Gericke originally defined hydroponics as crop growth in mineral nutrient solutions, with no solid medium for the roots. He objected in print to people who applied the term hydroponics to other types of soilless culture such as sand culture and gravel culture. The distinction between hydroponics and soilless culture of plants has often been blurred. Soilless culture is a broader term than hydroponics; it only requires that no soils with clay or silt are used. Note that sand is a type of soil yet sand culture is considered a type of soilless culture. Hydroponics is always soilless culture, but not all soilless culture is hydroponics. Many types of soilless culture do not use the mineral nutrient solutions required for hydroponics.

Billions of container plants are produced annually, including fruit, shade and ornamental trees, shrubs, forest seedlings, vegetable seedlings, bedding plants, herbaceous perennials and vines. Most container plants are produced in soilless media so represent soilless culture. However, most are not hydroponics because the soilless medium often provides some of the mineral nutrients via slow release fertilizers, cation exchange and decomposition of the organic medium itself. Most soilless media for container plants also contain organic materials such as peat or composted bark, which provide some nitrogen to the plant. Greenhouse growth of plants in peat bags is often termed hydroponics, but technically it is not because the medium provides some of the mineral nutrients. Peat has a high cation exchange capacity and must be amended with limestone to raise the pH.

Advantages

While removing soil-grown crops from the ground effectively kills them, hydroponically grown crops such as lettuce can be packaged and sold while still alive, greatly increasing the length of freshness once purchased.

• No soil is required.
• Soil borne diseases are virtually eliminated.
• Weeds are virtually eliminated.
• Fewer pesticides may be required because of the above two reasons.
• Edible crops are not contaminated with soil.
• Water use can be substantially less than with outdoor irrigation of soil-grown crops.
• Solution culture hydroponics does not require disposal of a solid medium or sterilization and reuse of a solid medium.
• Solution culture hydroponics allows greater control over the rootzone environment than soil culture.
• Hydroponics is often the best crop production method in remote areas that lack suitable soil, such as Antarctica, space stations, space colonies or atolls, such as Wake Island.
• In solution culture hydroponics, plant roots can be seen.
• Hydroponics is considered high-tech and futuristic and so appeals to many people.
• Hydroponics is excellent for plant teaching and research.

All text is available under the terms of the GNU Free Documentation License.