- •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.
4. Maintenance and balance of som.
Soil OM losses are a real problem. Comparison of cultivated soils with their virgin variants indicate an average reduction of about 35% in respect to their N. This means a more or less proportional lowering of total OH. It is impossible in most cases to maintain the OM and N of cultivated soils on the level of virgin ones. Nor is it necessary or even desirable. Yet a decline in OM content of 30 to 40% is serious and should go no further. It is important to maintain SOM above certain level. For Ukraine it is very important to reduce soil erosion to tolerable levels. Up to 18 mt/ha of topsoil from Ukrainian plow land is lost to water erosion every year, which means the loss of over 0.5 mt/ha of soil humus. In the forest-steppe zone the annual OM losses exceed 1 mt/ha. It means the necessity to apply the additional 15 mt of farm manure per hectare of a crop rotation. A metric ton of humus is estimated in Ukraine to cost 200 dollars. Farm manures and composts should be applied at sufficient rates. Perennial grasses and green manure crops should be practiced in field crop rotations. In many countries the most important source of OM are the current crops themselves. Restricted tillage and the proper residue management are important for soil conservation and OM losses prevention. Intertilled crops are associated with humus reduction. Sod crops promote the highest possible yields of humus. Everyone knows that SOD BEGETS HUMUS. Good soil management seeks to adjust the addition of organic residues, the physical and chemical conditions of the soil, the sequence of crops and the losses through biological activity in such a way that paying crops may be harvested without reducing the humus supply of the soil below a definite level. Any system of agriculture that does not do this is impractical and unscientific.
LECTURE FOUR.
Colloids and absorbing capacity of soils.
Study outline:
1. Origin and composition of soil colloids.
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.
1. Origin and compositing of soil colloids.
Soil colloids are composed of particles within 200 to 1 nm in size. There are two distinct types of colloidal matter: inorganic and organic. They may exist in such intimate intermixture that some researches propose to differentiate the third type: organic – mineral colloids, and such is the tradition in our country. The inorganic type is present almost exclusively by as clay; the organic is represented by humus. Organic – mineral colloids are mostly adhesion complexes between the clay and soil humus. By clay we mean here silicate and non-silicate types of it.
The origin of soil colloids is connected with the origin of soils, i.e. with the processes of weathering and soil formation. Colloidal micelles may be formed as a result of the aggregation of molecules and that of the disintegration of larger than colloidal particles. A great specific surface and absorbing capacity of soils are due mainly to the presence of colloidal matter. Thus 4 % of colloidal fraction in the soil is responsible for 80 % or more of its specific surface. Some clay particles (kaolinite) may expose only a certain amount of external surface. But this is by no means all. In some clays there are internal surfaces as well. But even the external surface area of one gram of colloidal clay is at least 1,000 times greater than that of 1 gram of course sand. Soil humus has specific surface within 500 – 1000 m2g-1 and adsorbing capacity (CEC) within 300 – 800 m.-eq. per 100 g of soil. Smectite particles have specific surface up to 600 – 800 m2g-1 and CEC within 80 – 120 m.-eq. per 100 g of soil.