4.4 Give English equivalents:

Способность почвы удерживать воду, отдельные частицы, крупные частицы, мелкие частицы, температура почвы, минеральный состав, материнская порода, органические вещества, мелкозернистая почва, крупнозернистая почва.

4.5 Answer the following questions:

1) How will density and porosity affect plant growth and soil structure?

2) How can a farmer change the soil structure for better or worse?

3) Why can a soil with a fine texture store water efficiently than a soil with a coarse texture?

4) Can we measure colour scientifically?

5) How do you know how much water you need to grow a crop?

6) How do soil physical properties affect the soil’s ability to hold water?

4.6 Say if these statements are correct:

1) Soil physics are extremely important for agriculture.

2. Soil is made of particles of the same size.

3. Physical, chemical and biological forces in nature work together.

4. Salinity severely affects structure of the soil.

5. Coarse textured soils have high porosity but the pores are very small.

6. Fine textured soils have high porosity but the pores are very big.

7. The colour of soil depends on the present organic matter.

8. The oxidized iron compounds give light gray colour.

9. Soil water is very significant factor in planting.

Text 5 Soil chemistry

5.1 Read the following international words and translate them: chemical, characteristics, reaction, energy, electrons, atoms, ions, positively, negatively, oxygen, erosion, toxic, elements, percentage, microorganisms, bacteria, result, problem, radius, kilometers, biochemical, concentration, process, membrane, effect, capillary.

5.2 Say it in Russian: chemical characteristics, organic matter, mineral composition, environment, chemical reaction, an attractive force, new compounds, particles, organic matter particles, sands, alkaline, acidic, basic, neutral, deficiency, excess, decomposition, acidification, acidic compounds, salts, soil surface, internal drainage, lack of water, toxic effect, alkalanization, salinity.

5.3 Read the following chemical terms: hydrogen, oxygen, iron, zink, nitrogen, phosphorus, sulphur, carbon dioxide, carbonic acid, calcium, magnesium, sodium.

5.4 Read and translate the text with the help of a dictionary.

Soil chemistry studies the chemical characteristics of soil which depends on their mineral composition, organic matter and environment.

Chemical reactions occur when substances either combine or break apart to form new substances with identifying properties that are different from the original substances.

Cation Exchange An example of chemical properties in soils in which positively and negatively charged particles (ions) within the soil react to one another. This is important for soil fertility as some nutrients remain available in the soil and are not leached readily.

Soil pH pH is a measure of the hydrogen ion activity within the soil. Soils range from acidic (low pH or high free hydrogen ions) to alkaline or basic (high pH). A pH scale ranges from strongly acidic (pH of 0) to strongly basic (pH of 14). Most soils are within a pH range from 4.5 (considered strongly acidic for soils) to 8.5 (medium alkaline). The best growth for the greatest variety plants takes place within a 6.0 to 7.0 range (slightly acidic to neutral). Some plants thrive in an alkaline environment while others prefer more acidic soils.

While the pH of soils may have some direct effects on plants themselves, it is the interaction of soil pH and plant nutrients that is important soils which are higher in acidity or alkalinity levels can result in deficiencies or excesses (that may be toxic) of certain kinds of elements. For instance, higher alkalinity can make elements such as iron, manganese and zink less soluble and therefore less available for plant absorption. Deficiencies of these elements can cause poor growth and poor plant health. Higher acidity can result in a higher percentage of certain substances that are absorbed in solution by plants.

The pH of a soil can affect the activities of microorganisms, which then affects the level of nitrogen, phosphorus and sulphur in the soil. As with plants, most organisms prefer a near-neutral range. Outside this range, the numbers of microorganisms and the rates of their biochemical activities decrease. This affects certain nutrient levels as bacteria and other life forms are involved in decomposition and cycling the matter. Plant producers may use soil pH to help determine soil nutrients that may be lacking and the appropriate way to help the problem.

Acidification Acidification may be the result of the following:

1. In forested and parkland areas, where there is a greater amount of vegetation combined with moist and warm conditions, decomposition releases carbon dioxide. This combines with soil moisture to form carbonic acid.

2. Acid rain is formed by water combining with the emissions of gases (sulphur dioxide) from thermal electric sites and oil refining operations.

3. Some chemical fertilizers entering into solution in the soil will produce acidic compounds. Greater applications of particular kinds of fertilizers are increasing soil acidity in some areas.

S alinity Salts that are naturally found in the ground are brought to the surface as dissolved substances in water. As the water evaporates, the salts are left behind, thereby increasing the salinity of the soil.

Higher salt levels negatively affect plants and soil organisms. Small soil organisms are similarly affected by high salt concentrations in the soil.

Salts also affect the structure of soils by causing salt clumps to break down more quickly. This leads to soil layers becoming more dense, restricting air and water movements and making conditions less favourable for plant roots and microorgansms.

5.5 Give English equivalents: органическое вещество, образование почвы, плодородие, минеральные питательные вещества, способы тестирования почвы, глинистые частицы почвы, щелочная окружающая среда, плохой рост, другие формы жизни, влажные и теплые условия, кислотные дожди, операции по очистке нефти, середина лета, во всех случаях, застой воды, растворенные вещества, отрицательное влияние на растения и почвенные организмы, высокая концентрация соли.

5.6 Choose the proper definition from the right column:

Soil heavy, productive, acid, chemically, wet

Condition acid, acidity, alkaline, neutral, natural

Concentration high, solid, organic, low, absorbing

5.7 Answer the following questions:

1. Why do soils vary greatly in their chemical make-up? What is it due to?

2. What is “acidity” of soil?

3. What is “alkalinity” of soil?

4. What is “salinity” of soil?

5. What is neutral soil?

6. What is pH value?

7. How does salinity affect the soil?

5.8 Explain the meaning of the symbol “pH”.

5.9 Explain the terms “acid soils”, “alkaline soils” and “saline soils” in English.

5.10 Choose the right word from those given in brackets:

Plant Foods in the Soil. All the main plant foods are found in a normal soil. (some, same) of each plant food is there in such a form them the plant can use it. This is known (as, that) available plant food. Some more of it is in a form which the plant (can, cannot) use at the moment. Such plant food is said to be unavailable. To become available it (can, may) need to be changed chemically in some way.

Trace elements, the other plant foods which are needed in very (small, large) quantities, are found (naturally, artificially) in most soils. Sometimes one particular plant food is short and this (excess, deficiency) can cause damage to crops, livestock or both.