Mastering Soil Health Elevates Farm Productivity, Sustainability (part 1)

by Dennis Pollock– Western Farm Press

It seems in recent years it has become all the rage to make sure that the dirt under our feet – and plants or trees – is healthy in order to sustain farming.

Soil health was the chief topic at a University of California soil health field day held at Five Points, attended by about 200 people including boots-on-the-ground farmers and researchers.

Jeff Mitchell,  University of California (UC) Cooperative Extension cropping systems specialist at Fresno County, has been toiling in the trenches – literally – for some 20 years, seeking to illustrate the value of cover crops, and no or low-till agriculture.

At the workshop held at the UC West Side Field Station, Mitchell had trenches to showcase, pits that showed differences between conventional and no-till farming. Speakers on hand discussed some of those differences.

Improved soil health

Mitchell, the growers, and others emphasized that managing for better soil health was best achieved by minimizing soil disturbance, maximizing the diversity of plants in rotation or used as cover crops, keeping living roots in the soil as much as possible, and keeping the soil covered with plants and plant residue at all times.

“I have something growing in the ground 365 days a year,” said Scott Park with Park Farming in Meridian in the Sacramento Valley. “Having roots in the ground is 10,000 times better than adding biomass.”

Making money while saving the Earth

Park, a highly diversified farmer, says he moved to a no-till, cover crop approach about 30 years ago after realizing that his tillage efforts were costly. He subsequently became “sensitive to the soil” and adapted no-till and cover crops, not because he was driven to be environmentally sensitive but because his newfound way of farming “was making me a lot of money.”

His approach means using few if any nutritional inputs, he said, and he uses less water. Moreover, he shared that his insect pest problems – notably from leafhoppers in processing tomatoes – are significantly lower.

Just as Mitchell stresses that there is a learning curve to making the switch to no-till and cover crops, Park has learned he needs to “be thoughtful” in cover crop selection. “Cereals don’t break down easily,” he said.

Jesse Sanchez with Sano Farms in Firebaugh said, “Soil health is the way to go, but it takes time to learn. Cover crops benefitted our operation 100 percent.”


Yellowing of Crop Leaves? It Could Be Iron Chlorosis.

Iron chlorosis is a yellowing of plant leaves caused by iron deficiency. However it is not always a true iron deficiency but rather an iron tie-up in plants and soil. Yellow leaves indicate a lack of chlorophyll, the green pigment responsible for photosynthesis (sugar production) in plants.

The causes of iron chlorosis are complex and not completely understood. It could be a deficiency in the soil or the plant or an iron tie-up in the soil or plant. Many reactions govern iron availability and make iron chemistry in the soil complex. Iron chlorosis generally occurs in calcareous soils with a high pH. Even though these soils have plenty of iron, the high pH causes chemical reactions that make the iron unavailable to plant roots

Plants that are native to high pH soils don’t illustrate symptoms of iron chlorosis, because they have evolved to use iron efficiently and can obtain iron from the soil. Recent research has discovered that bicarbonates (HCO3) play a major role since they are readily produced in high pH soils, especially when moist conditions limit iron availability. Even in alkaline soils, bicarbonate is much higher in the calcareous soil than in the non-calcareous soil.The causes of iron chlorosis are complex and not completely understood. It could be a deficiency in the soil or the plant or an iron tie-up in the soil or plant. Many reactions govern iron availability and make iron chemistry in the soil complex. Iron chlorosis generally occurs in calcareous soils with a high pH. Even though these soils have plenty of iron, the high pH causes chemical reactions that make the iron unavailable to plant roots

In calcareous soils, bicarbonate inhibits mobilization of accumulated irons from roots to foliage and affects availability of iron in the soil by buffering soil pH. When high bicarbonate irrigation water is applied, iron deficiency is enhanced because bicarbonate is supplied to the soil. The adverse effects of high bicarbonate levels are exacerbated in saturated soils, very dry soils, or compacted soils, where bicarbonate levels increase, leading to diminished root growth and nutrient uptake.

Gypsum can help remediate iron chlorosis. This is because gypsum reacts with bicarbonate to form calcium carbonate (CaCO, or lime) decreasing the amount of bicarbonate in the soil that affects iron uptake and iron availability.

Daniel Davidson, Ph.D. Agronomist


By Mahdi Al-Kaisi

We need to figure out how to reward farmers for using conservation practices to build soil health.

The term “economics of soil health” has been used frequently in an attempt to quantify and validate the value of improving soil health. The traditional thinking about assigning dollar values to soil health metrics, which are many, can be very challenging, and it is easier said than done.

One of the challenges in putting a dollar value on soil health is the improvement in soil health is a long-term process. Realizing an immediate economic return can defeat the purpose for those who are looking for a quick fix of the long-term sustainability of soil health and its cumulative effects on soil productivity.

It is imperative to view soil health economics in two ways: include the system role in reducing operational costs along with the system effects on improving the soil’s biological, physical and chemical attributes as main components of soil health metrics. These two benefits are mutually interconnected.

Practices improve soil health
The drivers for improving soil health are many, but we can name a few including the conservation systems illustrated in the chart below. These drivers are no-till, the use of cover crops, crop residue management, buffer strips, etc. Therefore, to quantify the economic value of improving soil health, the focus should be on the outcomes and impacts of these practices used in a system approach for return on investment (ROI).

It has been documented by many long-term studies that conservation systems such as no-till, strip till, cover crops, and filter strips (i.e., prairie strips) have significantly reduced input cost per acre and provided ecological services, such as the reduction in soil erosion and soil nutrient loss. In a long-term tillage and crop rotation study in Iowa, over 10 years of results suggest that input cost with conventional tillage for corn production was 7.5% and 5.7% greater than that with no-till and strip till, respectively.

In the meantime, no-till and strip till practices have been documented to have a greater impact on improving the soil health metrics of soil biology, soil water processing (i.e., infiltration rate), and the soil physical attributes of aggregate stability and water-holding capacity, to name a few.

Sustainability is profitable
Essential to soil health and crop productivity is a shift to a system that provides economic incentives in terms of change in the cost of operations, such as labor, fuel, machinery, chemicals, etc., yet provides ecological services reflected in the improvement of soil health metrics. This approach will potentially minimize risks during severe climate events (both dry and wet).

The link between different components of the system highlights the economic value of improving soil health through improvement in soil carbon sequestration and water quality. Thus, improving the soil ecological system, reducing input costs and stabilizing crop productivity by moderating the severe impact of climate variability events during a growing season are the best economic indicators for improving soil health with a lasting economic impact on sustaining a system’s productivity.

New thinking needed
New thinking needs to emerge to address the economic value of soil health by protecting and sustaining the soil system from any long-term degradation resulting from destructive and imbalanced management practices such as intensive tillage, which is the leading cause of soil and water quality degradation in the Midwest. This new thinking for soil health economics needs to be linked to the system effects on the ecological level. Furthermore, those who have been pioneering conservation systems for many decades need to be recognized in the agriculture marketplace, such as crop insurance.

To encourage the adoption of soil health practices, there needs to be a mechanism, which reflects the economic benefits or incentives of soil health by linking crop insurance rates, for example, to the improvement in soil health as currently advocated by some economists. It has been documented that conservation systems improve soil health and reduce input cost. Crop insurance can be used as a tool to provide incentive to encourage emerging adopters and existing practitioners of conservation systems to improve and sustain soil health and ROI.

Soil health is an indicator of system performance in rejuvenating and enhancing the soil’s ecological, environmental and economic services. Its economic value is an integral part of the system’s returns and benefits. In conclusion, the case for soil health economics has to be articulated in a system approach that reflects the mechanism by which we develop and maintain healthy soil as the foundation for a productive and sustainable agriculture.

Al-Kaisi is a professor in the agronomy department at Iowa State University.






Agricultural Limestone

(also called agricultural lime, ag lime, biolime, garden lime, or simply “liming”)





Chemical names:


Calcium carbonate

Calcium magnesium carbonate



Calcium sulfate dihydrate


Chemical formulas:









Common names4 used in agriculture, and purity or % calcium carbonate equivalent (CCE):

Ground limestone

(up to 100% CCE)



(80-110% CCE)



(up to 100% gypsum equivalent)

Uses in agriculture: 1. Raises pH of acidic soils (generally when pH  6) by increasing exchangeable calcium and neutralizing hydrogen ions.


2.  As a source of calcium and/or magnesium in low pH and low Ca and Mg areas.  Note: agricultural limestone is always 150 times less soluble than gypsum.


3.  May slightly improve water penetration in acidic soils (pH  6) but the improvement decreases as pH rises. No improvement at pH  7.

1.               1. Amends and reclaims soils high in destructive sodium and magnesium.


2. Improves water penetration at the soil surface, and infiltration through the entire profile.


3. Is necessary when irrigation water and soils are low in total salts.


4. Counteracts acidity in subsurface soils.


5. An excellent fertilizer source for calcium and sulfur.

1  Dr. Arthur Wallace, former Professor of Plant Physiology at UCLA, founder of Wallace Laboratories, and one of the most respected Soil Scientists of the 20th century, listed forty benefits for using gypsum with agricultural soils.  http://us.wlabs com/

2  dolomite can have a CCE greater than 100 percent since each molecule of magnesium carbonate is lighter than calcium carbonate

3 note: the proper name for dolomite is “dolomite (or dolomitic) limestone”

4 other less commonly used liming materials include sugar beet lime, hydrated lime, burned lime, shell meal, calcium silicate, power plant ash, and cement kiln dust


By Brent Rouppet, Ph.D.

(Part 2 of a 3 Part Series)

Gypsum. Gypsum is invaluable is since it the only natural product on Earth that serves as an (1) amendment, (2) a soil conditioner, and (3) a fertilizer; and this unique and essential product should not be confused with limestone, dolomite, and other liming materials.  Gypsum typically is neutral with a pH.

  • Improves water use efficiency (WUE). Twenty-five to 100% more water is available in gypsum treated soils vs. untreated soils; therefore, less irrigation water is required to achieve the same results.
  • Improves soil structure and loosens compacted soils. Reduced water infiltration causes ponding and runoff and can waste irrigation water. Improved soil structure reduces erosion and soil crusting.
  • Amends and reclaims soils high in destructive sodium and magnesium. Sodium and magnesium (to a lesser extent) act the opposite of calcium in soils by deflocculating structure and reducing water and air movement, and root growth. Preferably, here should to be 16 times more calcium in the soil than sodium, and 8 times more calcium than magnesium.
  • Counteracts acidity in subsurface soils. Calcium moves into the subsoil displacing aluminum and other acidifying ions from the exchange complex.
  • Improves water penetration at the soil surface. Gypsum is necessary when irrigation water doesn’t contain many minerals and when soils are low in total salts.
  • An excellent fertilizer source for calcium and sulfur. There are 16 nutrients required or essential for plants. Calcium and sulfur are two of the essential nutrients.

Growers must be aware of which soil amendment product is needed for application for each specific use.  Limestone and dolomite are used to amend soils that are too acidic for optimum plant growth and production; and gypsum is used primarily to correct soil structure-related problems, and to help with any water penetration problems.

From the standpoint of plant nutrition and as a soil conditioner or soil amendment, gypsum uniquely helps soils be more productive and more fruitful than any other single product on earth. Worldwide gypsum’s usage is largely underutilized, yet routine and frequent application of this essential amendment is required for the sustainability of all irrigated soils.


 By Brent Rouppet, Ph.D.

(Part 1 of a 3 Part Series)

There are two key soil amendments in agriculture: (1) gypsum (calcium sulfate dihydrate [CaSO4 H2O]), and (2) liming materials such as limestone (CaCO3) and, dolomite ((CaMg(CO3)2). Liming materials are applied to neutralize soil acidity, but in situations where Ca is required without the need for correcting soil acidity, then gypsum is necessary.

These soil amendments should never be confused. Routine and frequent application of gypsum is required for the sustainability of all irrigated soils1; and while limestone, dolomite and other liming materials are necessary to neutralize soil acidity problems, improper usage of these liming amendments will actually result in harm to crops and plants.

The differences between gypsum and liming materials, and their uses in agriculture: 1. Limestone, dolomite, and other liming materials. Liming products are used and necessary in agriculture when the pH of the soil becomes too acidic for optimal plant growth and production. For most soils worldwide optimum pH is 6.2. At this pH the essential plant nutrients are most available; so in most cases in agriculture we strive to maintain a pH as close to 6.2 as practical.

If the soils become too acidic (have pH values lower than 6.2) then limestone, dolomite, or other liming products are applied to bring the pH back to the optimal range for crop/plant growth and production.

An example of the chemical reaction:

CaCO3 (limestone) + CO2 + H2O + 2H+ (acid) Ca2+ + CO2 + H2O

Acidic Soils:

• Soils become acidic when they are leached, especially in areas of higher rainfall. The more leached the soils are, the more strongly acidic they are.

• Strongly acidic soils have (1) few basic cations (calcium, potassium, magnesium and sodium) available in the root zone; (2) higher amounts of aluminum, hydrogen, and manganese; and (3) have lower amounts of more easily leached nutrients: sulfur, boron, zinc, molybdenum, and chlorine.

• Levels of toxic aluminum and manganese iron increase as pH levels do down.

• Most microbial processes, including nitrogen fixation, are slowed down by strong acidity.

Limestone, dolomite and other liming materials should never be applied to soils when the pH levels are above 7.0. At higher soil pH values the carbonate in limestone and dolomite will actually burn the crops, and even cause plant death in more severe cases.

The grower must be aware of which soil amendment products are needed (and how much) for application for specific uses to maximize crop production, and not harm plant growth and production.

Note: Dolomite is also used worldwide as a fertilizer source for magnesium (and calcium), but should only be used when soil pH values are less than 7.0.

Again, at pH values higher than 7.0 the carbonate in dolomite will actually burn the crops. Since limestone and dolomite are 150 times less soluble than gypsum, they generally are not a preferred source of calcium as a fertilizer.


Western Farm Press. 15 February 2016.  U.S. and Chinese officials appear to have reached an agreement on a phytosanitary protocol for the shipment of American-grown milled rice into Chinese ports, according to a statement by the USA Rice Federation.

Most trade exports believe China has been importing more rice than it reports with most of the foreign-grown rice coming from Cambodia, Thailand and other countries along its southern border, but none from the U.S.

“The challenge now is to move from agreement to shipments,” said USA Rice Federation CEO Betsy Ward, who, in the past, has described the long-running negotiations as “complex,” and involving issues that seemed to have little to do with actual pest issues faced by rice producers in the U.S.

“This extraordinary agreement has been a long time coming, and I commend the U.S. negotiators and USA Rice for sticking to it and getting us a phytosanitary protocol that while more complicated and detailed than any other rice protocol in the world, is something both industries appear able to make work,” said Dow Brantley, USA Rice chairman.  read more


PHYSORG. 12 January 2016.  Scientists have wondered for years how legumes such as soybeans, whose roots host nitrogen-fixing bacteria that produce essential plant nutrients out of thin air, are able to recognize these bacteria as both friendly and distinct from their own cells, and how the host plant’s specialized proteins find the bacteria and use the nutritional windfall.

Now a team of molecular biologists led by Dong Wang at the University of Massachusetts Amherst, working with the alfalfa-clover Medicago truncatula, has found how a gene in the host plant encodes a protein that recognizes the cell membrane surrounding the symbiotic bacteria, then directs other proteins to harvest the nutrients. Details appear online in the January edition of Nature Plants.

As Wang explains, plants often recruit microbes to help them satisfy their nutritional needs, offering the products of photosynthesis as a reward. A process used by most land plants depends on a symbiotic relationship with mycorrhizal fungi. These form structures known as arbuscules that help plants capture phosphorus, sulfur, nitrogen and other micronutrients from the soil. This method is akin to scavenging, Wang says, because the amount of nitrogen available in soil is quite limited.

By contrast, the less common process, found mostly in legumes, goes one giant step further: it uses bacteria called rhizobia, which live in root nodules and fix nitrogen from the air and make it into ammonia, a plant fertilizer. Symbiosis with rhizobia means legumes can make ammonia by fixing nitrogen in the air, which at 78 percent of the atmosphere, is “essentially limitless,” the biochemist adds.

Thanks to this feat, legume plants can get as much nitrogen fertilizer as they need, rather than relying on often scarce nitrogen in the soil. This is why beans are so nutritious, Wang notes. “The next time you eat your tasty tofu or edamame, you have those little bacteria, and their ‘marriage’ with legumes to thank.”

“Talk to anyone in our field, and the dream is to make it possible for our crops that can’t fix nitrogen to get that ability,” Wang suggests. “This discovery moves us one step closer. Beans are special, but what our result says is they are not that special because some of the basic infrastructure is already there in plants that use arbuscular mycorrhizal fungi instead of nitrogen-fixing bacteria, which no one understood before.”
Read more at:


Growing Produce. 8 January 2016.  International trade is a major factor in the American agricultural economy. A key player is China. In fact China’s impact on slowing growth on trade and agriculture is a session topic during the 2016 USDA’s Agricultural Outlook Forum.

Over the last two decades, China’s economic prosperity and increased consumer demand for food has significantly contributed to the record growth in U.S. agricultural exports. From fiscal year (FY) 2000 to FY 2015, the value of U.S. agricultural and related exports to China rose from $1.7 to $25.9 billion. Currently, nearly 17% of all U.S. agricultural exports are destined for the Chinese market. These export figures highlight the critical importance of the U.S.-China trade relationship for U.S. agriculture and underscores the U.S. interest in China’s ability to maintain a strong and stable economy.Several U.S. agricultural sectors have capitalized on the market opportunities created from China’s economic growth. Traditionally U.S. exports to the country were dominated by land-intensive bulk commodities that were processed for domestic consumption or re-exported. Recent increases in Chinese consumer purchasing power and improved standards of living have generated new demand for luxury items and ready-to-eat foods.

Looking forward, many of the macroeconomic conditions traditionally signaling long-term growth and trade expansion readily exist in China. An increasingly urban population, a burgeoning middle class, and higher disposable incomes have increased Chinese consumers’ ability to diversify diets and purchase high-value, protein-rich foods. Additionally, growth in China’s food consumption is forecast to outpace its domestic agricultural production by more than 2% per year between 2015 and 2020, resulting in an increased demand for food imports (IHS Global Insight).

U.S. trade with China has been rewarding; however, China’s economic slowdown, subsequent reforms, and recent decline in U.S. exports to China have raised legitimate concerns among agricultural stakeholders about the potential impact to U.S. exports in the near and distant future. China’s Gross Domestic Product (GDP) growth is projected to drop to 6.1% in 2016, their lowest level since 1990. Moreover, China is pursuing a variety of economic and regulatory policies that promote agricultural self-sufficiency and protect domestic industries. Finally, whether directly or indirectly triggered by the recent economic slowdowns in China, a majority of U.S. agricultural exporters have experienced severe decreases in sales to the region over the last year. Total FY 2015 U.S. farm exports to China are down approximately $4 billion or 13% from the previous fiscal year and are projected to drop even more in FY 2016. Collectively, these events have created uncertainty within the global agricultural marketplace and have caused broad speculation on the future of U.S. trade with China.


Scientific American 6 January 2016. Nathan Cude pulls open the top of a white Tupperware container labeled Q8R, which holds one of the hundreds of samples of American farmland he’ll handle in a year. The dark brown soil inside looks lifeless, but the microbiologist at Novozymes smiles as he utters one of his favorite lines: A spoonful of soil contains about 50 billion microbes, representing up to 10,000 different species. The number of organisms in the container surpasses the number of people who have ever lived on Earth.

Communities of soil-dwelling bacteria and fungi are crucial to plants. They help plants take up nutrients and minerals from the dirt and can even extend root systems, providing more access to food and water. They also help plants grow, cope with stress, bolster immune responses and ward off pests and diseases.

Now scientists at agricultural companies are digging through the dirt, like prospectors panning for gold, to find the exact microbes that make specific crops grow better. Agribusiness firms Novozymes and Monsanto are leading the way by coating seeds with microbes, planting them on farms across the U.S. and harvesting the crops to see how they fared. The two companies, through their BioAg Alliance, have just concluded the world’s biggest field-test program of seeds laced with promising microbes. This past autumn they harvested a variety of crops, planted using seeds with more than 2,000 different microbial coatings, grown in some 500,000 test plots from Louisiana to Minnesota, and they have been busily analyzing the outcomes. They will announce early results today. But they gave Scientific American a peek at their operations, and their aspirations, prior to releasing any findings.

Ultimately, such microbial agricultural products could significantly reduce fertilizer and pesticide use, easing the burden farming imposes on the environment and potentially helping a farmer’s bottom line by reducing costs or increasing crop yields. The research is the beginning of an ambitious movement to replace chemistry in agriculture with microbiology.

Field trials are the key. “There is nothing that translates a greenhouse result to a field result,” says Thomas Schäfer, vice president of bio-ag research at Novozymes, and Cude’s boss. “Because the field is so complex, we have to test [seeds] in the field directly.”

A growing need
The world’s population is predicted to reach nine billion by 2050. With more mouths to feed, agricultural yields will have to nearly double. Climate change isn’t helping: droughts, floods, rising salinity and soil erosion are creating harsher growing conditions. Many pests and pathogens are developing resistance to pesticides. Chemical fertilizers only partly address the problem, and some studies show they contaminate groundwater, possibly contributing to human illnesses, and amplify harmful algae blooms in rivers and oceans. Scientists are hoping microbes can provide a viable alternative.

That solution could also alter the economics of big ag companies. Today the market for agricultural biologicals, such as natural pest controls, plant extracts and beneficial insects, is about $2.9 billion a year [updated Jan. 7, 2016]—a mere fraction of the $240 billion brought in by traditional fertilizers and pesticides, according to the alliance. Monsanto thinks the microbial market could grow substantially. Microbials have faster development cycles and fewer regulatory hurdles than other agricultural products, which can take 10 to 14 years to move from idea to market. And if widespread use lessens dependence on fertilizers and pesticides, that could ease public wariness of industrial farming.

The notion of bio-agriculture isn’t new. In 1888 the Dutch microbiologist Martinus Beijerinck discovered that the roots of leguminous plants were inhabited by a bacterium called rhizobium, which could take nitrogen from the air and convert it into a form the plants could use. Farmers and gardeners have been sprinkling packets of powdered rhizobiaon their peas and beans ever since. One by one, other microbes have been transformed into products, like biofungicides and biopesticides. But it wasn’t until recently that new DNA-sequencing tools allowed researchers to see the vast, complex microbiome, known as the rhizosphere, living in, on and around plant roots. A 2012 report written by the American Academy of Microbiology, titled How Microbes Can Help Feed the World, argued that tapping into this resource could generate products that “increase the productivity of any crop, in any environment, in an economically viable and ecologically responsible manner.”

The tricky part is figuring out which of the billions of members of the rhizosphere to go after first. Novozymes sends out teams of researchers to collect soil samples from private farms, which they bring back to the company’s labs in Research Triangle Park, N.C., where scientists like Cude process them. Although each sample might contain billions to trillions of microorganisms, only about 1 percent of will grow in the lab. Those that do often materialize in petri dishes in a dazzling array of shapes and colors: thin streaks of indigo blue, droplets of mustard yellow, a fuzzy asterisk of charcoal gray, a giant glob of blood red. Each microbe’s genome is sequenced (decoded) and checked against a database of known pathogens; any matches are discarded whereas the rest move on to the next phase.

The researchers test the remaining contenders to see if they could be used as one of two things: inoculants, which help plants take up nutrients, or bio-control products that help protect against disease and pests. One test checks if the microbes help plant roots better absorb nutrients such as nitrogen or break down inorganic soil phosphates so plants can use them. Another test assesses whether the finalists could offer protection against plant diseases or pests. For example, parasitic nematodes cause more than $120 billion in damage to plants worldwide. Jennifer Petitte, a zoologist at Novozymes, shows me a dish writhing with these tiny worms, which are barely visible to the naked eye. She adds promising batches of microbes to the dishes to determine if any can paralyze or kill the nasty pests.

Vials containing the best microbial candidates travel down the street to another Novozymes laboratory, where they are grown in large flasks filled with various formulations of rich broth, ranging from pale yellow to amber to almost black. Bill Throndset, a microbial physiologist at Novozymes, tells me the flasks’ exact contents are a trade secret, “like the recipe for Coca-Cola.” None of the microorganisms are genetically modified or engineered; instead, they are derived and cultured from soil samples. After each batch is cultured in its favorite media, it is cryopreserved and stockpiled, much the same way eggs or sperm are stored in banks. They’ll need to be alive and healthy when spring arrives and they are applied to seeds, so when the seeds germinate they can become part of the rhizosphere as soon as the plant takes root. “We essentially only have one experiment a year, so we have to get it right,” Throndset says.

Shortly before the growing season, the microbes are shipped a Monsanto facility in Saint Louis, where they are sprayed on seeds in big stainless steel bowls, like giant popcorn holders. In 2014 Monsanto planted seeds coated with hundreds of different microbial strains on around 170,000 plots, ranging from three by three to three by 10 feet in size. In 2015 the company greatly expanded the trial to more than 2,000 types of microbes on some 500,000 plots. Beside each test plot, the company planted a control plot with no microbe-laden seeds, creating a checkerboard effect across portions of the U.S. South and Midwest.

More bushels per acre
In October and November 2015 researchers harvested the crops and began crunching the numbers to determine which if any microbes made a difference. Many of the 2,000 coatings turned out to have no effect. But the top five increased corn yields by an average of four to five bushels per acre and soy yields by an average of 1.5 bushels per acre. The early results “look great,” says Jeff Dangl, a scientist at the University of North Carolina at Chapel Hill who studies the plant microbiome and is not involved with the experiments. “However, typically field trials have to run for seven years before anybody believes them. So the jury is still out. After we see several years’ worth of data, then we will have a more complete picture of which microbes are doing what.”

Nevertheless, the alliance says it plans to launch one of the five microbes as a product in 2017—an inoculant based on fungus found in cornfield soil. Novozymes’ Schäfer admits that even with all of the laboratory testing, he and his colleagues are still making educated guesses when choosing which microbes to send into the field. He hopes after multiple rounds of field testing, with top performers returning year after year, that patterns will emerge to help them predict which strains of microbes will benefit specific crops. The alliance will again field-test thousands of strains in 2016.

Unleashing microorganisms into new environments—particularly when the end product is destined for our kitchen tables—can raise concerns, some more valid than others. For example, Dangl says it is possible that messing with the microbial milieu might affect the taste of a particular crop, much like the composition of soil is known to influence the flavor of wine. There is also a risk that seed coatings, like many agents applied to a field, could slough off one crop and contaminate another. Some proponents don’t see a downside to sharing these “plant probiotics,” however, saying they would at best be beneficial to other crops and at worst have no effect.

Gwyn Beattie, a professor of biology at Iowa State University in Ames and one of the contributors to the American Academy of Microbiology report, has been following Novozymes’ efforts for years. She thinks the biggest concern is not necessarily that newly introduced microbes will grow and spread to other crops but rather that they won’t stick around long enough to do their job in the first place. “My analogy is if you throw one person [at a time] into New York City, the vast majority of people you throw in there do not change New York City. Every now and then there is one that will change the world, but it is not very likely to happen,” Beattie says. “It is like that in a microbial community. Introducing organisms rarely has an impact at all, and that’s actually the biggest frustration.” As a result, she argues, there will always be a need for chemical pesticides and fertilizers, but perhaps in smaller amounts as microbes are added to the mix.

The transient nature of the microbiome is one of the reasons Novozymes and Monsanto are currently field-testing microbes coated on seeds, rather than using other applications like sprays or root soaks. Hitting plants when they are germinating and sprouting, even if the effects are fleeting, could put them on track to be healthier as they grow. Although Schäfer would love to find a single blockbuster microbe, his scientists are also beginning to realize that bigger benefits may come from sets of microbes working together. With thousands of species in one gram of soil, the possible combinations are endless. Right now they are testing the species one by one, and they will wait until they have strong enough data on the singletons before testing combos.

Despite the challenges, Schäfer maintains microbes are poised to make a lasting impact on modern agriculture. Existing microbial products such as Novozymes’ Met52, a fungus that limits vine weevils, are already used on millions of acres; if seed coatings take off, that number could jump. The two firms think bio-ag products will be used on up to 500 million acres, or 50 percent of U.S. farmland, by 2025. “Companies like Monsanto, Bayer, Syngenta and BASF are working on microbes because they believe [the technology] has the potential to reduce chemistry and allow us to live more sustainably,” Schäfer says.