UC Master Gardener Program Healthy Soils and Soil Basics be understood but by itself will not The conventional view of soil looks at achieve a healthy fertile soil. three “independent” factors which make up soil and they are structural, chemical The biological component of soil is and biological. The understanding of soil probably the least discussed and perhaps and soil health through the soil food web the most influential factor in achieving soil is looking at the same three factors; but health. The biological component is made rather than looking at each component of bacteria, fungi, protozoa and independently, soil health is achieved nematodes in addition to a variety of when all three are working together, not other soil life. Without good soil biology, autonomously. Let’s consider the three pH alone will determine nutrient factors independently and then how they availability to your plants and manual should work together. inputs will be required to maintain the nutrient levels needed for your plants. Soil texture tells us the size and portion of the particles within a sample, in other Here are some of the microbes found in words the percentage of sand, silt, and healthy soils. Bacteria are mostly clay found in the soil sample. The soil decomposers which feed on plant structure is the way these three elements exudates and fresh organic matter. They are ‘glued’ together to form aggregates of immobilize and retain nutrients in their solids and pore spaces (think granola!) bodies and are very nitrogen dense. Think of them as little bags of fertilizer! The chemical make-up of soils is the Fungi are also decomposers, feeding on conventional way soil fertility is more complex organic matter. The measured. A soil test will tell you the thread-like growth habit of fungi improves soluble values of macro (Nitrogen (N), soil texture, transports water, and phosphorus (P), potassium (K)) and nutrients, and protects against micronutrients found in the sample. It will pathogens. Protozoa, nematodes and also measure the pH of the soil which is a other insects are the predators to critical factor in determining nutrient bacteria and fungi. availability. The test should also measure the soils cation exchange capacity or These three components of structural, CEC (the capacity of the soil to hold chemical and biological support each nutrients) and organic matter percentage. other to form healthy and fertile soil. The The chemical component to soils is biology supports the structural aggregates certainly a key factor and one that should and resulting pores, which allow water and It is the policy of the University of California (UC) and the UC Division of Agriculture & Natural Resources not to engage in discrimination against or harassment of any person in any of its programs or activities (Complete nondiscrimination policy statement can Be found at http://ucanr.edu/sites/anrstaff/files/215244.pdf) Inquiries regarding ANR’s nondiscrimination policies may be directed to UCANR, Affirmative Action Compliance & Title IX Officer, University of California, Agriculture and Natural UC Master Gardener Program gases to freely exchange through those killing off the microorganisms in the soil. pores. The biology also helps transform Once the organisms are gone, you become the chemical nutrients in the soil into a dependent on the synthetic fertilizer. plant available form. To speed up the nutrient cycling process, The way that plants uptake these nutrients many organic farmers create and use is a very complex and fascinating thing but custom blended compost teas. By let’s try and simplify it to understand the suspending the micronutrients of quality importance of the biological component of compost in a liquid form, the plants and soil soil. organisms can access the benefits of the compost/nutrients far more quickly and, if Plants have a symbiotic relationship with the soil is lacking in biodiversity, we can their soils. Plants give up nearly 60 percent inoculate the soils with the necessary of their energy to their roots, which release biology to ensure all necessary components exudates. Exudates are a food source for are available for a healthy, sustainable soil. bacteria and the start of the nutrient cycling process within the soil food web. Soil Diversity is important because every soil is organisms digest organic matter. different. Having a wide variety of bacteria and fungi handles a wide variety of If you are applying fertilizer to your garden, deficiencies. In order for the bi-products of and you have insufficient biological activity the microbiology to be of any value, in the soil, there is no way for your plants to however, the soil food web needs to take up those necessary nutrients and very continue its cycle with the help of little defense against pests and diseases. In arthropods, nematodes and protozoa (the an organic environment, soil organisms shredders, predators and grazers found in need to digest the organic material the third trophic level of the soil food web). (nutrients) and smaller organisms (soil food web) before any plant can benefit from the So, if you are considering taking a healthier, micronutrients. This is why synthetic more sustainable approach to maintaining fertilizers are so harmful and why we have your soil, consider not only the nutrients the become so dependent on them. Once the plants need, but also the biology and the synthetic nutrient is absorbed into the plant, whole ecology necessary to sustain the soil the runoff leaches into the ground, thus food web. 2 .