Date: March 22, 2017
This photo showcases peak production within an 18-inch diameter mini bed placed on plastic. These small beds, mulched with grass clippings, were the predecessors to my concept of 30-inch by 30-inch wood-framed “Minibeds-on-Plastic.”
The previous installment of this series highlighted black plastic as the most effective weed barrier for gardens. Its popularity among numerous gardeners is a testament to this fact. While it is a synthetic material, it effectively mimics the benefits of soil cover without requiring significant amounts of organic matter like wood chips, straw, or hay, which can be challenging to obtain for larger gardens. Black plastic mulch offers a biomimetic approach to this challenge.
However, there are some downsides to using black plastic mulch. Primarily, wind can easily lift and move the plastic unless adequately secured, and common fastening methods can be inconvenient and not entirely effective. This issue is further amplified when using the standard long, narrow strips of black plastic mulch, which are typically four feet wide.
The Minibeds-on-Plastic gardening method effectively eliminates the problem of wind lifting the plastic. This system employs a single sheet of black plastic secured with strategically placed mini bed frames.
For instance, my experimental Minibeds-on-Plastic garden uses a 24-foot by 44-foot sheet of plastic, accommodating 45 mini beds. The edges of this expansive sheet are secured by burying them in a shallow trench, adding weights, or pinning them down. I’ve incorporated all three methods for added security.
The Minibeds-on-Plastic method’s effectiveness in preventing wind lift was clearly demonstrated in my upstate New York experimental garden last month. During an unseasonal February thaw, a strong windstorm hit while my garden was completely bare. This storm lifted and tossed several sheets of sheet metal roofing I use for mulching a walkway, even though they had been in place for years without issue. Additionally, the wind moved several weighted-down plastic sheets I was using as protective covers on some long raised beds.
Remarkably, my experimental Minibeds-on-Plastic garden, located directly adjacent to the sheet metal walkway, remained entirely undisturbed by the strong winds. This real-world test provided compelling evidence of the system’s effectiveness, and I was extremely pleased with the outcome.
Another common issue with black plastic mulch is its thinness and single-season lifespan. Using the typical long strips necessitates removing and disposing of them annually, creating an unwelcome chore.
However, the Minibeds-on-Plastic system allows the large plastic sheet to remain in place for multiple years. While replacement will be necessary eventually, using a thick, UV-resistant plastic can significantly extend its lifespan. I’m currently assessing the durability of the six-millimeter, UV-resistant bunker cover I’m using and anticipate a minimum of three years of service.
Tom Doyle, whose work inspired my Minibeds-on-Plastic garden design, reportedly used a large sheet of specialized black plastic that lasted for decades. There’s potential that the economical, recycled billboard plastic tarps, which seem more durable than the six-millimeter bunker cover, could offer similar longevity. This spring, I’m planning to create a small Minibeds-on-Billboard-Tarp garden to evaluate its effectiveness.
Integrating Biomass with Minibeds-on-Plastic
The only significant drawback I’ve encountered with black plastic mulch is its inability to nourish the soil and its organisms, unlike organic mulches. However, my experimental Minibeds-on-Plastic gardening system incorporates organic mulch for soil health. Each 30-inch by 30-inch mini bed will have a layer of natural mulch.
I plan to use shredded leaves for mulching the mini beds. Additionally, I’ll be utilizing organic material harvested from the mini beds themselves, which brings me to a key aspect of the system I’m developing.
I will plant a variety of cover crops in the beds to cultivate root biomass. Certain cover crops generate significantly more root mass than aboveground biomass. My focus will be on maintaining a consistent and rotating supply of different root biomass within each mini bed.
I recall Elaine Ingam once stating that “extensive aboveground biomass is misplaced biomass.” Her reasoning was that roots, both living and decomposing, are a direct and effective food source for soil organisms, especially in no-till gardening. Importantly, these roots extend beyond the boundaries of each mini bed.
No-Till Minibeds
This brings me to another crucial element of my Minibeds-on-Plastic garden system: no-till gardening. I won’t be digging or turning the soil in the mini beds. While there will be occasional light cultivation and minimal disruption during transplanting, the emphasis will be on minimizing soil disturbance. All plant roots, except for harvested crops, will remain in the soil.
Admittedly, this approach contradicts my decades-long gardening practices. My instinct is to remove spent plants and meticulously prepare the soil bed. However, last year, I resisted this urge in a few raised beds within my garden. Instead of uprooting plants and tilling the soil after harvest, I simply cut the plants at ground level and planted the subsequent crop alongside the remnants. The results were successful.
This particular garden bed had been used for growing spinach. Once the spinach reached the end of its cycle, I cut the plants at ground level and sowed three rows of peas directly into the undisturbed soil. When the peas emerged, I lightly cultivated the bed to manage weeds and applied a mulch of shredded leaves, as seen in the image.
To prepare the bed for garlic, I removed the pea plants but left their roots intact. I extracted a few roots to examine the nitrogen-fixing nodules, and they were plentiful!
This image depicts the planting of garlic in the bed. The only disturbance to the soil was the creation of holes for each garlic clove. If pea roots obstructed the planting area, I removed them. The soil texture in the bed was exceptionally friable. Post-planting, I applied a thick layer of shredded leaf mulch. Currently, this bed is blanketed in snow.
The objective of this no-till method isn’t solely to reduce labor, though it does, but to maintain soil structure and minimize harm to soil organisms. These organisms are essential for providing nutrients to plants, and we must prioritize their preservation and growth. No-till gardening effectively accomplishes this. For a deeper understanding of soil health and the importance of no-till practices, I highly recommend watching the Ray Archuleta series on the subject.
My point is that I will manage the soil beneath and around each mini bed with a focus on soil health. There’s much more to explore on this topic, such as the importance of soil oxygen and how plastic mulch can actually enhance oxygen levels in the soil below.
While this might seem counterintuitive, my Minibeds-on-Plastic report delves into Tom Doyle’s perspective on “oxygen fertilization.” Initially skeptical, I’ve come to realize that there’s merit to his ideas.
Recently, I came across a YouTube presentation by soil health advocate Jerry Brunetti, where he asserted that “oxygen is the paramount fertilizer in soil.” The Minibeds Report also extensively covers Tom Doyle’s experience of never needing to water his plastic-covered garden.
One final point: When cultivating cover crops in the mini beds, the aboveground biomass can be utilized as organic mulch directly within the beds or composted. Alternatively, it can be spread over the black plastic during warmer months to provide a cooling layer.
If a mature cover crop in a mini bed grows excessively dense, hindering the planting of the subsequent crop, or if the top growth needs separating from the roots to halt further growth, I plan to cut the cover crop low and then divide the dense root and stem mat into manageable sections using a knife. I’ll then sever the plants just below the surface and invert the biomass, using it as a mulch layer. The aboveground biomass will never be incorporated into the soil. While this process might be labor-intensive on a larger scale, it becomes far more manageable within a mini bed system.
p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Helvetica; -webkit-text-stroke: #000000} p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Helvetica; -webkit-text-stroke: #000000; min-height: 13.0px} span.s1 {font-kerning: none}
This concludes this essay series. As you’ve seen, Minibeds-on-Plastic presents a comprehensive and manageable gardening system. It allows for focused attention on a diverse array of crops in smaller, manageable plots, promoting high-yield cultivation and maximizing productivity.
My “theory” behind Minibeds-on-Plastic centers on the idea that manageability, efficiency, and productivity lead to the most fulfilling gardening experience. The upcoming 2017 Minibeds-on-Plastic experimental garden will either validate or disprove my system.
Stay tuned.
to revisit Part 1 of this series.