Let’s talk about dirt! Everything we do in the garden starts with the soil. Building healthy, happy, living soil is one of the biggest components to successful gardening. So it’s only natural that conversations about the health, maintenance and condition of the soil in our gardens happen often.
Understanding what makes “good” soil is important. What is also important is understanding the terminology used when discussing soil. Terms like texture and structure help us communicate the composition of our soil. Knowing the proper vocabulary for describing the soil used in the proper context is important, so let’s go over a few key terms to get the conversation started:
Soil Vocabulary in Context
When discussing soil we use the word Texture to describe the relative composition (ratios) of sand, silt and clay in a given sample of soil. Soil texture is important in understanding various soil values and potentials such as compaction, drainage, retention, construction and biological activity. Soil texture is also important as it is associated with potential fertility and crop productivity.
Proper soil is composed of a combination of varying particle aggregate units referred to as microaggregates (smaller units) and macroaggregates (larger units). A well structured soil will have a balanced combination of these which give it stability, structure and creates space for air,water and living organisms within the soil. Soils with good structural stability will generally have more macroaggregates and macropores while poorly structured soils (like sand) will have more microaggregates. Poorly structured soils can be silty or have highly compacted clay.
Oxygen is required by microbe and plants for respiration. Aeration is the process by which oxygen is circulated through, mixed in or dissolved in a given medium…in this case, soil. Proper soil aeration requires proper soil texture and structure. A porous soil creates pockets for holding oxygen in the soil, making it available for the microbe populations and for plant roots. Poorly aerated soil will become anaerobic and lead to the buildup of toxic substances and slow nutrient uptake by plants.
Water retention refers to the moisture holding capacity of soil. Clay type, soil structure and presence of organic material play a major role in a soil’s ability to retain water. Soil moisture can help against flooding, promote healthy and active soil biota and plays a significant role in potential plant growth. The maximum amount of water a given soil can hold is referred to as Field Capacity, while soil so dry that plants cannot take remaining water from the soil is called the Wilting Point.
Also referred to as Soil life, soil fauna, or edaphon. Biota is a collective term that encompasses all the organisms that spend a significant portion of their life cycle within a soil profile, or at the soil-litter interface. These organisms include earthworms, nematodes, protozoa, fungi, bacteria and different arthropods. These living organism are instrumental in the bioavailability of nutrients, the decomposition of organic material, the breakdown of toxic materials, creation of good soil structure, the development of healthy root systems and resistance to disease and pests.