Soil Texture

March 10, 2021

Soil Texture -  \ ˈsȯi(-ə) ˈteks-chər / - noun

The relative content of particles of various sizes, such as sand, silt and clay in the soil. Soil texture is a classification of the soil's physical properties (particle size and where it comes from), rather than chemical properties (nutrient contents), though the physical properties can affect the ability of the soil to hold nutrients, as well as water - making the two interconnected. Texture also influences the ease with which soil can be worked, the amount of water and air it holds, and the rate at which water can enter and move through soil.

Soil Texture in the Forest Garden

Most soils are a mix of the three main mineral particles: sand, silt, and clay. The proportion of each in the soil determines the texture: how it feels, how it holds water and nutrients, and how it should be managed. The particle size matters because the amount of space between particles influences how things move through them. Clay particles are the smallest and, as a result, they bind together closely and can be compacted. This leads to heavy soil, unaerated soil, that does not drain well. Water rests on top rather than infiltrating through. Sand particles are the largest, so soils with a high proportion of sand particles have a lot of space between particles. As a result, water flows through this soil very quickly and the soil has trouble retaining water and nutrients. Silt particles are a size in between sand and clay. The best soil, in which we aim to raise our seedlings and vegetables is loamy soil. Loam contains a good balance of the three soil materials mentioned above. It is dark in color and soft and crumbly in your hands. It holds water and nutrients well, but also allows for drainage and movement of air between soil particles and through the root zone. Many of the techniques that are employed through the Forest Garden approach (composting, alley cropping for green manure, nitrogen fixing plants) help move soil from less desirable textures (heavy clay or sand) to more desirable textures through the addition of organic matter, beneficial microorganisms, and aeration. 

Want to learn how to determine what soil texture you are working with? Check out Chapter 5 of the Technical Manual here.

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