By: Becky Garrison
At the Oregon Wine Symposium held in Portland, Oregon from February 11-12, 2020, Dr. David Montgomery, MacArthur Fellow and University of Washington professor of geomorphology, presented his work researching and writing about farming methods that use less fossil fuel, fertilizer and pesticides than traditional farming. In his books, “Dirt: The Erosion of Civilizations” and “Growing a Revolution: Bringing Our Soil Back to Life,” Dr. Montgomery digs into the history of traditional farming methods and how these practices negatively impact the health of vineyard workers, the vigor of the soil and profitability.
Dr. Montgomery advocates that, if we want to feed people in the next century, we need to change agriculture in this century. He cited the United Nation’s 2015 State of the Soil Assessment, which presented a global review of the world’s soils. According to this assessment, each year, the world loses 0.3% of net agricultural production capaci-ty to ongoing soil loss and separation.
“If we play this out for the next hundred years, we are slated to lose about a third of our agricultural production capacity at a global scale. Our population is slated to rise by about a third,” Montgomery said. Furthermore, about a third of the world’s cropland has been degraded to the point where it’s no longer in production.
The History of Soil Erosion
While working on several continents, Dr. Montgomery noticed the connection between the degraded state of soils and the impoverished state of people living in different landscapes. He observed how soil erosion contributed to undermining civilizations around the world, starting with the earliest agricultural civilizations such as Neolithic Europe, Classical Greece, the southern United States Neolithic and more.
In a review of over 1,500 scientific studies, soil erodes at the rate of one inch every twenty years. At this rate, the soil of a large civilization outside major river flood plains depletes in roughly 500 to 1,000 years. Dr. Montgomery described how flood plains like the Tigris and Euphrates bring sediment and silt, tires, school buses and whatever is coming down the river. “These places can maintain balance, as what the plow takes away on average is replenished by flooding. Nature is fixing the damaged of the plow.”
His findings debunk the traditional theory of soil erosion found in environment history textbooks, that deforestation led to erosion, which undermined civilizations. “I found out it was the plow that followed that did it. The villain of this tale is tillage.”
He described soil as akin to a bank account, whereby it is the natural capital that fi-nances civilizations, as it’s used to grow food, wine and everything else people grow from the ground.
According to Dr. Montgomery, the plow leads to soil degradation because, by design, it inverts soil. “It provides incredibly good weed control, which is why it’s often used in organic systems. A plow takes those nasty weeds upside down and makes fertilizer out of them.”
In addition, tillage accelerates the breakdown of the organic matter in the soil by stimu-lating microbial activity. In effect, this draws down the batteries of the soil by degrading its organic matter. Also, tillage leaves the soil vulnerable to erosion until the next crop. If this process goes on for long enough, the soil’s organic matter can deteriorate to the point of impacting the fertility of the land, negatively affecting the health of the crop.
Is Soil Restoration Possible?
“The problem with long-term soil degradation is not that we farm. The problem is the way we’ve been farming. Tillage has been a major destructive element in human histo-ry,” said Dr. Montgomery.
While traditional farming methods account for the loss of a millimeter to a millimeter and a half of soil each year, no-till farming only erodes less than a tenth of a millimeter of soil during the same period.
When Anne Biklé, Dr. Montgomery’s biologist wife, turned their degraded yard into a garden, she added organic matter consisting of compost and mulch. After a decade, their yard went from 1% organic matter to 12% in some places. In their book, “The Hidden Half of Nature,” they attributed this shift to the work done by trillions of micro-organisms that were feeding underground. This zone, called the rhizosphere, is one of the most life dense areas on the planet. Dr. Montgomery described the rhizosphere as “a biological bazaar where microbes and plants trade nutrients, metabolites and exu-dates.” Like any living organism that consumes something, the plants metabolize the organic matter and produce waste products like growth hormones.
Understanding the symbiotic relationships between soil microbiota and plants presents farmers with two very different diets for feeding their plants. The first is the fertilizer diet, where if you give a plant enough fertilizer, even bad soil can produce big yields. How-ever, as Dr. Montgomery assessed, once the plants get all the significant elements they need for growth, they stop investing in their root system. “This means they’re not get-ting as many micronutrients, like zinc and copper, that they need for health, which those microbial partners provide.”
In comparison, growing plants in healthy, fertile soils that have more organic matter to feed those microbes will produce comparable growth. In addition, farmers get the ben-efits of mineral micronutrients and microbial metabolites. Simply put, organic matter produces higher carbon in the soil.
Principles of Conservation Agriculture
To assess if these theories could be implemented on a large scale, Dr. Montgomery visited farms in Equatorial Africa, Central America and all across North America. What he found was a common recipe for rebuilding soils.
First, he said, ditch the plow. Minimal tilling can produce better results, but more car-bon generates when not using a tiller. Second, cover up the soil by maintaining perma-nent ground cover using cover crops and retaining crop residues. Finally, grow diversi-ty. Rotating three to four crops will break up pathogen carryover. In a vineyard, one can achieve this by rotating what’s growing between the vines.
According to Dr. Montgomery, these principles could be scaled up or down, depending on the farm, within two decades. Restoring agricultural soils in this manner can help increase farm profitability, feed the world, help with climate change and prevent envi-ronmental degradation through non-chemical practices.
How Microbes Relate to the Wine World
Discussions about terroir focus on climate and soil; however, Dr. Montgomery sug-gests rethinking terroir in terms of the microbes, which are related to climate, soil and geology. “As we examine the relationship between the soil, the vines and the wines people enjoy, we should think about how the microbial ecology is a big part of that foundation.”
Recent journal articles have begun to cover the landscape of microclimates, including those of a particular vineyard. Microclimates affect the microbes that live in the rhizo-sphere around the roots of grapevines and can carry through to the winemaking pro-cess.
“Microbial abundance and diversity come into play on leaves, roots and fruit, and then carries on into the fermentation process. How you operate your vineyard will determine what you will have in terms of the fungal community,” said Dr. Montgomery. “Hence, understanding the role of microbial ecology is important for rebuilding soil organically, but also in understanding every step of the wine production process.”
Addressing the practicalities of soil management in the vineyard, Dan Rinke, proprietor of Roshambo ArtFarm and Director of Vineyard Operations at Johan Vineyards, said, “If you are continuously tilling and depleting organic matter from the soil, those resultant soils are going to be more prone to compaction. But you can have more resilient soil through no-till systems.”
In Rinke’s estimation, the best way to rotate cover crops is to use a no-till seed drill, which can be rented from some soil and water conservation districts. However, he added that he’d like to see research done in this area to see more comprehensive re-sults using conventional, reduced and no-till means specifically for vineyards.
More research is needed to confirm Dr. Montgomery’s findings and develop and under-stand the implications for vineyards. For biodynamic farmers like Barbara Steele of Cowhorn Vineyard & Garden, carbon farming is not unique. “Carbon cycling in the soil is the basis of successful dirt farming,” she said.
Biodynamic practices include building a fresh compost pile every year and growing plants whose sole purpose is to create carbon. “By increasing organic matter in the soil, we slowly increase the cation exchange capacity or CEC (the measure of the soil’s ability to hold positively charged ions), and thus the carbon cycling in the soil,” said Steele.
For more information about soil health, check out the resources available from the USDA National Resource Conservation Service at…https://www.nrcs.usda.gov/wps/portal/nrcs) and www.dig2grow.com