Loamy Soil Definition

Sand, Silt and Clay

• Soil texture is the term for the combination of different sizes of mineral particles -- sand, silt and clay -- in the mixture. Soils can be classified into one of four textural classes: sand, silt, loam and clay. Sand has the largest particles and a coarse texture; clay has the smallest particles, making it fine-textured. The proportions of the three types of particles determine the quality of drainage and aeration, and the rate that organic matter breaks down in the soil.

Loam Soil

• Loam is an ideal mixture of sand, silt and clay. It's made up of 40 percent sand, 40 percent silt, and 20 percent clay, a combination that retains moisture while allowing adequate levels of drainage and oxygen. Slightly higher sand content -- 50 to 60 percent sand -- with more than 20 percent silt and not more than 20 percent clay, is called sandy loam. Similarly, clay loam and silt loam are more variations in the loam class.

Field Test

• You can estimate soil texture using the field hand test. Take a handful of damp soil and squeeze it into three shapes: cast, thread and ribbon. Form a lump in your clenched fist for the cast, roll soil between your palms into a thread shape and squeeze the soil between your thumb and index finger for the ribbon. A loamy type soil holds the shapes, but the thread and ribbon break apart to some degree, when you handle them.

Soil Structure

• Only extreme measures change soil texture, but soil structure can be improved. Soil structure refers to the way the particles are assembled. If clay particles are consolidated, the compacted mass of particles becomes impenetrable to plant roots, water can't drain and oxygen isn't available. Soil management strategies, such as increased organic material and reduced tillage, can adjust soil structure to a condition that nurtures plants.