Organic Cultivation Starts With Soil

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Why putting media first will be your first real step toward sustainability in a sun-grown operation.

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Thirty years ago, Kerrie joined with other local Colorado farmers to found the wildly popular Boulder County Farmer’s market. Sustainability, Slow Food, community and, of course, organic growing were the passion and dinner topics of the day. Today, these same ideas are just as good as they were back then: Organic growing is again a topic of great passion and energy.

Today, however, in other ways, we are a world away from those days, and the plans people discussed over beers about making the world sustainable and organic have materialized. Organic is a lifestyle, and Certified Organic is a major marketing lever in the food marketplace. But on the cannabis side, growers have been forced into many unsustainable practices due to regulations stipulating where and how cannabis can be grown.

The organic lever is one a lot of cannabis growers want to pull, but can’t become Certified Organic because the U.S. Department of Agriculture (which oversees organic certification in the United States), as a department of the federal government, currently says no to cannabis and organic certification.

We’ll eventually find a standard term to use to market our organically grown products. But, while some people worry about what it’s called, other folks who can farm outdoors have not only the opportunity, but the ability to make organically grown cannabis the standard in low-cost production, and all they need is land, and water, and to pay attention to the organic equation.

The Organic Equation

OM (organic matter) + Soil-Borne Decomposition Agents + Time = Plant Available Nutrients

Organic matter: It all starts with the nutrient sources. Every living thing is made up of elements, and we can extract those elements from dead material. Seaweed is loaded with nitrogen. Bat guano delivers nitrogen, phosphorus and potassium at significant levels, and feather meal is another nitrogen source. The list of organic nutrient sources is relatively small, and indeed, an almost-standard organic mix recipe has emerged that is repeated in almost every article we read. But every one of these sources require harvesting, processing, packaging, transportation and advertising just like any other product. And when we are talking acres of land, it is difficult for those products to compete in cost against good, old plant material and manure that is readily available “just over the fence.” The choice of OM will no doubt be based on cost, so cultivators need to look carefully at their options.

It is a good idea for growers to familiarize themselves with the nutrient character of their source materials.

In an effort to learn more about our own source material, for example, we put earthworm castings in a cup and added enough water to just cover the castings. After 15 minutes, we used an electrical conductivity (EC) meter to test the slurry we just made, and we have seen EC levels as high as 13—a stratospheric level of available nutrients. No breakdown required here; the nutrients are already plant-available.

Decomposition: The natural biota of soil has bacteria, fungi and earthworms that act on OM and reduce it to our plant-available nutrients. Acids and enzymes in the soil also play a role here. These natural decomposing agents are not generally found at industrial strength in the soil, meaning the necessary organic-to-inorganic breakdown process takes time. Field soil amendment is done well ahead of when the nutrients need to be plant-available for the crop. Typical mineralization rates for nitrogen are slow.

One study conducted in 2002 by Brazilian researchers at the Federal University of Rio Grande do Sul—titled “Empirical Models to Predict Soil Nitrogen Mineralization”—showed nitrogen mineralization rates where eight weeks and more of appropriate temperatures are required. No one is going to be growing football-sized colas in eight weeks at that rate.

Time: The last element of our nutrient equation is time, which comes into play on the front end of each season. Armed with the knowledge of how fast nutrients are made available from amendments, growers decide how much lead time they need, and then set an amendment date.

There is no escaping the fact that plants grow based on the nutrients available to them, so if nutrient levels are lower, more time in the ground can make up for the slower growth rate. (That brings the weatherman into the picture, as weather may have more to say about when you harvest than you do.)

Growers can make the most of their time by inoculating plants with mycorrhizae. These fungal organisms colonize plant roots, and being fungi, they create a fine network of hyphae throughout the soil to collect nutrients. As a result, the mycorrhizae are able to significantly enhance nutrient uptake. Mycorrhizae have been shown to provide dramatic results in side-by-side field tests, making them a strong candidate for addition to the field growers’ tool kit. When we can’t feed plants with concentrated nutrients, use of mycorrhizae becomes a highly valuable tool.

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Get Under Your Soil

Understanding the dynamics of soil biota is critical to optimizing results when using organic methods. We recommend growers engage soil scientists to help them develop amendment strategies tuned to their location and soil. For example, studies have shown that incorporating clover rather than manure has resulted in a more robust biota that drove nitrogen mineralization rates as much as five times as when cow manure was used as the amendment, according to “Applied Soil Ecology,” a textbook co-authored by international agricultural researchers and published by Elsevier in May 2016. We will only learn by bringing in the pros.

Microbiological labs can be a great tool for helping growers understand how well the breakdown process of OM will proceed in their soil, as can nitrogen monitoring through each season to help predict yields. They can catalog and count bacteria, fungi and nematodes in soil to provide a characterization in the breakdown capability.

Field farmers perform soil-nutrient analysis every year to determine the nutrient value plants have depleted from the soil and to estimate how they need to adjust the soil’s nutrient content before the next crop.

Likewise, anyone can see just how well an organic system delivers nutrients. Fill a container with the intended organic-media field soil or grower’s mixture, along with all the amendments used to aid and abet the breakdown processes. Don’t plant the container, but do add water to the media, just as if there were a plant there, and measure the media’s EC on a daily basis. Keep the media moist—not drenched, not dry. Get a “direct-measure” EC meter that works in media, indicating the overall nutrient level. Direct-measurement meters eliminate time-sucking “run off”/leachate testing. Measure midway to the bottom of the container.

If the decomposition processes in the media are working, measured nutrient levels will increase. If the EC levels off, nutrients are no longer being released. EC should never decrease since there is no plant to take nutrients out of the media. If the test were run long enough, the difference between the initial and final EC represents all the nutrients that were released by that media over the test time.

Debate vs. Research

One last issue remains to address. The point people make most about organic growing is not about growing, but flavor and aroma. Living soil is held by many to be the source of enhanced flavor and aroma via the chemical byproducts of the bacterial and fungal breakdown activity. For that theory to be proven, someone must demonstrate the fate of the decomposition byproducts—where they go in the plant, how they are affected and what they ultimately become. Are they being taken up by the plant and processed into terpenes, or are those by-products ending up in the plant material as some different chemical that changes flavors? Research must establish a link between the presence of byproducts of decomposition in the root zone and unique flavor compounds in the plant.

The plant’s genetics contain all the code required to produce terpenes from the available nutrients. If the plant converted bacterial waste products into something else, it would have likely been observed in plants and reported by now. We just need to keep working to improve our understanding of organic growing and how it affects the plant character.

Planted in native soil, container, media and nutrient costs all shrink. The plants may not perform like indoor plants, but the cultivation costs per pound of production will be the lowest around, and that rings the sustainability bell in more ways than one.

Kerrie and Kurt Badertscher are co-owners of Otoké Horticulture, LLC and authors of “Cannabis for Capitalists.” They have worked with large-scale cannabis producers for more than six years. Kerrie has been involved with plants her entire lifetime and earned certification as a Professional Horticulturist by the 100-year-old American Society for Horticulture Sciences. Kurt brings his 34 years of corporate experience and operations management skills to bear on the business challenges of cannabis cultivation.