Chapter 2: Soil Composition

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1)Give the ideal composition of soil.

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2)Where is mineral matter derived from?

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3)Why is the % air and water said to be dynamic?

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4)Explain why soil pore space is so important?

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5)Explain how soil pore space can be affected?

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6)Give the composition of mineral matter.

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7)List the in order of increasing size the mineral matter particles.

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8)Explain the properties of gravel and sand.

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9)Explain the properties of silt and clay.

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10)What is meant by ion exchange?

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11)Why is colloidal clay so important?

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12)Describe the relationship between surface area, ion exchanging power and particle size?

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13)What is meant by the term cations?

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14)What is an anion?

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15)Describe the properties of organic matter.

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16)What is humus?

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17)Describe the relationship between particle size and physical and chemical properties.

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18)What is colloidal humus?

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19)Compare soil air and atmospheric air.

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20)Why is air needed in soil?

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21)How can air be removed from soil?

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22)What is diffusion?

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23)What do capillary forces mean?

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24)Why is soil water often referred to as the soil solution?

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25)What is soil texture?

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26)Explain what is meant by the physical properties of soil.

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27)How can soil texture be determined?

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28)What is the soil texture triangle used for?

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29)Give one desirable property and one undesirable property of a sand, silt, and loam and clay soil.

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30)How can soil structure be defined?

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31)Compare (giving at least 3 points) the following soils: a clay soil, a sandy soil and a loam soil.

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32)How can soil structure be defined?

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33)Compare a structured and structureless soil.

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34)What is meant by flocculation?

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35)What is aggregation?

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36)What is a ped?

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37)How can flocculation be promoted?

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38)How is structure development accomplished in a field?

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39)Compare cementation and separation.

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40)Explain what factors affect cementation and separation.

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41)What is meant by a “permanent grassland”?

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42)What is the optimum level of air in soil?

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43)Why might a sub soiler or ripper be used for?

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44)What is a polarised water molecule?

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45)What is hygroscopic water?

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46)Compare hygroscopic water, capillary water and gravitational water.

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47)What is meant by available water capacity?

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48)Compare soil that is at (a) Saturation, (b) Field Capacity (c) Permanent Wilting Point.

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49)Compare permanent and temporary wilting point.

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50)How can a crop be put under “moisture stress”?

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51)What is meant by “unsaturated flow” and “saturated flow” when talking about water movement.

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52)What is meant by a perched water table?

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53)Explain what effect does soil temperature have?

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54)What is Van Hoff’s Law?

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55)Describe an experiment to estimate the soil texture by feel and feel.

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56)Describe an experiment to determine the soil textural class.

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57)Describe an experiment to estimate the soil texture by sedimentation.

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58)Describe an experiment to demonstrate flocculation of clay.

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59)Describe an experiment to demonstrate the effect of structure formation on total pore space.

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60)Describe an experiment to determine the infiltration rate and permeability of a clay and sandy soil.

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61)Describe an experiment to determine the threshold soil temperature for grass growth.

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