- Title: [[How To Build Great Soil - A Soil Science Masterclass with Dr Elaine Ingham]] - Type: #source/lecture - Author: - Reference: https://www.youtube.com/watch?v=ErMHR6Mc4Bk - Published at: - Reviewed at: [[2022-04-27]] - Links: [[Organic Chemistry]] --- ## The soil food web The fundamental problem is that we need to store energy somehow. The primary source or energy available for the last several billion years is sunlight. [[Photosynthesis|Photosynthetic] bacteria were the first organisms to store sunlight energy chemically into carbon chains (carbon-carbon bonds). ^[Plants have only been around for the last ~1B years. Bacterial predate plants by ~3 B years] ^[Organic refers specifically to carbon chains, e.g. activated carbon isn't considered organic. In the natural world, it takes life to build up carbon chains] **Trophic (nutrition) levels** 1. Photosynthesizers 2. Decomposers, mutualists, pathogens, parasites, root feeders 3. Shredders, predators, grazers 4. High-level predators 5. Fifth and higher trophic levels are higher and higher levels of predators. ![[_Media/soilfoodweb.jpg]] ## Root depth, compaction layers, water dispersion, and oxygenation "As plants evolved in complexity, most have a tendency to have deeper root systems. Weeds have the most shallow root, putting only about 20% of their energy into their root systems. Grasses, brassicas, shrubs and trees put progressively more energy into their root systems (coinciding with reduction and fungi-fication of the soil ecology). If roots aren't going deep, it's because we've somehow damaged the soil." [[Water]] will tend to not diffuse across boundaries of different densities ^[[[Impedance Mismatch]]]. It takes less energy for water to spread out sideways through less compact material when it hits a hard pan due to a [[compaction layer]]. As [[water]] pools, it gets harder and harder to pass [[oxygen]] through the soil and that area will go [[anaerobic]]. The aerobic bacteria will quickly die off and anaerobic bacteria will take over creating a hostile environment for the root system. ### Root System Energy content Plants transfer energy they capture from the sun into their root systems **Energy fixed into roots** - Weeds: 20% - Grasses: 60% - Veg: up to 75% - Shrubs and Trees: 80% The energy is transferred into the root system in various forms for different functions - Build structural roots. Prevents the plant from falling over and firmly anchors it in the soil - Take up nutrients (lateral roots). Note this is only through diffusion of bio-available nutrient molecules. The plant root system can't produce enzymes to break down organic matter on its own - Make exudates to feed the symbiotic soil ecology. 50% of energy put into the roots by plants are released as mostly simple sugars and a little bit of protein and carbohydrates. The specific type and combination of exudate will depend on the type of bacteria or fungus the plant wants to promote to solubilize the nutrients it *currently* needs. **None of the soils lack the nutrients, what they lack is the organisms to solubilize the nutrients so the plants can take up the nutrients** ## Structured Soil Structured [[soil]] will, among other things, absorb and disperse water much more easily and be better oxygenated. Healthy soil structure can NOT be accomplished through a merely chemical process. Living organisms in the soil build healthy soil structure. ### Building soil structure 1. Build your aerobic bacterial community. Bacteria will exude compounds that act like glues to allow sand, silt, clay and organic matter to start clumping together into [[soil micro-aggregates]]. Aerobic bacteria naturally produce sticky exudates so they can stay close to their food source when disturbed (e.g. when water comes rushing through). The [[ph]] of aerobic bacteria exudate glues is alkaline. Anaerobic bacteria and environments have a lower, acidic ph and will be detrimental to all of the organisms required for healthy soil ecology. The ph of the soil is primarily a function of the life in the soil, NOT the content of the substrate. 2. Mycorrhizal fungi mechanically bind micro-aggregates into larger soil aggregates. Fungi don't produce very much glue (small amounts of glomulin but not nearly as much as bacteria). The physical mycorrhizal structure weaves and binds together macro-aggregates and creates larger airways and passageways in the soil. Fungi regulate the ph of soil around them by releasing organic acids. Aerobic fungi keep ph around 5.5-7 (slightly acidic). 3. Protozoa break up bacteria-bound, solubilized nutrients to make them available to the plants. Without protozoa, all the energy the plant has put into the root system as exudates stays locked up in the fungi and bacteria in and around the root zone. ^[A good way to tell if you're aerobic or if you've gone anaerobic is the present of flagellates (aerobic) vs ciliates (anaerobic).]