Healthy Soil Structure = Healthy Soil
by CNF Board Member Judith Podolske:
Healthy soil, the top few inches of earth, is actually a “living environment” with a physical structure. In addition to growing plant roots with their millions of tiny to microscopic root hairs, the soil is teeming with billions of microscopic organisms such as bacteria, protozoa, and fungi that help to break down and dissolve inorganic minerals and decaying organic matter in the water that passes through the soil. Soil structure is composed of aggregations of various sizes and mixes of mineral particles (sand, silt, and clay), varying amounts of decomposing organic matter called humus, and different sizes of pore spaces. These pore spaces are critical for the transport of water, dissolved plant nutrients, and oxygen through the soil, as well as allowing for the passage of the microorganisms and larger organisms such as earthworms, ants, and various insects. But perhaps most importantly for gardeners, the root hairs of plants grow into these pore spaces in search of water, nutrients, and oxygen.
Working the soil when it is too wet or too dry can easily damage and even destroy this vital structure. Breaking up dry soil either by hand or mechanically with a tiller does exactly that-it physically “breaks” the structure and collapses or crushes the pore space. Dry soils should first be given a good watering a day or so before it is time to start digging to “soften” them. Soils that are too wet—especially heavy clay soil (much of the soil found in Chico gardens)—compact and often turn into rock-hard clods of eliminating the pore spaces entirely when worked. An easy test for whether or not the soil is too wet to work is to simply take a small handful and gently squeeze it. If it remains in a clump when you open your hand, it’s too wet to work. If it crumbles and falls apart when you release the pressure, it’s ready to work. Treating your soil as a living environment and protecting its critical physical structure will help to ensure that you will be able to grow healthy plants for many years in the same garden.
electron microscope image of soil microorganisms
