Red soil is a type of soil that typically develops in warm, temperate, and humid climates and comprises approximately 13% of Earth's soil and it contains thin organic and organic-mineral layers of highly leached soil resting on a red layer of alluvium. Red soils contain large amounts of clay and are generally derived from the weathering of ancient crystalline and metamorphic rock. They are named after their rich red color, varying from reddish brown to reddish yellow due to their high iron content. Red soil can be good or poor growing soil depending on how it is managed. It is usually low in nutrients and humus and can be difficult to cultivate due to its low water holding capacity; however, the fertility of these soils can be optimized with liming and other farming techniques.

Red soils are an important resource because they make up such a large portion of farmland on the earth. In countries such as China, India, and Greece, where there are large amounts of red soil, understanding the soil's properties is crucial to successful agriculture. Red soil properties vary across regions and may require different management practices to achieve the best results.

Red soils include multiple soil types (e.g. ultisols, alfisols, oxisols) that are classified as red soil when they develop a distinct reddish color, which can vary from reddish brown to reddish yellow due to their high iron content. In general, red soils possess some characteristics of a good growing soil. They are generally acidic soils, which can be positive for agriculture but, in this case, often cause a lack of sufficient nutrients. These soils are also prone to frequent drought in drier regions.

Red soils are generally derived from the weathering of crystalline and metamorphic rock in areas of high rainfall. Red soil contains large amounts of clay and thin organic and organic-mineral layers of highly leached soil resting on an alluvium red layer. The composition and agricultural properties of red soil vary across regions. One type of red soil may be considered infertile in one region but nutrient-rich in another. There is not a singular composition that classifies all red soils.

Red soils are typically difficult for crop cultivation because high leaching leads to low water holding capacity, low nutrients, low organic matter (humus), and acidification. Fluctuations in the concentration of iron within red soil are found to have significant implications on its fertility and growth properties. The fertility of red soils can be improved with various farming techniques.

The soil liming process helps raise the pH of acidic soils. Because red soils are generally acidic, liming is a valuable farming technique that allows crops intolerant of acidic environments to thrive in red soil. However, modern research suggests that liming may have long-term environmental consequences on the soil. The systematic overflow of water through the soil gets into the organic matter of relevant sophgate of the soil.

Red soils are often deficient in nitrogen, which limits the growth properties of most red soil. Phosphorus and potassium can also become limited after the land has been harvested repeatedly. Nutrient application techniques introduce more of these lacking nutrients to the soil and allow them to restore chemicals that have diminished over time.

Another management practice that can be used to improve the fertility of red soil is incorporating organic matter into the soil. Some strategies employed to practice this include the use of organic manure and establishing proper tillage systems for the land.