The Differences Between Soils

Soil pH

• Soils are commonly divided into three types, based on their pH levels. Soils with a pH below 7 are classified as acidic, and those with levels above 7 are referred to as alkaline. Soils with a pH of 7 are classified as neutral. Soil pH determines the availability of nutrients to plant roots. Some nutrients are more soluble at certain pH levels, which makes them more readily available to plants. For example, plants in soil with pH below 5.5 may have calcium, magnesium and phosphorus deficiencies.

Soil Texture

• Soil texture refers to the size of and space between soil particles. The texture of soil influences a variety of its other characteristics, including drainage, aeration and soil erosion, as noted by the Cornell University Cooperative Extension. Soil texture is typically divided into three primary categories: sand, silt and clay. Sandy soils have large particles and pores, while clay soils have very fine particles with little space between them. Silt lies between these extremes.

  You might have also heard of loam soils. The term loam does not refer to a specific type of soil texture but, rather, describes soils with an ideal ratio of sand, silt and clay particles.

Soil Structure

• Soil structure is closely related to soil texture but differs slightly. Soil structure refers to the shape of its aggregates, or soil tilth, which are groups of soil particles that are bound together. When soil particles come together, they usually form in certain ways. Some soil particles form granular structures that resemble cookie crumbs, whereas others might resemble long plates placed on top of each other. The four common soil structures are granular, platy, blocky and prismatic. Soils with good tilth tend to have open pores that allow for plenty of aeration but also retain enough water to nourish plants.

Amending Soil

• If your soil has undesirable qualities, you can usually amend, or mix, it with various products. Incorporating organic matter improves water retention and aeration in heavy clay or light sand soils. Types of organic matter include compost, manure and peat moss. Fertilizers are usually used to adjust nutrient levels, although some might also effect soil pH. Generally speaking, lime increases soil pH, and other products, like elemental sulfur, peat and aluminum sulfate, lower pH levels.