Knowledgebase
Effects of Prolonged Weed Block Fabric on Soil/Microorganisms #781742
Asked February 12, 2022, 6:59 AM EST
Hello, amazingly wise extension people!
I have a soil question for you that requires some background. Last summer, I solarized our entire front and back yard area, with very good success. I used 2 mil clear plastic, and kept the area covered for 8 weeks during July/August. I took the soil temperature at about 6" depth on clear days during peak heat cycles, and the temperature was regularly around 110 degrees. I removed the plastic and found that the overwhelming majority of weeds had been killed. Very happy with the result!
As we headed into autumn, and not having the availability or resources to begin any landscaping of the area, I decided it best to cover the yard areas with black weed fabric for the autumn/winter months in the hope of preventing any lingering weed seeds from germinating. This is the weed block fabric that I used: https://www.amazon.com/gp/product/B06VV1K4ZC/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&th=1. It is supposed to effectively block weeds, while allowing air and water to penetrate and keep the soil nourished. The yard area currently remains covered with the weed fabric. My plan was to revisit the landscaping of the yard in early spring of this year, at a more appropriate time/season.
Well, we have had a personal/medical emergency arise that is going to delay any landscaping this spring or summer. Which leads to my question. Given that I will not be able to complete any landscaping until autumn 2022 at the earliest and very likely spring of 2023, my plan is to leave the weed block fabric on the yard area until I can landscape -- so as to continue to suppress weed growth and not disturb the soil. What would you expect the effects of this prolonged covering will be on the soil and soil microorganisms? Will it be harmful to the soil? Is it better to remove the weed block fabric, expose the soil, allow new/dormant weed seeds to germinate [and just deal with them], and potentially undo the benefits that the solarization brought? Or should I keep the fabric in place for this additional extended time?
I would really appreciate your guidance, and the costs/benefits of both leaving the fabric in place and removing it. Thank you very much for giving it your time and thought!
Alison K.
Adams County Colorado
Expert Response
Hey Alison,
The fabric is not great for soil health but I don't necessarily think that should stop you from leaving it on for another season.
A healthy soil ecology needs moisture, oxygen and food (carbon containing stuff- i.e. organic matter). Even "breathable" landscape fabric interferes to some extent with the first two. In terms of organic matter, there is probably a decent supply from the weeds/lawn you killed.
All that said, I think you are fine to leave it covered. Not much is going to change in another growing season. You might consider getting a soil test before you start the project to see what your soil organic matter content is. You will probably want to consider adding an organic amendment before you plant anything. We can help you interpret a soil test to figure out how much you might need to add when you get to that point. More information on soil testing can be found here: http://csuhort.blogspot.com/2014/02/soil-testing-its-good-thing_24.html
Hope this helps, please let me know if you have further questions.
Thanks,
Eric
Hey, Eric!
Thanks very much for your answer and additional information/explanation. It's a relief to read.
Here's a bit more background on the yard area and soil. We bought the property early last year, and both the front and back yard areas had not been landscaped at all. There was no lawn or garden -- only a variety of weeds, including bindweed, and two trees on the property border. There currently is no irrigation system. I did a soil test early last year, which was processed by CSU. A copy of the soil test is attached, with the caveat that the nitrogen value is missing because CSU's nitrogen testing apparatus was broken. The values actually are good for micronutrients, pH and salts. And the organic matter -- 3.5% -- really isn't all that bad for soil that had been pretty badly neglected.
Prior to covering the yard areas for solarization, I amended with corn gluten meal [9-0-0 NPK] both as a nitrogen supplement, and to assist with the killing of any new weed material that managed to sprout. So, I'm hopeful that that amendment served its purpose of both boosting soil nutrient levels, and managing any new weed growth post-emergence.
My plan once I remove the weed block fabric next year is to lay down 1" or so of Biocomp compost from A1 Organics. I then plan to plant a drought-resistant grass in some areas, but focus on putting in xeriscape plants and some decorative rock/mulch so as to minimize water use. I also already have built/installed multiple raised garden beds [with Planters Mix soil from Pioneer Sand, locally] in a large area where I did remove the landscape fabric earlier this fall, and which will be ready for planting this year.
With that additional information, does my plan still look okay to you?
Thanks for the additional review and comments!
Alison
Hello again, Eric!
Did you receive my follow-up response dated Feb. 17, 2022? Just checking to make sure the question/issue was re-opened. If you didn't receive it, please let me know and I'll re-send. Thank you!
Alison K.
