“You have to make the time for proper soil health.”

This was the thesis of Dr. Heather Darby’s presentation at a recent workshop in Fort Plain, NY. Darby is a soil and agronomic specialist with the University of Vermont.

It’s easy to forego the soil health part of your program – especially when you’re busy and stretched thin, she noted, but intentionally trying to balance all of the components needed for strong soil health will produce far better dividends for your farm operation than simply trying to maintain and hope for the best.

“We don’t always negotiate all of the necessary components in conjunction with each other,” Darby said. “They are all crucial for healthy, highly-productive soil. Sometimes you can have a healthy soil, but that doesn’t necessarily equal maximum yields. When you’re looking at this equation, you have to incorporate an agricultural management perspective and a knowledge and perspective on soil health. You have to manage both.”

She noted that healthy soil should have sufficient nutrients, good tilth (its physical suitability to support plant growth), sufficient depth to allow good root growth, good water storage and drainage and low weed pressure. It should, ideally, have a low occurrence of plant disease and a low population of parasitic organisms in favor of a high population of organisms that encourage plant growth.

It needs to be resistant to degradation through erosion and the like, she added, noting some of the recent rain events experienced in the Northeast.

Soil health for grasslands depends on a variety of factors including root growth, grazing patterns and plant species diversity. Actually, “the development of excellent soil porosity and our levels of soil organic matter relates directly to two factors: root systems being able to grow to excesses of 12 inches or more and the area being home to a biodiversity of species,” Darby said. “How do we make this happen?”

She responded by focusing on the lifecycle of soil organic matter (SOM) and the impact it has on these health components.

SOM drives much of the soil’s function, though it only comprises about 1% to 6% of soil mass. It incorporates living matter (10% to 20% of the total), active matter (“dead,” according to Darby – 10% to 20%) and humus matter (“very dead” – 60% to 80%). The varied SOMs feed on each other in a lifecycle that is hugely important for organic farms – especially those that don’t add their own organic fertilizer. A good ratio is necessary.

“Soil organic matter is your ‘fertility bank.’ That doesn’t mean you stop adding to it. Every time you’re harvesting, you’re pulling nutrients out of that field. You have to at least replenish what you’re taking away,” Darby said. If levels of a particular mineral are low, you need to add that specific mineral.

A lot of the living organic matter in the soil will be naturally occurring as fungi, bacteria and local organisms break down plant structures – but you need to feed them what they need to accomplish this successfully.

Intentionally pursuing balanced soil health

Dr. Heather Darby (UVM) conducts a workshop on soil health. Photo by Andy Haman

“If you’re only adding one type of organic matter all of the time, you’re going to create a system that’s not really that diverse. You need to be diversifying this material,” Darby said. She gave the example of utilizing manure from different contexts (barnyard, chicken coop, etc.), and the varying nutrients and organic life it would bring with it.

Soil testing is clearly helpful for evaluating these levels. Darby touched on two tests in particular: for phospholipid fatty acids (PLFA – “a snapshot of soil community structure and abundance”) and for nematodes, which would highlight common harmful and pathogenic nematode activity in the soil.

Some examples of beneficial organism life would be good bacteria, fungi, mites, earthworms, moles and springtails. “Fungi break down harder crops – bacteria break down the easy stuff,” she noted.

The step below living SOM is “dead” or active soil matter, comprised of recently deceased soil organisms and crop residue which energize and provide nutrients to sustain living soil organisms. This “active carbon” provides a lot of the soils’ charge. The more charge your soil has, the greater its capacity to hold onto nutrients.

For example, a clay might have a charge of 15 to 20. A sand might only have a 3, and therefore is far less desirable from a soil health standpoint.

In a healthy soil environment, all of the types of SOM work together to form soil aggregates: humus (“very dead”) material bonds with partially broken-down organic matter (plant roots, fungal threads, bacterial gels and earthworm feces) to form glues that hold soil particles together and creating a solid soil structure.

Aggregated soils result in better water drainage, as there is good channel space for filtration amidst the particulate structure. Non-aggregated soil crusts on the surface after aggregate breakdown, resulting in runoff versus absorption.

Darby also touched on the need for good soil cover – “armor your soil!” Good groundcover in your fields is important to shield your soil. The proper temperatures are imperative for this formula to work and this lifecycle to perpetuate the way it is supposed to.

She noted that microbial activity goes dormant in the heat (90º and higher), intrinsically shutting everything down.

In closing, “we think of biodiversity on three levels: genetic, species and ecosystem. All three are vital for your operation and apply directly to your farm,” Darby said. “Feed the soil with diversity – no one likes to eat the same thing all of the time and that includes soil life.”

by Andy Haman