(The following is from my monthly newsletter. This series began in March 2022 and has continued for nearly a full year, with its final installment in February 2023. Below is the “better” edited version from what I originally emailed to my followers.)

With the help of the flow of solar energy as well as water, nutrients can be cycled.

What is nutrient cycling, you ask? It’s basically a movement of nutrients from one organism to another, in a complex, biological 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, nor is as noticeable as the water cycle. However, it is also a perpetual cycle that never ceases, and that 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 own 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 that are in there. Pay most attention at the minerals, like those mentioned above. Vitamins are much, much harder to track because they are biochemical compounds that are synthesized by micro-0rganisms, and readily break down or denature after a certain time, or under certain conditions.

The Circle of Life

Aside from the 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 has existed before birth and continues onwards after death.

Nutrients are cycled when animals eat other animals, animals eat other plants, and plants “eat” the remnants of animal carcasses, the latter in an indirect manner. Nutrients are also cycled when animals and plants die. Animals don’t just keep all the nutrients they eat to themselves, however. 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 a great deal of 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 important 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, and so the cycle continues.

It’s Not Independent

The nutrient cycle depends on “decomposing sunlight” in order 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 vitamins that are fat-soluble). 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 which maximizes the ability for minerals and nutrients to cycle.

What about rocks? Even so, with the power of water that is able to 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 other individual nutrients that a plant or animal can take up or in, respectively, based on what concentrations are already there. Sometimes imbalances occur causing toxicities or deficiencies. For example, calcium is influenced by or influences phosphorus, magnesium and potassium, and other elements. Hydrogen affects life and other mineral compounds in the form of acidity, neutrality, or alkalinity.

Finally, the speed to which nutrients move from one organism to another or from the soil to plants and onward varies from mineral to mineral. Bioavailability is dependent on the types of soil biology available to convert certain minerals from inorganic to organic, plant-available form. Phosphorus, for example, is slower to move in the soil compared with 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 go without discussing the importance of plant residue or, as my university range prof always called it, “litter.”

A couple of months ago, I discussed the importance of litter as a means to cover 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 serves the function of returning nutrients to the soil. How?

Litter must break down in order to return nutrients back into the soil. The result of this decomposition releases those nutrients to be made useable again by soil micro-organisms, other plants, microscopic animals, and others. Without this decomposition, the remaining litter remains as is, oxidizing by weathering. Not much life can make use of “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.

1. Mechanical Forces
2. Biological Forces
3. Other Forces

Mechanical forces are forces that actively shear, crush, pulverize, shred, or chop up the dead plant material. Trampling by the hooves of large (and small) herbivores counts as a mechanical force, as does hail or heavy rains. Other animals that have 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, to a much lesser degree.

Biological forces are the activity of “all creatures great and small,” pardon the James Herriot pun. Small 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 are 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 other 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.

Fire works very quickly to “break down” litter but with the heavy cost of a lot of smoke and carbon dioxide emitted to the atmosphere. Fire also has the tendency to almost to completely destroy all other life that is on that piece of land. While fire is good in some respects, and using it largely depends on your context, it’s not the most ideal force to be using in the cycling of nutrients.

Oxidation of litter is probably just as bad, 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 also from getting down. (I’ve also seen it keep too much water at 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 discussion around community dynamics, we can see that our management still plays a big role in not just capturing sunlight and creating an effective water cycle, but also in the cycling of nutrients. You probably noticed I negated to talk about carbon cycling, and that’s due to one reason: carbon cycling is really not much different than discussing how other nutrients cycle, like nitrogen for instance. Capturing nitrogen from an atmosphere made up of 78% nitrogen just makes a lot of sense (I hope). It’s no different with carbon. Carbon is perpetually cycled by plants and animals, in their bodies, in the soil, and in the atmosphere. Absolutely 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, many rabbit holes I could’ve went down, but that would’ve taken far, far too much reading time for you, and way too much writing for me. Maybe some other newsletter I’ll discuss such topic[s]. Your thoughts, maybe, would be appreciated on that.