Whether in a greenhouse or a house plant flower pot, indoor soils recieve no rain, so they behave much as irrigated desert soils.

Because they recieve no or very limited rainfall, soils in greenhouses, hoop houses or other indoor settings experience some of the conditions and processes typical of deserts. Growing plants in them requires the application of irrigation water. The water used for irrigation (unless it is distilled water or pure rainwater) is not pure but contains some dissolved salts, whether it's source is municipal tap water, ground water or river water. The water applied to the soil continuously evaporates from the soil or through the plant, leaving behind the salt. As water is repeatedly added to meet the needs of the plants, the salts accumulate more and more. Capillary flow brings the salty water to the soil surface, especially to the highest points such as the tops of raised beds or even small clumps of soil on the surface. The white substance seen in this hoop house soil in South Korea is salt that accumulated under the black plastic mulch used to prevent weed growth between the chicory plants. Over time (usually just a few years or less), enough salt may accumulate to cause damage to sensitive plants. The best practice is to monitor the salt levels in the soil using a simple electrical conductivity meter. If the hoop house is located in a humid temperate region, the easiest remedy for high salts is to simply remove the roof (transparent plastic ) of the house during the wet winter season to allow the excess rainwater to leach the salts out of the rootzone. For a more arid regions or in the case of a house plant, excess irrigation water can be applied to wash the salts down below the root zone (and into a sink in the case of a house plant with a drain hole in the pot).