The best type of soil for farming is loam. The good balance between sand and clay particles means that it has both large and small pore spaces. This gives supply of air and water. Therefore, the loamy soil retains some moisture for plants to use, but also allow water to drain through it during times of high rainfall. Loamy soils have enough clay for holding nutrients and are reasonably easy to work. Their acidity level is likely to fall within 5.5 to 8.0 on the pH scale.

 Sandy soils are described as “hungry” because they need large and frequent feeding with fertilizers.

The water cycle and water availability on Earth

Water cycle

 Evaporation takes place due to heat. Water from oceans and seas changes from water droplets to water vapour in the atmosphere. Water is also lost from trees and plants, mainly from their leaves. This is transpiration. Evapo-transpiration covers all water losses from land surfaces.

 Condensation is the process by which the water vapour is turned back into a liquid or a solid. Further cooling leads to precipitation, which is all the moisture that reaches the surface irrespective of type.

 Some water particles are prevented from falling directly on the ground by trees and plants, called interception. Some flows over the ground surface, eventually finding its way into streams and rivers. This is run-off. The remainder steeps underground, downwards by infiltration and sideways by groundwater flow.

The role of water within ecosystems

 An ecosystem comprises all living communities in an area together with its non-living natural environment. It is a system because all elements are interlinked.

 Water stress is when a country worries over present and future water supplies.

How do water-poor countries obtain their water supplies?

 One way is to use desalinization. This changes sea water to fresh water, using large amounts of electricity.

 Another way, water-poor countries pump up water to the surface from natural underground stores called aquifers. Rain water that has accumulated during hundreds of years is used to satisfy people’s present water needs.