged, sulfidic materials occurred at 25–42 cm imme- diately below the histic epipedon but the lower horizons were nonsulfidic. Sulphate is available in the brackish sea water and energy for the mi- crobial reduction is provided by the organic matter from the grassy and reedy vegetation. These results suggest that sulfidic materials are currently accumulating on the coast of the Gulf of Finland. Sulfidic materials were also present in pedon 7 (below 117 cm) where they likely originated from the Littorina period during which most sulfidic sediments were deposited in Fin- land. The upper horizons in pedon 7 were oxi- d i z e d a n d h a d t h i c k c o a t i n g s o f i r o n (hydr)oxides. Some light colored mottles (2.5Y 6/4) in the Bj horizon suggest the presence of jarosite, a mineral typical of acid sulfate soils but the pH and sulphate content of these hori- zons was, however, marginal to meet the crite- ria for a sulfuric horizon. Mollic plow layers and gleyic properties One of the criteria of a mollic epipedon in Soil Taxonomy and the FAO-Unesco system is the P content of the soil which must not exceed given limits. The levels of P extractable with citric acid in Ap horizons vary from 214 to 619 mg kg-1 (P 2 O 5 491 from 1420 mg kg-1) (Table 2). All levels were less than the new criterion (654 mg P kg-1, i.e. 1500 ppm P 2 O 5 , Soil Survey Staff 1999) but greater than the criterion of the FAO- Unesco system and the criterion of Soil Taxono- my applied until 1998 (109 mg P kg-1, i.e. 250 ppm P 2 O 5 , Soil Survey Staff 1975, FAO 1988). The P originates from manure and fertilizers and from the parent material. In five topsoil samples of the fields of the Viikki area, included in the study of Hartikainen (1979), there was on aver- age 260 mg P kg-1 in apatitic form, indicating the young age of the soil. Apatitic P is dissolved with acidic solutions, e.g. sulphuric acid (Chang and Jackson 1957) and acid (pH 3.0) oxalate (Uusitalo and Tuhkanen 2000). Particularly on the basis of the results of citric acid extractable P in the subsoil of the non-cultivated pedon 8, we can assume that citric acid also dissolves native P and may not be suitable for identifying anthropogenic P inputs in soils rich in apatitic P. Furthermore, when the fields of the research farm had been tested in 1999, the P concentrations extracted from the Ap horizons with an acid ammonium acetate solution ranged from 10.1 to 17.0 mg dm-3 of soil in samples collected around pedons 2, 4, 6, and 7 (the field around pedon 3 was not tested). According to the seven-step clas- sification used in soil testing in Finland, none of the values was ‘high’ or ‘excessive’, showing that the soils are not overly enriched with an- thropogenic P inputs. The moist colors (Table 1) of the Ap hori- zons of the cultivated soils were all dark enough to meet the moist color requirement of the mol- lic epipedon (FAO 1988 and 1998, Soil Survey Staff 1999). However, the dry colors of pedons 4 and 7 were too light (value of 6 rather than 5). The thickness of the Ap horizon was great Table 4. Contents of total and sulfate sulfur in selected ho- rizons of two acid sulfate soils of the Viikki landscape. Sulfate sulfur was determined after eight weeks of aerobic incubation. Pedon and horizon Total S, mg kg-1 SO 4 -S, mg kg-1 Helsinki 7 Bg2 1400 94 Bj 2200 113 Cg 4400 497 C 17500 4820 Helsinki 8 Bg1 10700 7590 Bg2 8900 1220 C1 2500 690 C2 1100 244 300 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Mokma, D.L. et al. Soils of coastal Finland enough and the base saturation was high enough to meet the Mollisol requirement of Soil Taxon- omy in pedons 2, 3 and 6. The ochric epipedons and low base saturation excluded pedons 4 and 7 from being Mollisols. Pedon 5 was considered to have a mollic epipedon on the basis of color, even though it was not chemically analysed. The occurrence of soils formally meeting the crite- ria of Mollisols has not been systematically sur- veyed in Finland but mollic epipedons seem to occur mostly in cultivated soils which have sandy plow layers (Yli-Halla et al. 2000). A sim- ilar observation has been made in Denmark (Greve et al. 2000). In the FAO-Unesco system, most cultivated soils of this landscape are Cambisols (Table 3). Even though they are rather poorly drained, they don’t usually meet the requirements of gleyic properties and thus, only few can be classified as Gleysols. The ones showing the mollic colors are excluded from Phaeozems by the high P con- tent. In the WRB system, the gleyic color pat- tern was defined (FAO 1998). This pattern was identified within 50 cm of soil surface in pedons 2, 3, 5, 7 and 8 which thus, were classified as Gleysols. The gleyic colors may, however, re- flect the wetness of earlier times. Over time, ar- tificial drainage and isostatic land uplift promote aeration and make the matrix colors redder, ren- dering the gleyic properties less pronounced. For many of these soils, Phaeozem is presented as an alternative name (Table 3) in the WRB sys- tem where the P content is not a criterion of this soil unit. In the WRB system, sulfidic materials which are deeper than 1 m are not taken into account while in the FAO-Unesco system they are recognized within 125 cm of soil surface. Thus, pedon 7 doesn’t get the thionic attribute in the WRB system. Pedogenesis and man Man has profoundly influenced the present ag- ricultural soils at least by drainage, tillage, lim- ing, fertilization and manuring. Drainage has promoted oxidizing conditions of the soil pro- file and contributed to increased redox concen- trations and to the formation of structure, the two characteristics from which the cambic horizon was identified. Therefore, it can be assumed that the cambic horizon in these low-lying soils is at least partialy a result of human activity. When classifying according to Soil Taxono- my (Soil Survey Staff 1998), Mollisols domi- nate the cultivated land of this landscape, Incep- tisols being second in frequency (Table 3). In their origin, Mollisols of the present landscape deviate strongly from the original concept of Mollisols (soils formed under native grassland). It is probable that the organic C in the subsoils originated mostly from the high biological ac- tivity during the deposition of the lacustrine material, not from recent biological activity in the soil profile. Furthermore, there is an abrupt decrease of organic C content in these soils be- tween the Ap and the horizon below. This fea- ture is caused by additions of organic matter as crop residues and animal manures and mixing of the plow layer annually. Possibly some, may- be most, of the cultivated soils of this landscape have, in the native state, had a histic epipedon similar to that of pedon 8. When reclaimed for agriculture, drainage accelerated the rate of de- composition of the organic matter and tillage mixed the organic materials into the plow layer. The high base saturation of the Ap horizon was at least partially caused by liming, not by cal- careous parent materials, and without liming the epipedon might be umbric. It is impossible to find a native soil equiva- lent to the cultivated ones in this landscape be- cause all lacustrine sediments at the same ele- vations have been reclaimed for agriculture. In addition, the native areas are glacial till in the bedrock high areas and very low-lying soils be- tween the cultivated land and the sea. Therefore it is impossible to check the occurrence of a cam- bic horizon, a mollic epipedon, or gleyic prop- erties in the native state at the same elevation as the present culvivated soils of this landscape. It can, however, be assumed that in the native state the base saturation of the epipedons would be lower. Without artificial drainage, the cambic 301 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 291–302. horizons would also be less developed or absent and gleyic properties would be more pronounced, resulting in the soils being classified as Entisols (Soil Taxonomy) or Gleysols (FAO and WRB). Conclusions In this landscape, a catena of Spodosols, Mol- lisols, Inceptisols, and Entisols of Soil Taxono- my was identified. According to the FAO-Unesco system, the catena consists of Podzols, Cam- bisols, and Gleysols while according to the WRB system Phaeozems are also included. It needs to be pointed out that the mollic epipedons had the highest color value and chroma allowed, while in the ochric epipedons the color was borderline to the mollic epipedon. This is problematic since the mollic epipedon is one of the strongest char- acteristics influencing classification. It was also difficult to differentiate between the cultivated Cambisols and Gleysols of the WRB system. Thus, soils which differ from one another only marginally get different names at the highest lev- el of classification. This lability, which is a po- tential source of inconsistent soil classification, can be attributed to the young age and weak de- velopment of the pedogenic features and to the varied impact of man on soil properties, not only in plow layers but also in subsoils down to the drainage depth. Conclusions about the native state of the soil, and about the further develop- ment upon termination of human impact, are quite uncertain. Therefore it is difficult to fol- low the principle that “short-term management effects should not influence soil grouping” (FAO 1998, p. 11). More discussion is needed about the classification of these young soils, particu- larly on how the different effects of human in- fluence should or shouldn’t be taken into ac- count. References Aaltonen, V.T. 1941. Zur Stratigraphie des Podsolprofils, besonders vom Standpunkt der Bodenfurchtbarkeit. III. Communicationes Instituti Forestalis Fenniae. 29, 7. Chang, S.C. & Jackson, M.L. 1957. Fractionation of soil phosphorus. Soil Science 84: 133–134. Elonen, P. 1970. Particle size analysis of soil. Acta Agralia Fennica 122: 1–122. Eronen, M., Glückert, G., van de Plassche, O., van der Plicht, J. & Rantala, P. 1995. Land uplift in the Olkiluo- to-Pyhäjärvi area, southwestern Finland, during the last 8000 years. Report YJT-95–17. 22 p. Voimayh- tiöiden Ydinjätetoimikunta, Helsinki. European Soil Bureau 1998. The soil geographical data- base of Europe at scale 1:1 000 000. INRA, Orleans, France. FAO 1988. FAO-Unesco soil map of the world. Revised Legend. World Resources Report 60. FAO, Rome. Reprinted as Technical Paper 20, International Soil Reference and Information Centre, Wageningen. 144 p. – 1998. World Reference Base for Soil Resources. World Soil Resources Report 84. FAO, Rome. 88 p. Giesler, R., Ilvesniemi, H., Nyberg, L., Hees, P. van, Starr, M., Bishop, K., Kareinen, T. & Lundström, U.S. 2000. Distribution and mobilization of Al, Fe and Si in three podzolic soil profiles in relation to the humus layer. Geoderma 94: 249–263. Greve, M.H., Yli-Halla, M., Nyborg, Å.A. & Öborn, I. 2000. Apprisal of World Reference Base for Soil Resources – from a Nordic point of view. Danish Journal of Ge- o g r a p h y 1 0 0 : 1 5 – 2 6 . Hartikainen, H. 1979. Phosphorous and its reactions in terrestrial soils and lake sediments. Journal of the Scientific Agricultural Society of Finland 51: 537–625. Hyyppä, E. 1950. Helsingin ympäristö. Maaperäkartan selitys. Geologinen Tutkimuslaitos. 53 p. Mount, H.R., Newton, D.L., Räisänen, M.-L. & Lee, S.E. 1995. Morphology of the soils in Central Finland. Soil Survey Horizons 36: 142–154. Rasmussen, K., Sippola, J., Urvas, L., Låg, J. & Troeds- son, T. 1989. Soil map of Denmark, Finland, Norway and Sweden 1:2 000 000. Landbruksforlaget, Oslo, Norway. Righi, D., Räisänen, M.-L. & Gillot, F. 1997. Clay mineral transformations in podzolized tills in central Finland. Clay Minerals 32: 531–544. Seppä, H. & Tikkanen, M. 1998. The isolation of Kruunu- vuorenlampi, southern Finland, and implications for Holocene shore displacement models of the Finnish south coast. Journal of Paleolimnology 19: 385–398. Soil Survey Staff 1975. Soil Taxonomy: A basic system of soil classification for making and interpreting soil surveys. USDA-SCS Agricultural Handbook 436. US 302 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Mokma, D.L. et al. Soils of coastal Finland Government Printing Office, Washington, DC, USA. – 1993. Soil Survey Manual. 2nd ed. USDA-SCS Agri- cultural Handbook 18. US Government Printing Of- fice, Washington, DC, USA. – 1998. Keys to Soil Taxonomy. 8th ed. US Govern- ment Printing Office, Washington D.C., USA. – 1999. Soil Taxonomy: A basic system of soil classifi- cation for making and interpreting soil surveys. 2nd ed. USDA-SCS Agricultural Handbook 436. US Gov- ernment Printing Office, Washington, DC, USA. Taipale, K. & Saarnisto, M. 1991. Tulivuorista jääkausiin. Suomen maankamaran kehitys. WSOY. Porvoo. 416 p. Uusitalo, R. & Tuhkanen, H.-R. 2000. Phosphorous sat- uration of Finnish soils: evaluating an easy oxalate extraction method. Agricultural and Food Science in Finland 9: 61–70. Vuorinen, J. & Mäkitie, O. 1955. The method of soil test- ing in use in Finland. Agrogeological publications 63: 1–14. Yli-Halla, M. & Mokma, D.L. 1998. Soil temperature re- gimes in Finland. Agricultural and Food Science in Finland 7: 507–512. – & Mokma, D.L. 1999. Classification of soils of Fin- land according to Soil Taxonomy. Soil Survey Hori- zons 40: 59–69. – , Mokma, D.L., Peltovuori, T. & Sippola, J. 2000. Suomalaisia maaprofiileja. Summary: Agricultural soil profiles and their classification. Publications of Agri- cultural Research Centre of Finland. Series A. 103 p. SELOSTUS Nuoria maita Viikin pelloilla Delbert L. Mokma, Markku Yli-Halla ja Helinä Hartikainen Michiganin osavaltion yliopisto, USA, Maatalouden tutkimuskeskus ja Helsingin yliopisto Helsingin yliopiston Viikin opetus- ja tutkimustilan pelloilla, niiden vieressä olevalla moreenialueella ja meren äärellä olevassa ruovikossa tutkittiin kahdek- san maaprofiilia n. 1,5 metrin syvyyteen ja niissä esiintyvät maannostumisen merkit kuvailtiin. Maan- nokset nimettiin amerikkalaisen Soil Taxonomy -jär- jestelmän, FAOn-Unescon järjestelmän ja vuonna 1998 julkaistun World Reference Base for Soil Resources (WRB) -järjestelmän mukaan. Maannos- ten suhdetta niiden sijaintiin maastossa luonnehdit- tiin. Moreenialue, joka on paljastunut merestä noin 7000 vuotta sitten, oli heikosti podsoloitunutta maa- ta. Viljelyalueen korkeimmat kohdat ovat paljastuneet merestä 2000–3000 vuotta sitten. Näiden maiden pin- takerros on karkeaa hietaa, joka on kulkeutunut ve- den vaikutuksesta läheisiltä moreeni- ja avokallio- alueilta, ja hiedan alla on savea. Viljelyalueen keskiosis- sa, jotka ovat nousseet merenpinnan yläpuolelle alle 1000 vuotta sitten, koko tutkittu maprofiili on savea. Kaikissa viljelymaissa oli tumma mollic-horisontti tai hieman vaaleampi ochric-horisontti. Syvemmällä niissä oli cambic-horisontti, jonka tuntomerkkejä oli- vat rautahydroksidilaikut ja maahan kehittynyt raken- ne. Lähimpänä merta esiintyi happamia sulfaattimai- ta, joiden veden kyllästämissä horisonteissa oli sul- fidia. On todennäköistä, että ojitus on merkittävästi edistänyt rakenteen kehittymistä Viikin alueen vilje- lymaissa, jotka ovat luontaisesti märkiä. Viljelymaat kuuluivat Soil Taxonomy -järjestelmän Mollisol- ja Inceptisol-luokkiin, FAOn-Unescon järjestelmän Cambisol- ja Gleysol-luokkaan ja WRB-järjestelmän Phaeozem-, Cambisol- ja Gleysol-luokkiin. Soils in a young landscape on the coast of southern Finland Introduction Material and methods Results and discussion Conclusions References SELOSTUS