(The following is from my monthly newsletter. This series began in March 2022 and has continued for nearly a year, with its final installment in February 2023. Below is the “better” edited version I initially emailed my followers.)
Nutrients can be cycled with the help of the flow of solar energy and water.
What is nutrient cycling, you ask? It’s a movement of nutrients from one organism to another in a complex, biologically diverse loop that involves poop, death and decomposition, and the soil. Both flora and fauna play a crucial role in the nutrient cycle.
Nutrient cycling doesn’t happen as quickly or is as noticeable as the water cycle. However, it is also a perpetual cycle that never ceases and has been around for billions of years. Nutrients include the all-too-famous elemental carbon, hydrogen, oxygen, phosphorus, nitrogen, calcium, potassium, magnesium, and many others; basically, most minerals and elements you can find on the periodic table.
Think of the nutrients that you need for your health. Check out the Nutrition Facts label on a NY steak (found online) or a box of Cheerios, and you’ll see the various nutrients in there. Pay the most attention to the minerals like those mentioned above. Vitamins are much, much more complex to track because they are biochemical compounds synthesized by microorganisms and readily break down or denature after a particular time or under certain conditions.
The Circle of Life
Aside from Disney’s Lion King pun, the nutrient cycle is every bit a part of this “circle of life.” Nutrients are moved in a complex loop that existed before birth and continues after death.
Nutrients are cycled when animals eat other animals, animals eat different plants, and plants “eat” the remnants of animal carcasses, the latter in an indirect manner. Nutrients are also cycled when animals and plants die. However, animals don’t just keep all the nutrients they eat to themselves. They excrete what they don’t need in their urine and feces (or, with birds and reptiles, feces that contain very concentrated amounts of uric acid). These wastes contain many nutrients that get cycled back into the “circle of life” ecology.
Now, that’s the above-ground nutrient cycle. What about below-ground? Soil ecology is equally essential to feed life above ground. Any animal wastes, dead animals and dead plants are broken down by soil micro-organisms, macro-organisms, and other soil-borne organisms into finer and finer components. These organisms are also continually eating others or being eaten. Plant roots are also a part of this “black market” biome, bartering and trading with bacteria, archaea, and fungi for nutrients and water in exchange for liquid carbon. These nutrients plants receive are transported up into the stems and leaves to be used, so the cycle continues.
It’s Not Independent
The nutrient cycle depends on “decomposing sunlight” to function. Decomposing sunlight is the energy that fuels flora and fauna to interact and feed off each other, perpetuating the nutrient cycle. Water from an effective water cycle is also necessary. Most nutritional compounds are water-soluble, making them easily transportable in water (except some fat-soluble vitamins). Without water, nutrients would remain stagnant. A diverse biological community is also crucial, something we’ll discuss next month. Basically, healthy soil begets healthy organisms, maximizing the ability for minerals and nutrients to cycle.
What about rocks? Even so, with the power of water that can carve and smooth out rocks, as you often notice at the bottom of rivers and streams, mineral particles work with water–either as soluble compounds or as minute particles being moved by the power of water–to then “become” another part of the nutrient cycle. Microbes can even work to break down rock material, even if it takes a few million years. It all works together.
Individual nutrients and minerals are also not independent of each other. They will influence the quantity of different nutrients a plant or animal can take up or in, respectively, based on the concentrations already there. Sometimes, imbalances occur, causing toxicities or deficiencies. For example, calcium is influenced by or influences phosphorus, magnesium potassium, and other elements. Hydrogen affects life and other mineral compounds in the form of acidity, neutrality, or alkalinity.
Finally, the speed at which nutrients move from one organism to another or from the soil to plants varies from mineral to mineral. Bioavailability depends on the soil biology types available to convert certain minerals from inorganic to organic, plant-available forms. Phosphorus, for example, is slower to move in the soil than nitrogen. All such information is complex and fascinating and would take up way too much reading time to include here!
Plant Residue (“Litter”) Plays a Role…
Since this series is about regenerative grazing, we cannot leave out the importance of plant residue or, as my university range professor always called it, “litter.”
A couple of months ago, I discussed the importance of litter as a means of covering the soil. In the context of the water cycle, litter is important to slow the impact of rain drops hitting the soil surface at 9.8 meters per second. However, in the context of the nutrient cycle, litter also returns nutrients to the soil. How?
Litter must break down to return nutrients to the soil. This decomposition releases those nutrients to be made useable again by soil microorganisms, other plants, microscopic animals, and others. Without this decomposition, the remaining litter remains, oxidizing by weathering. Not much life can use “inert” plant material that doesn’t have the active biological community to break it down.
That said, there are three main ways litter is broken down.
- Mechanical Forces
- Biological Forces
- Other Forces
Mechanical forces actively shear, crush, pulverize, shred, or chop up the dead plant material. Trampling by the hooves of large (and small) herbivores is a mechanical force, as does hail or heavy rains. Other animals with padded feet (or shoes) don’t necessarily count as a mechanical force because there are not enough of them, compared with grazing/browsing herbivores, to make an impact. However, they still count as a mechanical force much less.
Biological forces are the activity of “all creatures great and small,” pardon the James Herriot pun. Tiny organisms and large organisms work to break down the litter by eating and exuding gastric and salivary juices (among other biochemical compounds non-plant living organisms are capable of producing for the sake of digestion), using some of it for their own body, and excreting the rest as waste. More famously, evidence of such forces is the renowned cow pie, for example. Road apples (horse dung), goat/sheep pebbles (more dung), earthworm castings, and other excrement also count as evidence of the impact of biological forces on plant litter. More specifically, these are your Soil Health Improvement Tools!
Finally, “other forces” include all forces that aren’t biological or mechanical. You could say that they would be more or less “chemical” forces because the exothermic chemical reaction of fire and the deterioration by oxidation certainly count as such.
The fire quickly “breaks down” litter but with the heavy cost of a lot of smoke and carbon dioxide emitted to the atmosphere. Fire also tends almost to destroy all other life that is on that piece of land. While the fire is good in some respects, and using it largely depends on your context, it’s not the ideal force to be used in the cycling of nutrients.
Oxidation of litter is probably just as harmful, if not worse, than fire because the material stays behind and tends to choke out any potential for new plants to emerge. This is because it prevents sunlight from getting to the soil surface and water from getting down. (I’ve also seen it keep too much water in the root zone, causing root rot. Pick your poison.) Oxidation occurs in brittle-tending to very brittle environments, where fire has been suppressed, partial rest is rampant, and not enough large-hooved herbivores are around to turn that material into dung (containing a lot of still-active biological organisms that such arid regions need).
As a result, we should be able to see that biological forces are the most ideal for cycling nutrients. Wouldn’t you agree?
Conclusions
As we end the discussion about nutrient cycling and find this a great segue into next month’s debate around community dynamics, we can see that our management still plays a significant role in capturing sunlight, creating an effective water cycle, and cycling nutrients. You probably noticed I negated to talk about carbon cycling, and that’s due to one reason: carbon cycling is not much different than discussing how other nutrients cycle, like nitrogen. Capturing nitrogen from an atmosphere of 78% nitrogen makes much sense (I hope). It’s no different with carbon. Plants and animals perpetually cycle carbon in their bodies, soil, and atmosphere. We must have a form of agriculture where more carbon is being put back into the soil (in the form of organic matter), but we mustn’t forget other nutrients that are just as important.
Nutrient cycling is a very diverse and complex topic in and of itself. There were many rabbit holes I could’ve gone down, but that would’ve taken far, far too much reading time for you and too much writing for me. Maybe in some other newsletter, I’ll discuss such topic[s]. Your thoughts, maybe, would be appreciated on that.