- •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.
- •4. Soil texture.
- •2. Plant roots and soil relations.
- •3. Soil fertility and soil productivity.
- •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. Agronomical and ecological roles of som.
Humus is a reflection of soil formation. Type of humus determined in this country by the Ch.a.: Cf.a. ratio has a correspondence to major soil types. Organic matter contributes to plant growth through its effects on the chemical, biological and physical properties of soil. The SOM supplies N, P, and S for plant growth, serves as an energy source for soil organisms and promotes good soil structure. Humus also indirectly effects the plant uptake of micronutrients and heavy metal cations and the performance of herbicides and other agricultural chemicals. The SOM supplies nearly all the N, up to 60% of the phosphate, perhaps as much, as 80% of the sulfur and a large part of the B and Mo. Indirectly, SOM affects the supply of mineral nutrients from other sources.
The amount of N2 fixation by the free-living bacterium Azotobacter is related to the amount of readily available energy sources in the soil, such as carbohydrates and SOM.
The availability of many micronutrient cations is also strongly affected by SOM. Various low molecular weight components of OM (e.g., fulvic acid) form stable complexes (chelates) with Fe3+, Cu2+, Zn2+, and other cations. These shield the cations from hydrolysis and precipitation reactions. Organic amendments (manure, sewage, sludge, etc.) can improve micronutrients availability in alkaline soils and correct Fe and Zn deficiencies in particular.
The amendments apparently release micronutrients already in chelated or release (mineralize) fulvic acid compounds that chelate the inorganic Fe and Zn originally present in the soil.
The SOM may also combine with toxic ions such as Cd2+ and Hg2+, as well as with micronutrient cations at high concentrations and reduce their availability.
Humus affects soil structure and thus soil tilth and moisture retention. The deterioration of structure that accompanies intensive tillage is usually les severe in soils adequately supplied with humus. When humus is lost, soils tend to become hard, compact and cloddy.
Aeration, water-holding capacity and permeability are all favorably affected by humus. The water-insoluble salts of humic acid (with polyvalent cations) are called humates. They tend to be amorphous and glue-like. Heavy (clayey) soils in particular benefit from OM additions through the promotion of aggregation and a granular soil structure. Aggregation yields a loose, open granular structure for good water and air permeability. Humus also absorbs large quantities of water. The fully synthesited humus of a mineral soil absorbs roughly 80 to 90% water by weight from a saturated atmosphere. Micropores within large soil aggregates hold additional water for plants. This may be a major benefit of OM addition to extremely sandy soils.
OM content is most directly related to the sorption of most herbicides and many organic compounds. Recommended herbicide application rates are often higher for soils high in OM content. The soil behavior of organic chemicals, their interaction with SOM is an active area of current soil chemistry research.