When there is no water available, they die. Excess water, porosity, air and compaction Roots expel carbon dioxide into the soil and absorb oxygen, which means air and porosity are a crucial part of the plant s environment. A few highly specialised plants, such as mangroves, have the ability to feed air through to the roots. Most plants, however, will stop growing and eventually die if air is excluded from the roots by waterlogging or compaction. Soil compaction can arise from excessive application of water, as occurs in flood irrigation, or mechanical action, as from large sprinkler drops.
Plant growth is reduced by the lack of air in the root zone.
Nutrients Nutrients are obtained by adding fertiliser, by the decomposition of organic matter, and by biological action. Many soils, particularly clays, can be rich in nutrients, but these are locked into the soil and are not available to the plant. Micro-biological action can release these nutrients. The plant will be killed by osmotic pressure sucking water out of the plant. Excess water and nutrients Excess water in the soil with insufficient nutrients creates weak solutions and a high osmotic gradient.