Published: March 21, 2017
This is the 2016 Minibeds-on-Plastic experimental garden.
This essay explores the similarities and differences between my Minibeds-on-Plastic gardening system and Paul Gautschi’s Back To Eden system, first introduced in Part 1 and 2 of this series.
Both methods prioritize soil covering, or mulching. However, Back To Eden is recognized for advocating wood chips as soil cover, although Paul Gautschi has recently stated that any material, even rocks, can be used. On the other hand, the Minibeds-on-Plastic system utilizes a large, single sheet of thick black plastic.
The primary function of mulch is to safeguard the soil against drying out, compaction, and weeds while fostering biological activity. Mulch is essential for both Back To Eden and Minibeds-on-Plastic gardening, both of which promote a no-till approach.
Many gardeners consider weed control the most significant advantage of mulching, particularly those with prior gardening experience.
Weeds compete with garden plants for essential resources, such as soil moisture, nutrients, root space, and sunlight. Vegetables generally struggle to outcompete weeds.
In my experience, natural mulches like wood chips effectively suppress many weeds, but not all. Black plastic mulch, however, effectively eliminates all weeds in the covered area, a highly desirable characteristic.
In Teaming With Microbes, Jeff Lowenfels acknowledges the effectiveness of black plastic sheeting as mulch, yet he subsequently disregards it and focuses on natural mulches. This bias towards natural mulches is common among organic and natural gardening enthusiasts, including myself for over 30 years.
However, many organic market gardeners and small farmers recognize the substantial benefits of black plastic mulch and have been using it successfully for decades.
Although some organic food producers may have reservations about black plastic, they acknowledge its effectiveness and prioritize production and success. Weed-free gardening significantly contributes to a successful harvest.
Even the Rodale Institute, a pioneer of the American organic movement, recognizes black plastic mulch’s effectiveness in its 2014 report, Beyond Black Plastic.
“Black plastic is highly effective in preventing plant growth in the areas it covers. In comparison to growing vegetables in bare soil, using black plastic considerably minimizes the requirement for other weed control methods, such as herbicide application, cultivation, or labor-intensive manual weeding. Black plastic also offers the added benefit of warming the soil, which in some cases allows for earlier planting. For these reasons, black plastic has gained popularity over the past 50 years.”
The Rodale report does point out drawbacks of black plastic mulch, such as its inherent unsustainability and challenges with recycling.
However, plastic is widely used, and its use in gardening can be justified based on its benefits. For me, using black plastic sheeting in my garden helps me achieve a level of plant yield, success, and personal satisfaction that I wouldn’t otherwise achieve, given my time constraints and physical abilities.
Furthermore, I’ve made environmentally conscious choices in other areas of my life, like siding my house with wood instead of plastic, avoiding plastic soda bottles, and declining plastic bags for small purchases. These choices, I believe, balance out any perceived drawbacks of using plastic mulch in my garden.
Another concern raised in the Rodale report is potential negative impacts on soil microbes. The report suggests that excessive summer heat trapped under the plastic could harm beneficial fungal activity in the soil, potentially creating an imbalance in favor of bacterial activity. This imbalance might hinder plant growth. Here’s what the Rodale report summary says:
“The average maximum soil temperatures in the black plastic treatments were 5.8 °F higher than the rolled and mowed [organic mulch] treatments in June, 4.0 °F in July, 2.0 °F in September, and 0.5 °F in October. Minimum soil temperatures in 2012 were higher in the black plastic treatment in June and July by roughly 2 °F.”
These temperature variations, while notable, are lower than I anticipated. Whether these differences are significant enough to negatively affect soil biology remains unclear, as the Rodale study didn’t specifically investigate this aspect. The report merely suggests a possibility.
Also, the report doesn’t mention the depth at which soil temperatures were measured. Were these measurements taken at the surface level, one inch deep, or two inches deep? The depth would significantly influence temperature readings. Is the soil biology truly harmed by this heat, or is it merely temporarily affected in certain areas under the mulch?
My past experiences using black plastic mulch suggest that the temperature beneath the plastic might not be a significant issue. However, I plan to test this in my experimental garden this year.
The key takeaway here is that black plastic is a remarkably effective garden mulch. The only major disadvantage, in my opinion, is the lack of aboveground biomass and its associated benefits for the soil. However, my approach to Minibeds-on-Plastic gardening doesn’t neglect biomass and soil biology.
These aspects will be covered in the next and final installment of this series, where I’ll also explain how Minibeds-on-Plastic gardening differs from traditional black plastic gardening by addressing common concerns associated with black plastic use.
to continue reading Part 4 of this series