Soil Health, Wealth, and Wisdom

Written by E. Philip Small on January 30, 2011

"Earley to bed and early to rise, makes a man healthy, wealthy, and wise."

[1639 J. Clarke Parœmiologia Anglo-Latina]

Range managers promote the health of living soil systems as essential to sustained business viability.

The microbial bio-mass of a soil plays a key role in the productivity of grasslands, which in turn determines such things as the stocking rate of pasture and rangelands.

This microbial bio-mass is the living matter within the soil and, according to Andrew Fraase, a graduate student in North Dakota State University’s School of Natural Resource Sciences, they are important in the soil’s productivity. …

“This microbial bio-mass is made up of bacteria, fungi, nematodes, protozoa – really all the living matter in the soil,” he said. “And it’s important because it’s the key to cycling the residue left on the soil and the roots in the soil and transforming that into plant usable nutrients …"

…farmers … are using cover crops to restore degraded soil by increasing the biology under the soil surface. … “As you increase the organic matter in that soil by putting roots into the soil, it’s going to help break up any compaction you have, create more porosity, help the water infiltration rate and the gas exchange,” Fraase said.

Good soil structure also involves good aggregate stability in the soil which, according to Fraase, is a natural formation of soil particles that are cohesively bound together. The binding agent that is key in the soil aggregates is organic matter.

“Why should you care about soil aggregates?” he asked. “Because it’s easier for a plant if it has soil structure, porosity and areas for the roots to move down in the soil profile. This makes it the easier to get to nutrients and water located deeper in the soil profile.” Planting cover crops can also benefit … the bottom line of an operation [as a source of forage].

That forage productivity is a function of soil health is not news. What is news is our evolving appreciation of soil health in terms of a living system. Restored soil is a highly valuable asset in most any setting, and the more intense the land use, the more to be contributed by good soil. Ecological restoration and urban redevelopment have much to gain from the grazing schools of soil husbandry.

There are lots of bits to this puzzle, but when it comes to sustaining life in soil, the energy bit is not to be forgotten. Mulch and compost delivers food energy. Soy bean meal, used to improve soil structure in public turf and playing fields, works similarly.

Cover crops and woody vegetation work to sustain a healthy symbiotic rhizospheric soil community on root exudate rich in food energy. This is a different microbial community than is working on the sloughed root mass, on soy bean meal, mulch and compost – a healthy soil has both a rhizosheric community and a bulk (jargon for outside the rhizospheric soil enveloping the root) soil community thriving in concert.

Gary Jones has posted about this article also, and alludes to a food energy feast available in the context of pulse grazing.

It isn’t just that this reduces compaction, it is also that it pumps biomass into the soil due to “root pruning”. The root systems of many pasture species mirror their above ground growth. When such a plant is grazed it sloughs off an equal amount of its root system, which then regrows apace to the above ground growth. Each “pulse” of grazing in effect pumps another dollop of biomass into the soil thus providing a feast for the micro and macro soil organisms. They convert the biomass into more bugs, but with their lives and deaths mineralize the nutrients making them available to grow more vegetation, and leave a small but valuable residue of humic acids and humates as durably sequestered soil carbon. The more it is done the more that it can be done.

Pulse grazing jolts the system in a good way, and there is a lesson to be learned here that is applicable to urban soils where drastic disturbance often causes the system to loses species diversity. When it comes time to revive soil life, the rate of restoration is slowed by a combination of extremely low population, an excess of predators which restrict re-population, and absent the species diversity needed to share in the restoration dynamic. Pulsed management is an important tool for overcoming this inertia.

Building a diverse palette of soil microbial species in a drastically disturbed site, this is a worthwhile challenge, this is the acme of success. Soil health, wealth, and wisdom.