Soil Around the World Answers

Soil fertility comes from a balance of the organic matter and mineral nutrients in a soil. The histosols of peat pogs are soils rich in organic material but poor in mineral nutrients, and are not fertile. Conversely, aridosols (desert soils) have an abundance of mineral nutrients but a dearth of organic matter and are also not fertile.

Fertile soils are generally those with well-developed horizons of both mineral and organic matter. In the case of the soils of flood plains, the soils lack such clearly defined, well-developed horizons and so they would not be expected to be fertile.

The over-irrigation of soil leads to water penetrating into deep soil layers and dissolving the salt present there. As the water evaporates out of the soil, the salt is drawn towards the surface with the water. This results in salt accumulating near the surface and reducing soil fertility.

Soil compaction results from human activities that press down on soil and eliminate much of the pore space between soil particles. This compaction and the loss of pore space reduces the soil’s ability to store water meaning that less water is absorbed by the soil when it rains. Instead the water flows as runoff, increasing the severity of flooding and erosion in the area.

Volcanic soil is rich in minerals from the volcanic deposits laid during eruptions and the lush plant life that adds necessary organic matter. The soil has not been leached of the minerals so it retains high fertility.