4. Bog and Peat soils.

Hydromorphic soils characterized by an excess of soil moisture are widespread in the Polissya zone. Gleying is beleived in this country to the first stage of any swamps formation. The next stage is the formation of peat. Organic (peat) soils occupy anarea of 0.94 mln ha within the lower levels of the terraces, on the bottom lands of ancient river valleys and within the locked depressions of topography so numerous on the Polissian lowland.

Sedimentary peats usually accumulating in depression with high water table are dominant in the Polissya. Upland peats formed in excessive wetness caused by precipitation are a rarity occurring only in the north-western part of the zone. Below is the description of a lowland solonchaky (saline from the very surface) peat soil encountered near Shostka (Sumy region), within the Shostka (river) floodplain:

T₁Hks 0-20 cm: surface horizon, dark brown,well decomposed and humified peat, thickly interlaced with grass roots, crumby, calcareous, saline; transition to the next horizon is more or less clear.

T₂hks 20-55 cm: moderately decomposed peat layer, calcareous, saline, well dividing into platy fragments, rich in shells; occasional viviamite accumulations rusty-brown films on the surface fragments; gradual transition to the next horizon.

T₃(h)ks 55-160 cm: slightly decomposed layer of peat; calcareous, saline, with residues of sedges and rashes, abundant mollusk shells, iron oxide films on the cleavage plains of horizon plates; sharp transition to the next (mineral) horizon.

D 160-290 cm and deeper whitish dull grey meadow marl.

Productive use of peat soils is possible only after their drainage which is not always desirable. A profound soil amelioration is needed after the drainage, but then it is possible to employ such soils for the production of hay and as pastures with controlled grazing. Perennial grasses, forage crops, potatoes, corn for silage, small grains and flax (on base unsaturated variant) can be grown on drained peat soils.

Organic deposits are generally classified on the basis of their state of decomposition. Those deposits that are slightly decayed are termed PEAT, while those that are markedly decomposed are called MUCK.

Muck is generally decomposed to the point where the original plant parts cannot be identified.

5. Practices of soil management in Ukrainian Polissya.

Soddy podzolic soils are poor in nutrient elements. Their OM content is low and so is their CEC. Their adsorbing complex is poorly saturated with bases. To neutralize the excessive acidity the soils should be regularly limed. The rate form manure should be no less than 15 mt/ha of a crop rotation. Sandy soils formed in alluvial deposits are subjected to soil erosion by wind. They must not be left without proper residue cover. While liming podzolic soils it is necessary to keep in mind that they may be deficient not only in calcium but in magnesium too. On some acid soils of heavier texture and greater values of hydrolytic acidity phosphorite meal may prove more effective than superphosphate. Many soils may favor the application of loess or clay, provided there is an economic feasibility of the practice.

Gleyed soils need drainage if it is economically feasible. But some of them are better to be used for the production of moisture-loving crops such as flax or vegetables. They should not be used for orchards.

Ukrainian rendzinas (soddy carbonatic soils) are no good for flax and hemp, as well as orchards and vineyards. Sugar beet feels good on such soils. Some acidic forms of mineral fertilizers are needed on them.

Even the small rates of sodium chloride may be effective on such soils. A deep plowing is recommended for the rendzinas. If improves the conditions favoring weathering and disintegration of a solid rock.

All Polissian soils need a deeper plow layer. But the process of deepening it should be gradual enough not to allow the appearances on the surface of the elluvial horizon which is acid and with poor fertility and physical properties.

Peat soils are very deficient in potassium and the microelement of copper.

LECTURE TWELVE.

Soils of the Forest-Steppe and Chernozemic Steppe Zones of Ukraine.

Study outline:

1. Natural Features and Pedogenic Factors.

2. Grey Forest and Podzolized soils.

3. Chernozems of the Steppe Zone.

1. Natural Features and Pedogenic Factors.

The Forest-Steppe zone of Ukraine occupying an area of about 20mlm ha is the most favorable region for agriculture. The climate is slightly warmer and milder than in the Forest zone. Humidity coefficient is very close to unity, which means that the annual amount of precipitation and that of evaporation from an open water surface are approximately equal to each other. The western regions of the Forest-Steppe zone are more moist and humid, while the eastern ones are more arid and continental in climate. Thus the Poltava region may be deficient in moisture to the extent limiting in some years the yields of field crops.

The Forest-Steppe zone differs from the Polissya by the wider areas of the Steppe vegetation: grasslands and meadows. These areas alternate here with oak, oak-hornbeam, and oak-maple-lime forests. Humid-steppe grass associations dominate in the north, while more xerophytic grass associations appear in the south.

Parent materials of the Forest-Steppe zone are characterized by a kind of “lithologic uniformity” being represented by the loesses and loess-like loams. Only on floodplains and the terraces of the river valleys the alluvial deposits serving the parent materials of soils are mainly sands and loamy sands. On eroded slopes they may be represented by the red-brown and other clays and some other deposits the total area of which is very small.

The loess on the terraces is, as a rule, saline to a varying extent. In the northern half of the zone the loess is dominantly light and medium loam with a high content of coarse silt fraction (0.01- 0.05mm). The soils formed in it are very prone to gullying. Further to the south the loess becomes heavier in texture, so that on the border with the Steppe it may be clay-loam and even clay. The dominant soils are typical, podzolized, leached and regraded (repeatedly saturated podzolized) chernozems.

These soils occupy an area of about 13mln ha. The rest of the zone is covered mostly by podzolized and grey forest soils.

Forest-Steppe zone is the region of active water and wind erosion.

Chernozemic steppe zone is divided from the Forest-Steppe zone by the isoline of annual amount of precipitation within 450-500mm. To the south and west the amount of precipitation decreases, so that on the Sivash coast it is within 310-320mm. Chernozemic and Arid Steppe zones are “the holders” of the greatest amount of heat resources in Ukraine. Thus the sum of temperature over +5⁰C in the north is 3200⁰C and on the south 3800-4000⁰C, whereas in the Forest-Steppe zone this characteristic fluctuates within 2900-3100⁰C.

Topography in the zone of Steppe is dominantly plainland but nonuniform in both genetic and structural respect. The Near-Black-Sea Lowland in the south gradually turns into a number of uplands (150-300m above sea level): Bessarabian, Podilska, Pridniprovska. Further to the north-east there is a Donetsky Highland (with the highest point being 367m above sea level).

Loesses are the dominant parent materials in the Steppe zone. They cover the watershed plateaus and the ancient terraces of the river valleys. They are mostly clay loams and loamy clays. Non-loess parent materials are widespread on Donetsky Highland. They are represented by sandstone, shales (schists), chalky-marls, limestones and clays. In the floodplains of the river valleys the parent materials of soils are represented by the alluvial deposits of varying texture but mostly sands.

On the watershed plateaus the depth of water table is within 5-10m and the ground waters do not affect soil formation in any way. But in the podas (saucer-like depressions in the Southern Chernozemic and Arid Steppes) the ground waters are only 2-3m deep and they cause the gleying processes in soil profiles. Ground waters are saline with sulfate and chloride salinity.

Ordinary chernozems occupying an area of 10.4mln ha are the dominant Chernozemic Steppe soils. Southern chernozems of the southern subzone developed under more arid conditions. Their profiles are shorter and OM content lower than those of the ordinary chernozems and besides they are more salinity and sodicity affected.

The geography of the soil cover is closely connected with that of vegetation. The natural vegetation of the Northern Steppe is composed of meadow, fescue, and needle grasses. Various species of a feather grass are encountered all over the Ukrainian Steppe on very small plots preserved from plowing, which are becoming a rarity. To the south, the participation of xerophytic and halophytic species becomes greater. On the rocky soils of Donetsky Highland wormwood and petrophytes dominate in thinned – out grass stands.