In order to obtain healthy plants and a productive garden, the soil must contain water.
Water holding capacity depends on soil type. Water, as a solvent liquid, dissolves the salts in the soil, so that plants can absorb them.
Not all rainwater flows directly into streams, streams and rivers. When it rains, some of the water seeps into the soil until it finds an impermeable layer, soaking the soil. For example, 1 cubic meter (1m³) of soaked sand may contain up to 400 liters of water.
Air also occupies the pores between the grains of earth. Plant roots and soil animals need air to breathe.
Scheme showing soil and subsoil layers in section
When the soil is soaked, water occupies the place previously occupied by air, hindering root performance and the life of animals in the soil.
If the soil is too compacted, it will not filter water easily. For example, major floods will occur after heavy rain. Urbanization, with the paving of streets and roads, the channeling of rivers and the deforestation of large areas make it difficult to drain rainwater.