Basics of Environmental Science

104 / Basics of Environmental Science cent of all farmland is irrigated, ranging from 6 per cent in Africa and South America to ...

Physical Resources / 105 If more water is abstracted from an aquifer than flows in to replenish it, the amount of water availabl ...

106 / Basics of Environmental Science Some of the rain falling on the ground sinks vertically through the soil, as ‘gravitationa ...

Physical Resources / 107 is simpler. Adequate drainage must be installed and irrigation suspended until the water table has been ...

108 / Basics of Environmental Science it proceeds more slowly than in moist ones, for example. Yet the process is remorseless. A ...

Physical Resources / 109 Figure 3.9. Where drainage is excessive, the soil will be generally dry, favouring trees that can root ...

110 / Basics of Environmental Science importance to us and if we are to use it the more we know about it the better. It is so va ...

Physical Resources / 111 The classification may be powerful, but there are attractions in calling Mollisols ‘prairie soils’ (or ...

112 / Basics of Environmental Science meltwater that flowed as rivers and flooded low-lying areas. The waters carried suspended ...

Physical Resources / 113 stones released by frost-shattering from adjacent rock. These stones, most of very irregular shape, wil ...

114 / Basics of Environmental Science underlying deposit, in this case suggesting that a much larger river once flowed, probably ...

Physical Resources / 115 accustomed. Following a series of dry years, in 1934 and 1935 the crops failed and soil reduced to litt ...

116 / Basics of Environmental Science Although soils are now classified according to their composition, their surface horizons a ...

Physical Resources / 117 mediate layer, called ‘gley’, is wet, sticky, and blue because of the reduced iron compounds it contain ...

118 / Basics of Environmental Science Figure 3.14 World distribution of soil orders ...

Physical Resources / 119 of the hydrogen ion concentration) and when it is nearly saturated with hydrogen the colloid breaks dow ...

120 / Basics of Environmental Science In fact, soil erosion is an entirely natural process. Unconsolidated surface material is t ...

Physical Resources / 121 Water flowing across the surface carries particles in suspension, which never touch the ground, particl ...

122 / Basics of Environmental Science gullies, but much more productively. During dry weather the gully is widened, soil added, ...

Physical Resources / 123 Erosion by water may remove more than just the soil. If the land has been tilled, sown, and fertilized, ...