- •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.
2.2. Plant requirements to soil aeration.
Thus we may look upon a well-aerated soil as one in which oxygen is available to growing aerobic organisms (particularly higher plants) in sufficient quantities and in the proper proportions to encourage optimum rates of the essential metabolic processes of these organisms. Under actual field conditions, there are two situations in which aeration is poor: (1) when the moisture content is excessively high, leaving little or no room for gases, and (2) when the exchange of gases is not sufficiently rapid.
All aerobic organisms are unable to function properly in the absence of free oxygen. This is also true for the symbiotic N-fixers and some of the nonsymbiotic ( Azotobacter ) groups. Poor aeration impedes the growth of the plants, particularly the roots, lessens the absorption of nutrients and water and forms certain inorganic and organic substances toxic to plant growth. Tomatoes require high air porosities (up to 20-30%) for best growth. Timothy, if well supplied with N, can grow with a very low air porosity and rice grows normally submerged in water. Sugar beet are very sensitive to aeration otress as well as alfalfa and legumes in general. In peat soils, the aeration porosity should not be less that 40% by volume.
3. Management of soil redox and aeration regimes.
All practices improving soil structure are good for the aeration. They include reduced tillage and the use of mulches (residue cover ), proper organic matter balance by the system of fertilizing and the growth of perennial grasses, wind and water erosion control and prevention of soil compaction under heavy machinery. In overweat soils drainage may be a must. For all practical purposes, soil more than 2 meters above the water table is scarcely affected by it. Soil dewatering or drainage is used to lower the water table when it occurs at or near the soil surface, or to remove excess water that has accumulated on the soil surface. The regular applications of chemical amendments (lime or gypsum) in soils requiring them tend to improve or at least to preserve soil structure and thereby make soil aeration better. Eh and rH2 should be employed in the evaluation of soil aeration for the concrete field crops.
LECTURE NINE.
Soil temperature & soil thermal regime control.
Study outline:
Soil temperature & modes of energy transfer.
Conduction of heat in soil. Heat-related soil properties.
Thermal conductivity of soil.
Thermal regime of soil profiles &its control.
Soil temperature, its value at any moment, & the manner in which it varies in time & space is a factor determining (1) the rates & directions of soil physical processes & the energy & mass exchange with the atmosphere, including evaporation & aeration, (2) the types & rates of chemical reactions in the soil, & (3) biological processes such as seed germination, seedling emergence & growth, root development & microbial activity.
Thermal properties of soils include the specific heat capacity, thermal conductivity, & thermal diffusivity. All these properties are strongly affected by the bulk density & wetness of a soil.