Our soils store water in three forms:
- As colloidal films surrounding individual soil particles or groups of particles. This is the form in which growing plants extract most of their water from soils.
- As underground streams called aquafers. This is the form in which mankind extracts liquid water from soils.
- As vapor in the form of the 100% relative humidity air that fills the pore spaces between individual soil particles. This is the form that mankind has yet to recognize and exploit.
This paper examines the potential gains to mankind from learning to exploit vapor forms of soil water. Indeed mankind’s very survival on planet earth may depend on this recognition taking place.
Humans have only been able to sustain themselves from the water resources offered by soils while their demand for soil water has been less than its available supply. But continued population growth is fast approaching a “tipped point” that will force mankind to look to other forms of soil water to nourish the plants that make up 90% of the food that we eat. By 2050, it is estimated that the global population will reach 10 billion.
Feeding More Than Just the Family
Industrialization of plant-based food production began in earnest when John Deere began making steel moldboard plows in 1837. Numerous ancient civilizations had used various forms of wedge-shaped digging devices for “survival agriculture” well before the advent of steel moldboard plows. But Deere’s implement allowed a relatively small number of arable farmers to feed a much larger number of non-farmers who could focus on other things than food production.
Ironically, Deere ceased production of steel moldboard plows in 2024 for equally good reasons. In the meantime, the moldboard plow had fed the industrial revolution. And the manpower advantages of such interdependence among people became so strong that no one at the time thought to question if there were any downsides to plowing.
Even the dust storms of the 1930s were only partially blamed on plowing, which had oxidized soil organic matter (SOM) and turned soil into dust. What people did not (and many still do not) understand is that soil aeration also allows pore-space soil water vapor to escape, which in turn removes life-support for the 6 billion soil microbes that otherwise inhabit every full cup of healthy undisturbed topsoil.
“Vapor water not only facilitates seed germination and seedling emergence, but energizes the soil microbiology…”
These microbes produce glue-like substances that bind soil particles together. At the same time, repeated tillage of arable soils oxidizes the carbon content of soil organic matter into dioxide (carbon dioxide (CO2). This is discharged into the atmosphere where it accounts for about 20% of the total CO2 in the global atmosphere at any one time.
Amazingly, mankind’s ignorance of the role of soil water vapor in topsoil (referred to as the rhizosphere) still persists today except among a small number of well-informed soil biologists and farmers. But recent advances in the practice and design of tools to undertake “low-disturbance no-tillage” have offered pathways forward that mankind has yet to take full advantage of.
No-Till’s Biggest Mistake Regarding Soil Water
In its broadest sense, no-tillage is the practice of growing crops in soils that have not been plowed or otherwise tilled or physically disturbed. The practice has evolved slowly since it was first used on a field scale in the 1950s and its soil-and-time-conservation advantages were recognized.
Mankind’s biggest mistake when trying to master the practice of no-tillage has been to assume that seeds obtain all of their soil water from physical contact between the soil and the seeds that are embedded in it. As a result, designers of no-tillage drill openers have concentrated on substituting localized strip-tillage, minimum tillage or zone tillage in otherwise untilled seedbeds in the erroneous belief that seeds need to make physical contact with disturbed soil in order to absorb sufficient water to germinate while the rest of the seedbed remains untilled.
In the 1980s, scientists began evaluating experimental no-till openers that create inverted-T-shaped seed slots in which physical slot disturbance was deliberately limited to a sub-surface soil layer beneath an otherwise minimally-disturbed surface mulch of dead or dying vegetation.
Only then was mankind able to retain water vapor in the pore spaces occupied by newly-sown seeds in the rhizosphere as if the soil had never been disturbed in the first place.
This vapor water not only facilitates seed germination and seedling emergence, but energizes the soil microbiology that exists in the same environment. Ironically, once the seeds have germinated, their roots rely heavily on seed-to-soil contact for nutrient uptake. This occurs by natural root-exploration of untilled soils that extends well beyond the seeded rows created by mankind.
A huge range of beneficial soil microbes (including bacteria, protozoa, fungi and viruses) thrive and interact with one another in the high-humidity rhizosphere. These microbes ultimately determine the regenerative qualities of undisturbed soils along with macro-soil fauna such as earthworms, nematodes and insects.
Vapor Water is Critical in the Soil
Understanding the role of vapor water in soils opens the door for mankind to add specially bred or selected microbes into the rhizosphere that are the predators of known soil pathogens and pests. Still other microbes bio-release nutrients bound up in soil minerals and in so doing have the potential to reduce our reliance on applied inorganic fertilizers and broad-spectrum pesticides.
These are the building blocks of mankind’s future soil-based food supplies. But they will only become widespread if mankind learns to design and use a new-generation of drills capable of performing low-disturbance no-tillage. This will allow no-tillers to fully exploit the water vapor contained in the “dirt beneath their feet.”
As a bonus, low-disturbance-no-tillage in conjunction with cover cropping adds elemental carbon to arable soils rather than removes it, which conventional tillage has done for centuries.
As an example of the ability of soil pore-space water vapor to feed mankind, scientists at the New Zealand Foundation for Arable Research in Geraldine, New Zealand have obtained wheat yields in excess 250 bushels per acre using an inverted T low-disturbance no-tillage drill. This represents a 60% increase on the already-high average wheat yield listed by the Food and Agriculture Organization for New Zealand 150 bushels per acre, which was previously regarded as the highest average wheat yield by country in the world.
