- •Department of Soil Science & Soil Conservation
- •Introduction
- •2. General scheme & processes of soil formation.
- •3. Morphological features of the soil profile.
- •4. Soil ecology.
- •Study outline:
- •1. Soil definition and the factors of plant growth.
- •2. Plant roots and soil relations.
- •3. Soil fertility and soil productivity.
- •4. Soil texture.
- •1. Sources and composition of som.
- •2. Residue decomposition and humus formation.
- •3. Agronomical and ecological roles of som.
- •4. Maintenance and balance of som.
- •2. Nature and properties of soil colloids.
- •3. Pole in soil genesis and soil productivity development.
- •4. Types and practical significance of soil absorbing capacity.
- •2. Soil Properties as Effected by Exchangeable Cations.
- •3. Soil Acidity & Acid Soil Amendment.
- •4.Soil Alkalinity & Sodic Soil Amendment.
- •5. Soil Buffer Capacity & Significance of Soil pH.
- •2. Managing soil structure.
- •3. Particle density and bulk density.
- •4. Soil porosity and aeration porosity.
- •5. Mechanical properties of mineral soils and their management.
- •2. Soil Water Movement.
- •3. Plant and Soil Water Relations.
- •4.Soil Water Regime.
- •6. Soil Water Management.
- •1.1. Composition and concentration of soil solution.
- •1.2. Osmotic pressure of soil solution.
- •1.3. Redox potential and redox processes in the soils.
- •2. Soil air, a gaseous phase of the soil.
- •2.1. Soil air composition and properties.
- •2.2. Plant requirements to soil aeration.
- •3. Management of soil redox and aeration regimes.
- •1. Soil temperature & modes of energy transfer.
- •2. Conduction of heat in soil. Heat-related soil properties.
- •3. Thermal conductivity of soil.
- •4. Thermal regime of soil profiles &its control.
- •2. Principles of soil cover zoning in Ukraine.
- •3. Soil Zoning in the Mountain regions.
- •4. Fao nomenclature of soils.
- •2. Soddy Podzolic and Soddy Podzolic Gleyed soils.
- •3. Soddy soils.
- •4. Bog and Peat soils.
- •5. Practices of soil management in Ukrainian Polissya.
- •2. Grey Forest and Podzolized soils.
- •3.Chernozems of the Steppe Zone.
- •2. Dark chestnut and chestnut soils.
- •3. Salt-affected soils.
- •4. Practices of soil amendment and land use improvement in the arid steppe zone.
3.Chernozems of the Steppe Zone.
Typical and leached chernozems are the most widespread soils in the Forest-Steppe zone. Typical chernozems rightly deserve to be called the soils of maximum productivity. Two important soil species within this subtype are (1) typical chernozems with low OM content and (2) typical chernozems with moderate OM content. Typical chernozems with low OM content formed dominantly in loess occupy a total area of 4.8 mln ha, 4.5 mln ha being within the plowland. The soils are widespread on the plateaus between the river valleys and the terraces. The soil below was described and photographed for the Atlas of Ukrainian Soils at the Sumy agricultural experiment station.
Hk 0-41 cm: surface horizon of OM accumulation; dark grey, heavy loam with coarse silt separate domination; 0-27 cm: a plow layer, powdery with clods, loose; 27-41 cm: carbonate-containing, granulated with clods, compacted, transition gradual.
Hpk 41-70 cm: upper transitive horizon; well but nonuniformly “humusified”, effervescent with 10% HCl, dark grey with brownish tint, moderate loam with coarse silt domination; grainy and cloddy in structure, loose with friable clods, carbonatic “mold” on the “walls” of earthworm channels, transition gradual.
Phk 70-120 cm: lower transitive horizon; nonuniformly colored with organic matter, carbonatic, grey-brown, moderate loam with coarse silt domination, cloddy with friable clods, many crotovinas and earthworm channels with carbonate “mold”. Transition gradual.
P(h)k 120-203 cm: loess transitive to parent material; mottly with numerous crotovinas, greish-brown, moderate loam, cloddy, loose from mole-mode channels, rich in carbonate “mold”.
Pk 203-220 cm: parent material, dull yellow, moderate loam with abundant carbonate “mold”.
The soils like this respond well to the application of organic manures and mineral fertilizers, especially phosphorus and nitrogen ones. Their need in K2O is insignificant. Typical chernozems with moderate OM content have a similar profile description, but their OM content in the surface horizon exceeds 5.5%. These chernozems occupy a total area of about 1.4 mln ha, 1.2 mln ha being a plowland. Soil characteristics of a pedon described in the Atlass of Ukrainian Soils are as follows: OM=8.61%; Cha/Cfa=1.53; pHH2O=6.7; S=40 meq/100g; Hh=1.19; dv=1.13 g/cm3; D=2.62 g/cm3; TP=57%; aeration of FC=12.9%V; WC=16.9%; Total N=0.27%; Total P2O5=1471 (0.147); Total K2O=24052 ppm (2.4%); exchangeable K2O=166 ppm.
Ordinary and Southern chernozems are subzonal subtype of Northern and Southern subzones respectively of the Chernozemic Steppe zone. Ordinary chernozems with moderate OM content have the following profile description:
H 0-48 cm: surface horizon of OM accumulation; dark grey, light clay, 0-28 cm: plow layer, powdery with clods, loose; below plow layer: grainy with numerous earthworm channels and rare crotovinas; transition gradual.
Hp/k 48-80 cm: upper transitive horizon, well humusified, dark brown with brownish tint, light clay, cloddy-granulated, compacted, porous, numerous earthworm channels and casts, occasional crotovinas; carbonate mold in the lower half of the horizon; effervescence from 10% HCl below the depth of 62 cm; transition gradual.
Phk 80-110 cm: lower transitive horizon; dark brown, light clay, with clods, grains and nuts among soil aggregates, compacted with numerous channels of moles and rodents and abundant carbonate mold. Transition gradual.
Pk 110-180 cm: parent material; dull yellow, light clay, mottly from the crotovinas in the upper part. Carbonate concretions (byeloglaska, “white eyes”) occurs from the depth of 140 cm. On another soil profile the layer of maximal carbonate concretion accumulation was within 107-160 cm. Beside byeloglazka the horizon of parent material may be rich in carbonate “micellium”
Southern chernozems formed in loess occupy a total area of 3.5 mln ha, of which 3.1 mln ha belong to the plowland. The soils cover flat watershed plateaus. One of their characteristic features is the layer of gypsum and soluble salts within the depths of 220-320 cm of a parent material.
Soluble salts are represented mainly by sodium sulfate and to a less extent – by sodium chloride. Below is a description of southern chernozems near the village of Podove, Kherson region.
H 0-25 cm: surface horizon of OM accumulation, plow layer; dark grey, light clay, powdery with friable clods, loose; transition distinct.
Hp (i) 25-37 cm: upper transitive horizon; dark grey with brownish tint, light clay; soil aggregates presented by clods, grains and nuts; compacted; transition gradual.
Phi/k 37-53 cm: lower transitive horizon; dark brown, light clay, cloddy-prismatic, compacted, porous, effervescent from 10% HCl below the depth of 45 cm; transition gradual.
P(h)k 53-85 cm: loess with some streaks of humus-containing material; dull yellow with brownish tint, abundant carbonate concretions, light clay, compacted, cloddy; transition gradual.
Pk 85-180 cm: parent material; dull yellow loess; light clay, porous, divided into large clods, compacted. Southern chernozems are less productive compared with ordinary ones. Some say, the aridity of climate is the reason. The soils are “responsive” to the application of organic manures and mineral fertilizers, especially if irrigated. The described pedon contains 3.1% of OM in the surface horizon. pHH2O=6.9; pHKCl=6.2; CEC=36.44 meq/100g; dv=1 g/cm3; D=2.6 g/cm3; TP=61.6 %V; WC=11%m; FC=31.9m; Aeration porosity at FC=29.7%V. Total K2O= more than enough, but exchangeable K2O is within 120-180 ppm; Total N=0.16%; Total P2O5=0.13%. Irrigation is necessity to obtain economically feasible yields of field crops.
LECTURE THIRTEEN.
Soils of the Arid Steppe Zone.
Salt Affected Soils.
Study outline:
Natural features and pedogenic factors.
Dark chestnut and chestnut soils.
Salt-affected soils.
Practices of soil amendment and land use improvement in the arid steppe zone.
1. Natural features and pedogenic factors.
Total area of arid steppe zone is about 4,7 mln. ha. the zone lies within the southernmost part of Near-The-Black-Sea lowland and the northernmost part of the Crimean peninsula, where the altitudes “subside” below 50 m. above the sea level. A transition between the Chernozemic and the Arid Steppe zones is, according to N.B. Vernander, 20-25 km wide. Within this band the sodicity-affected southern chernozems on the elevated watershed plateaus are gradually substituted by dark chestnut slightly affected soils, while on the slopes the southern chernozems “still persist in presence”. Gradually, the dark chestnut soils “invade the entire space”.
The climate of the arid steppe zone is arid, as the name implies. It is droughty for agricultural crops. The sum of active temperatures reaches 3200-3500°C with a moderate degree of continentality. The winter is mild. Snow cover is shallow and occasionally. There is no snow cover at all.
Annual average amount of precipitation is 307 mm, near the town of Skadowsk snd 350 mm in the northern part of the zone. Humidity coefficient is within 0.4-0.55. In some droughty years the annual amount of precipitation does not exceed 250 mm. By topography the zone is a flat plainland. Only within the interbasin territory between the river basins of the Dnister and Dnipro there are encountered some long ravines with gentle slopes. The amount of flat-bottom (saucer-like) depressims called podas (the result of parent material and soil shrinkage and subsidence) increases to the south. The watershed between the rivers Dnipro and Molochna is particularly rich in them. The areas of podas fluctuate within a wide range between square meters and square kilometers. The podas are the the accumulators of moisture and they alleviate the severity of droughts. Ground water is saline to varying extent. Worm wood, feathergrass, needlegrass, and various halophytes (salsola and suede grass) are the typical species of the natural arid steppe vegetation which is preserved in the Askania-Nova reserve but hardly anywhere else. Parent materials are represented by the loess and loess-like heavy loams and clays, mainly salt-affected to varying extent, though nonsaline parent materials also occur.