A High Yield, Low Input Approach to Sustainable Crop & Plant Management
Background of Billions
If you think the roads are crowded on the 4th of July and the malls are unavoidable on Black Friday, think about the number of microbes present in a teaspoon of healthy soil. The number would be about 60 billion, give or take. That is almost ten single organisms for every human currently on this earth.
Healthy soils, as in the words of Jeff Lowenfels, are “Teaming with Microbes.” However the key operative word is healthy. Healthy soils require certain components and capacities such as a source of nutrients (organic matter), cation exchange capabilities, aggregate structure for roots to penetrate, and most importantly, host plants that can support this background of billions of microbes.
What we know About the Soil is Much Less Than What We Don’t Know; but it is a Start.
“We know more about the movement of celestial bodies than about the soil underfoot.”
-Leonardo da Vinci
“To understand the birds, you must first understand the plants. To understand the plants, you must first understand the soil.”
-William H. Durry
For centuries and centuries, farming was a dismal but necessary way of life for over 90% of the world’s population. Those that didn’t farm generally collected rent on the land of those did, rode horses, drank imported wines, or became an officer in the military and went off to war. The peasants that worked the land, planted crops, tended the harvest and then split the spoils of their labors with the landowner, were at the whims of weather, insects, disease and often poor yields. This began to change about a century ago when a brilliant German chemist, Justus Von Liebig made a number of discoveries as to how plants responded to certain elements such as nitrogen, phosphorus, potassium and eleven others. This lead to the commercialization of mining and processing of these elements across most of the agrarian world.
Of all the necessary minerals required for healthy crop production, there was only one very important element that was very difficult to access through mineral deposits and that was nitrogen. But then a couple more brilliant German scientists solved the problem. The “Haber Bosch Process,” developed by Dr. Fritz Haber, and yes, Dr. Carl Bosch, used massive amounts of heat and pressure to extract nitrogen from the atmosphere where it comprises about 80% of the gases that encompass our world. The process was originally developed around 1910 to produce munitions for the German army, but November of 1918, WWI came to an abrupt halt and so did the market for nitrates and munitions. The next obvious market was in crop production, and agriculture has never looked back. For the past century, an abundance of cheaply mined and processed fertilizers has generally improved the diets of mankind. Starvation now only occurs due to political or logistical issues, not because of a shortage of food.
However this revolution toward bountiful crops has come with consequences, mainly too much of a good thing. Nitrate levels in the world are double what they were a century ago, and that additional 50% is virtually all man-made. It now often settles in groundwater, contaminating potable water in agricultural communities around the world.
The excess use of phosphate fertilizers has resulted in excess nutrient run-offs that pollute the watershed and ultimately accumulate at river mouths in concentrations that disturb water quality and habitability. These areas are referred to as “Dead Zones” as the nutrients feed algae. Algae then blocks sunlight from the ocean and consume most of the available oxygen. Dead zones impact those fish and crustacean-rich areas that feed much of the world with protein-rich harvests. The largest of these dead zones is at the mouth of the Mississippi River that drains vast agricultural regions of the center of North America. The Gulf of Mexico dead zone is massive, about the size of Rhode Island, and has destroyed much of the fishing industry in the region. So we know a little about how the soil supports crops and we are learning more; with modern analytics, we are learning much faster. This is very good and it is beginning to help us realize that certain aspects of plant science had been overlooked. It is now time for a correction; “Better living through Chemistry” has worked for a century and now it is time to consider a more natural approach towards crop production, like “Better living through Biology.”
Unleashing the Power of Microbes through Technology
It was actually the first use of microbes, mostly yeasts and fungi that changed the destiny of mankind from being small tribes of hunters and gatherers that lived in caves and practiced spear-throwing, to a society of agrarian communities that realized they could grow crops and then process them to become the major components of their diet. Societies learned how to care for grains, other cereals, vines, and fruit trees through to maturity, then harvest and store what they reaped. It was also discover that yeasts could turn unpalatable grains into tasty breads and of course, beer. This meant that less time need be devoted to hunting down ungulates and lagomorphs and more time was available to drink beer and play darts and poker. And of course the women were the best candidates for planting, tilling, and harvesting crops as well as milling, baking, and serving the food. Yeasts were not only used in breads and beer, but in making cheeses, wines, and preserving cabbage and other vegetables through pickling (vinegar is produced from fruits by certain yeasts). Most of these processes were taken for granted by early society and little if any scientific connection was made. That didn’t happen until the middle of the nineteenth century by, well you probably guessed, another brilliant German scientist, Dr. A. B. Frank. Unlike Drs. Von Liebig, Hamer, and Bosch, who were all chemists, Dr. Frank was a botanist and biologist of great renown. He was so famous that when Kaiser Wilhelm I of Prussia decided that he needed a better source than the French for his truffles that were slathered on his Jagerschnitzel, he turned to Dr. Frank and told him to go forth and bring back tasty truffles.
Dr. Frank, with a team of students all provided with good digging spades, made of good. German steel travelled the countryside from Mecklenburg to Wurttemberg, from Munchen to Munster, but did not a truffle he find. He did however make some amazing observations about a complex community of microbes that lived in the soil around and throughout the root systems of plants. He concluded that this ecosystem was dominated by one particular organism, yet encompassed and supported a plethora of other microbes, mostly bacteria and fungi. In fact, the soil itself was teeming with life. He named this phenomena “mycorrhiza,” or an environment dominated by a fungus or mushroom (myco from the Greek word for mushroom) and its strong affiliation with the roots of plants (rhiza from the Latin word for root). Hence, no truffles for the Kaiser, but Dr. Frank has gone down in history as the “Discoverer of Mycorrhiza.”
Understanding soil biology is quickly becoming the “next frontier” for science exploration. Much has been learned through field trials about the undeniable capabilities of mycorrhizae. These trials demonstrate the positive correlation between mycorrhizae and increased plant growth and vitality using a visual representation. Seeing is believing, even if we do not comprehend the intricacies of the system behind the magic. After all, it is not always necessary to know why something works, but the key factor is that it works (although it is pretty fascinating stuff if you really want to dig, no pun intended, deeper into the biology of it all).
Proximal Soil Sensing (PSS) is an evolving branch of soil science that seeks to provide precise, quantitative, fine-resolution data as an effective and inexpensive method to better understand variability in soil. Scientists are optimistic that the information we obtain through PSS will provide us with sustainable solutions to global issues that we face: food, water, energy security, and climate change.
The Biological Community of Beneficial Biologicals
The population of microbes that dwell in soils can be likened to a social media community like, say for instance, Facebook. You have your “friends.” You “un-friend” people or they “un-friend” you for one reason or another. You may even get booted by the network itself if you commit an atrocious enough transgression. “Invites” are sent out to be a part of a certain group or attend a specific event. You may be “following” certain people without actually interacting with them or “poking” people just to say hello.
Similarly, microbes in soil within and between species form relationships with one another as well as with the plants in attendance at the botanical party; some microbes are friendly toward one another, providing support and bringing out the best in each other while others share a mutual dislike for one another and may even inhibit one another’s success. Still other microbes tolerate one another without getting in each other’s way and just act as passers-by minding their own business.
With the ultimate goal of producing happy, healthy plants, microbes in the soil need to be happy. For microbes to be happy, not unlike employees of a company, they need to be provided an environment of support and encouragement where all of the players can just get along! In doing so microbes can act together as a well-oiled machine working at optimal production. In fact, soil organisms are great indicators of soil quality due to their sensitivity to their environmental conditions.
We are often trained to believe that bacteria is a bad thing that threatens our health. On the contrary, there are beneficial bacteria that are crucial to the development of healthy plants. These organisms may be tiny, but their impact is significant. Through their own metabolism, various species of bacteria are able to free up critical nutrients including nitrogen and phosphorus that would otherwise be unavailable in a usable form for plants to access. In tandem with bacteria are fungi. Like bacteria, fungi tend to get a bad reputation. Quite the reverse, certain fungi actually benefit plants through the establishment of a symbiotic association in which plants and fungi are able to swap nutrients.
Mycorrhizal Fungi: This Tiny Microbe Is the 800 lb. Gorilla
Ahhh, the fungus among us….
Mycorrhizal spores and hyphae are typically microscopic and invisible by the naked eye, however, if unwound and stretched out, a single cubic centimeter of hyphae may exceed the length of a football field! It is through this elaborate network that mycorrhizal fungi are collectively able to tap into resources beyond a plant’s root system and transfer these products back to the roots.
Although these organisms are miniscule, the benefits imparted on their host plants are enormous. The presence of mycorrhizae may be credited for increased nutrient supply; drought tolerance; protection from pathogens; improved soil structure and carbon storage; stronger immune systems to fight off pests and diseases; increased uptake and retention of moisture and nutrients resulting in greater growth thus reducing and/or eliminating water and fertilizer requirements; increased elemental nutrient supply (particularly nitrogen, phosphorus, and potassium), which give rise to primary metabolites (lipids, carbohydrates, amino acids), which give rise to secondary metabolites (vitamins, minerals, terpenes, etc.); increased temperature tolerance. That is quite an impressive list of accomplishments for such a tiny organism!
Plant Growth-Promoting Rhizobacteria (PGPRs): The “A” Team
If you think mycorrhizal fungal spores are small, let’s turn our microscope to 100 times magnification to see our next players. As the title eludes to, PGPRs are microscopic unicellular bacteria that colonize roots and stimulate plant growth. These are nitrogen-fixing bacteria that convert soil-bound elemental nutrients into a form that plants can use. Consider them the key-holder to your bank safe. When you need to pull money out of your safe, you have to call upon a banker to unlock it for you. Similarly when a plant is in need of nutrients like nitrogen, phosphorous and potassium that is fixed in soil and bedrock, it relies on the metabolic pathways of rhizobacteria to free-up these ions and convert them into a currency that the plant can accept.
Bacterial species belonging to the Azotobacter and Azospirillum genera are widely used in agricultural trials. Several strains have gained importance; along with their nitrogen-fixing ability they also enhance plant growth by producing phytohormones, chemicals that regulate growth. Application of Azotobacter chroococcum and Azospirillum brasilense inoculants in agriculture, especially in cereals, has resulted in notable increases in crop yields.
The Bad Players
Throughout all stages of life, from germination to maturity, plants are faced with many obstacles. Such adversities include insect infestation and other pests, disease, contaminants, inclement weather, drought, competition with invasive species, and the effects of agrarian practices. Plants have developed clever means to combat these trials, contributing to the overall resilience of their respective species’.
The Sheriffs of the Soil
Mycorrhizal fungi and beneficial bacteria are the “gatekeepers,” protecting roots from some disease-causing harmful invaders while benefiting from living in the shadow of the root as it exudes sugars into their world as their food source. Further development of mycorrhizae opens these gates and extends the path and area of soil for plant roots to access moisture and nutrients from an expanded pool.
Chemical and hormonal signals give the green light for the initiation of the courtship between roots and mycorrhizal fungi. Once mycorrhizae form, the nutrient and carbohydrate exchange make both organisms stronger and the symbiotic attraction stronger as well. This win-win interaction results in a healthier, more robust plant. During the development of nitrogen-fixing nodules on plant roots, rhizobacteria produce chemicals from the same family as those produced by mycorrhizal fungi. Though two very different signaling processes, mycorrhizal fungi and PGPRs are able to induce similar growth responses by the plant.
Keeping Peace and Prosperity in the Plant Community
“Ecosystem management isn’t rocket science, it’s a lot more complex.”
So now that we know the various hats worn (and sometimes shared) by mycorrhizae and beneficial bacteria, and the contributions they offer to soil and plants, how do we keep them in our good graces?
In an ideal world, we would let it be; the soil and plants would maintain their own harmony like a well-oiled machine and respond intrinsically to change as needed without human intervention. Realistically, we are dependent on farming to sustain the human population and livestock, so we are obligated to interfere to a degree. Keeping in mind that no living being, large or small, exists in a vacuum, we can concentrate our efforts on practicing a sort of harm-reduction style of agriculture and land management in order to conserve and protect soil ecosystems for current and future use. This requires understanding the role of soil organisms and taking advantage of what they offer, restoring soil biology as needed, understanding how agricultural practices affect the soil, amending these practices to best suit both human and nature, and overall, being proactive ambassadors for the soil on which we rely.
Healthy Soils = Healthy Plants
“Soil is an almost magical substance, a living system that transforms the materials it encounters.”
“You are what you eat,” so they say. Likewise, plants “are what they eat (or what they are fed in this case). Though plants lack opposable thumbs to pick and choose what goes into their herbaceous bodies, they do possess complex metabolic pathways that enable them to obtain proper nutrition…given that adequate nutrition is available for their disposal. In some ways we can consider soil microbes the opposable thumbs plants utilize to obtain life-sustaining nutrition. Just as higher order animals rely on the successful production by plants for sustenance and the clarity of mind to make wise dietary choices, plants rely on the complex biological machinery within the soil to mobilize nutrients for them to exploit in order to grow and mature in optimal health.
Just as we study ocean ecosystems and the role each organism plays in the food chain, from microscopic plankton to behemoth whales, we can find equally complex ecosystems and diverse arrays of life within the “sea” of soil, from bacteria to fully mature California redwood trees. The more we learn about the delicate balance that sustains our soil, the better equipped we will be to stay proactive in sustaining the land on which we rely. Like mycorrhizae, we have the power to uphold a symbiosis with Mother Earth that will sustain us if we only remain conscious and mindful of its humble yet invaluable offerings.