Red soil is soil that has a reddish tinge as a result of the presence of iron compounds in it. This soil can form from iron-rich sediments or the compounds may develop in the soil as it weathers. There are a number of different kinds of soil that is red, and simply identifying the color does not provide very much information about it other than a verification that it is probably high in iron. For more information about a specific soil, testing is needed to learn about its composition.
This type of soil tends to form in climates that are warm, temperate, and moist. Sometimes, red soil is left over from older climate conditions, and in regions where iron-rich sedimentary rock is present, the rock provides clues into the prior climate. Deposits often form in bands, explaining the sometimes striped appearance of sedimentary rocks with red, yellow, and orange materials. Not all moist, warm, and temperate climates have soil that is red, but in those that do, it can become a problem for farmers and gardeners.
Red soil can be low in nutrients, and the iron oxides in it can cause problems for plants. Farmers and gardeners may enrich the soil by working in additives and organic materials to create a more even balance of nutrients. Another option is to lay richer soil over it, or to remove the poor soil and replace it with better.
The presence of this soil can provide important information about the environment and the climate. When people identify reddish soil in areas where they want to farm or garden, samples can be sent to a soil lab for analysis to find out whether or not the soil can support plants. If the soil needs to be supplemented, the results of the testing can be used to determine which supplements need to be applied and to find the appropriate concentrations.