Using Silage Tarps to Kill Weeds
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January 29, 2024
On our 1-acre flower farm where we use mindful, regenerative agriculture methods for growing beautiful cut flowers and cut foliage, Silage Tarps are a tool we rely on for no-till weed control. I have some thoughts about using silage tarps on the farm, both good and bad, and in this post I’ve described timelines for how to use silage tarps to kill weeds on the farm. I hope that our experiences in silage tarping as a form of organic weed control will help you decide whether it’s right for your needs.
I also wrote a post on How to Hold Silage Tarps Down that you’ll also want to read before getting into silage tarping.
What are silage tarps?
Silage Tarps are large, impermeable plastic sheets that are traditionally used to cover harvested crops such as hay, silage, or grain. Silage tarps play a crucial role in the process of fermenting and preserving crops by creating an airtight seal that effectively blocks out oxygen and prevents spoilage. The tarps help to minimize the risk of mold and rot by keeping rain out, ensuring that the stored crops remain in good condition.
We use Silage Tarps not to preserve harvested crops, but to kill weeds and open up new areas for planting.
Related: Why is Tilling So Bad?
where to buy silage tarps
You can find Silage Tarps for sale at really good prices on Amazon. I have two 50’x100’ Silage Tarps, which in all honesty, were super expensive and very hard to move around. Tarps of that size are incredibly heavy, especially when rain collects on top of the tarps during the season. We ended up cutting both of those extra-large tarps in half. I recommend starting with these 20’x100’ Silage Tarps which are a good size for 2 people to move around.
If you have a smaller backyard garden, this 20’x24’ Silage Tarp is a great size. I use this one in my home backyard to kill weeds in the Spring before planting my veggie garden. If the tarp is still too big for your space, you can simply fold it onto itself.
Here are two High-quality 6 mil Silage Tarps for sale on Amazon that I have used and recommend:
silage tarps for weed control
In organic farming, we use silage tarps on the ground to cover and suffocate grass, weeds, and other undesirable plants in order to open up new growing space. Silage tarps are made of completely impermeable plastic and are black on top, so unlike landscape fabric or a traditional tarp, no water or sunlight gets through the silage tarp at all. When left directly on the ground for a period of time, everything underneath the silage tarp will begin to suffocate and die, allowing the farmer to work the ground without tilling it up. We avoid tilling our soil repeatedly because tillage destroys soil structure and causes compaction.
Silage tarps are a wonderful no-till tool for weed management on the farm, when used correctly. I have seen farmers post on Instagram about using silage tarps in ways that have made me scratch my head. Some farmers have posted “tutorials” of themselves throwing down a silage tarp, then tilling up the soil, then planting. To me this is backwards, and I’ll explain why.
how to use silage tarps for weed control
The whole point of using a Silage Tarp is to kill everything underneath it and create a stale seed bed. The goal of silage tarping is to kill weeds with the least amount of effort, and reducing the need to till the soil. I would consider silage tarping a lean farming practice and one that has saved our crew tons of time in managing weeds during the growing season.
There are, however, right and wrong ways to use silage tarps. You definitely do not want to till your soil after laying down the silage tarp. The whole point of the silage tarp, again, is to kill the weeds underneath it. If you pull the tarp up and immediately till the soil, you expose all the dormant weed seeds, eventually causing an explosion of weed growth, and your silage tarping will have been a worthless endeavor. If you think you need to till the area before planting, till BEFORE laying your tarp down.
Related: Using Burlap & Leaf Mulch as Organic Weed Suppression
Here is an example timeline of how we would use a Silage Tarp for different times of the year.
Using a Silage Tarp to open up a brand new planting area for Spring/cold months
Mow area so there is no tall brush (leave clippings)
Lay silage tarp on the ground; hold down with sandbags or concrete blocks — read our method on holding tarps down using concrete blocks
Let silage tarp sit for 6-8 weeks
Remove silage tarp; Move to a new area (easiest choice) or fold up and store if necessary
Pull invasive/perennial weeds that were not killed by silage tarp
Mark out beds and lay compost/prep soil as you normally would. Broadforking the beds is highly recommended.
Plant!
Using a Silage Tarp to get a large area of weeds under control during the Summer/warm months
Mow area so there is no tall brush (leave clippings)
Lay silage tarp on the ground; hold down with sandbags or concrete blocks — read our method on holding tarps down using concrete blocks
Let silage tarp sit for 4 weeks in hot months
Remove silage tarp; Move to a new area (easiest choice) or fold up and store if necessary
Pull invasive/perennial weeds that were not killed by silage tarp
Prep beds if you intend to plant here (again, Broadforking is highly recommended), OR seed cover crops — you can use the Silage Tarp on that spot again to terminate the cover crop when it’s reached the correct stage of growth
do silage tarps kill all weeds?
The short answer is no. Silage Tarps do an amazing job suffocating annual plants, but deeply-rooted, invasive weeds will not die under a silage tarp, even if left for an entire year — I know from experience. These plants include, but are not limited to: Dogbane, Bindweed, Bull Thistle, Canada Thistle, Mugwort, Dock, and I’m sure many others that are not on my property but could be on yours.
In this case, when we have leftover perennial weeds after silage tarping, we dig them out. Once they’re gone, they’re gone. It takes a lot of work, but if you are prepping a fresh seed bed or planting bed, the extra effort spent digging out perennial weeds will be worth it in the long run, if you are intending to establish no-till perennial raised beds like we have on our farm.
is there a downside to using silage tarps?
The short answer is actually yes, there are a few downsides to using silage tarps.
Silage tarps have caused noticeable soil compaction on my farm in some areas. In other areas, I have not noticed significant compaction. I think it comes down to how compacted the soil is before the tarp goes down. If water tends to stand in a particular area (a sign the soil is compacted) and you throw a silage tarp on it for awhile, that area will end up more compacted than before. On my farm, non-compacted areas seem to be fine after silage tarping. This is just my very non-scientific experience and observations with my eyes and hands — which is incredibly useful, by the way, so take lots of pictures and notes when you’re out doing this in your own field.
Related: How to Plant Living Clover Pathways
The other potential problems with silage tarps are that silage tarps could leach chemicals into the soil (they are plastic, after all), and they could cause harm to soil microbial life if left out for too long during hot months of the year.
As of now, I don’t think there is enough documented evidence to say whether or not silage tarps leach harmful chemicals into the soil, but it seems like an obvious inference that they could. As for whether or not silage tarps cause harm to soil life, it also seems obvious that, if a tarp is left on a spot of soil for too long, the soil will become hot quickly and potentially fry and dehydrate soil life underneath it.
To prevent silage tarps from killing soil life, we always make sure there is some sort of cover crop growing on the soil before using the tarp. If there is a cover crop (even if it’s grass/lawn or weeds), then soil microbes and other creatures have organic matter to digest. The plant residue will also help keep moisture in the soil, even underneath the tarp. Additionally, I’d suggest tarping on a schedule so you’re only leaving the tarp on for a few weeks max during hot Summer months.
other ways to use silage tarps on the farm
There are other things that silage tarps are useful for, beyond killing weeds and opening up new planting beds.
Use a silage tarp to cover your compost pile - rain and snow will leach nutrients out of your pile over time, so keeping it covered over winter and in cold months will preserve those nutrients longer.
Use a silage tarp to cover your exposed equipment - protect your tractor implements, wheelbarrows, and other farm tools from the elements over the winter season.
Use a silage tarp to suffocate tough, invasive perennial weeds over a long period of time (we are currently doing this with a section of bindweed on our farm).
alternatives to silage tarps
Silage tarp alternatives might include the following:
Landscape Fabric - this woven plastic fabric does allow air and water through, so it won’t do as quick of a job killing what’s underneath, but it does do a fine job terminating annual plants when left for 4+ weeks. Click here to read about the Pros and Cons of Using Landscape Fabric.
Covering garden beds with Builders’ Paper & Compost - covering your garden beds with 1-2 layers of builders’ paper, then covering the paper with 3 inches of compost, will help keep annual weeds under control. You can plant directly into this with a dibber planting tool, which is a handy tool for punching neat holes into the soil for planting and will punch right through the paper.
Sheet Mulching with Cardboard - if you have a season to wait to open up new beds, you could sheet mulch the space with cardboard and compost or top soil. Click here for our Sheet Mulching Tutorial.
In conclusion, I have mostly enjoyed using silage tarps on my farm. Silage tarping has cut down on weed management big time, which is our biggest time suck on our herbicide-free, organic flower farm. The thing I will be more diligent about is using silage tarps on already compacted areas because we don’t want those areas to become even more compacted after tarping.
Read our methodology on holding tarps down using concrete blocks.
I hope these thoughts on my experiences using Silage Tarps on my flower farm have helped you decide whether or not it’s the right move for you. If you are a no- or low-till farm with organic weed control methods, I definitely recommend adding silage tarps to your regimen!
peace, love, and tarps for all,
Fran Parrish
