I haven’t written about the practices on my personal farm yet in this blog, this post will be the first. Now, my business partner Jordan and I are relatively new farmers, so I am not all that confident to share agroecology advice. We frankly have so much to learn. However, this season our use of silage tarp has had noticeable enough of an impact that I felt the need to share what we have discovered.
In this blog post I will be discussing what we learned about the technique, how we used the product, the effects we have seen so far, lessons learned, critical weaknesses, and the state of scientific research on its usage. The main argument of this article is that silage tarp has been really effective for us so far, however we regret the heavy use of plastics, and would like to see more research on silage tarp for the creation of stale seed beds.
First, a bit about our farm. Our operation is called Green’s Creek Farm and we are located in Blackburn Hamlet in the east end of Ottawa. We are farming as a partner enterprise with Just Food Ottawa using an acre of their land at the farmer incubator site. Last year I operated a 10 member, organic community-supported-agriculture (CSA) box programme but quickly discovered that this was too much work for one person at my skill-level. This is when my good friend Jordan agreed to join me in the enterprise. Through our combined interests we have decided to move towards the production of organic medicinal herbs and breeding heirloom vegetable seed, though we are planning on running a veggie CSA again in the 2017 season. But that is enough about us.
This season we decided to use more of the agroecology techniques promoted by Jean-Martin Fortier in order to move towards a no-till system of production. One of the strategies we decided to go with was the use of UV-treated silage tarp for the creation of stale seed beds to reduce weed pressure.
Basically, the way it works is you take a thick piece of black plastic and put it down over your growing space in the spring before weeds pick up. The heat and moisture retention produces ideal conditions for all weed seeds to germinate very quickly. By blocking out the light from the soil all of the germinated weeds then eat though their stored-up energy and eventually die off. What results is a patch of relatively bare soil with a bunch of dead weeds.
The following is the story of our process and results:
Step 1 – Till the Soil
Our goal is to eventually operate with minimal tillage – mostly only through use of our walk-behind BCS tractor. However, in order to start the transition we figure that in order to reduce the weed pressure we need to do some light tillage to start the process. We tried two methods at different times of the spring. For our first attempt, we cut all standing vegetation and put the tarp directly over it. We then did a pass with the tiller on the tractor when the tarp had done its work and it was removed (although a walk-behind tractor would do the trick too, just shallower).
For our second attempt we had already tilled the soil before we put down the tarp. What we saw is that this technique had the best impact on producing a stale seed bed. We are going to be tilling first or even preparing your beds in advance before before tarping from now on.
It is important to note that this section of the field was covered with buckwheat during the 2016 season, which had a noticeable impact on weed pressure.
Step 2 – Cover Section With Silage Tarp
UV-treated silage tarp is a large and thick sheet of plastic that is treated so that no sun gets through and to prevent corrosion from long-term exposure to the sun. It is basically and massive, super-stable piece of plastic that blots out all light over that which it covers.
We shopped around a lot for silage tarp that came in precisely the dimensions that correspond to the standard bed sizes we use on the farm. We work entirely with 50’x5′ beds in sections that are 200′ long (40 beds per section). We were eventually able to find a roll of tarp that was 100′ x 50′ from Ritchie’s Feed and Seed on Innes Road in Gloucester for just under $500. Dubois Agroinnovations also had silage tarp, but they were a bit more expensive and did not have the size we were looking for.
Having the 100 x 50 tarp permits us to prepare beds in rotation as we can build and plant them.
Step 3 – Wait Three Weeks
This is hard to do, especially when you are getting antsy to get transplants into the ground. However, it is well worth the wait. After three weeks we removed the tarp and what we saw was yellow and spindly weeds everywhere just barely hanging on to their lives. There was also a fair amount of still-living, established rhizomatic weeds (quack grass, thistle, etc.) which was still green. However this was manageable to remove through bed raking.
One thing to note is that in early spring when it is still cold out the space under the tarp becomes an incredibly attractive place for voles, snakes, and field mice. When we removed the tarp they were everywhere and rushing to get back to the grass. If this makes you squeamish, keep that in mind. Needless to say, I feel like the local coyotes are now our biggest fans.
Step 4 – Bed Building and Planting
If you are working in a newly broken field like we are you are going to have a lot rhizomes to rake out when you build your raised beds. In addition to using the UV-treated silage tarp we are also using plastic mulch wherever possible (non-biodegradible). I will go more into the use of plastic much bellow, but it is another fantastic way of controlling weed pressure.
Findings
We were able to notice reduced weed pressure at the beginning of this season compared to last season where I had farmed on land immediately adjacent to where we tarped.
It is hard to say for certain whether the tarping is precisely what has resulted in this one case where we noticed reduced weed pressure, especially since the site was under a buckwheat cover crop the year before. It is therefore inconclusive whether silage tarping is having an impact on weed pressure.
Lessons Learned
As mentioned above, we learned that we would till and even form our raised beds before putting down the silage tarp.
Another thing we learned is that it is best to not try and move it during or after any rain. It doesn’t seem like it should be all that heavy, but the amount of water that pools on the tarp is immense! In addition, don’t try to just drag it to the next section of the field you are planning to cover; instead, fold it up and use a wheel barrow to bring it where you need it next (again, very difficult after a rain).
Beyond the tarp itself, we keep reading that using a flame weeder in conjunction with the silage tarp increases the effect of the stale seed bed. We are planning on borrowing one from some friends next year to see for ourselves if it works for us.
Finally, one application we are particularly excited about is bringing it out in the early spring and putting it out on the snow to get the snow melting quicker so that we can get planting earlier.
Critical Weaknesses
I can already anticipate what kind of feedback I will receive for this post: namely, that so much plastic is being used with this method, especially when paired with use of plastic mulch.
I know, and I feel thoroughly guilty about this.
However, our understanding is that our soil building practices should bring down weed pressure over time thus mitigating the need to use plastic mulch. And generally, we will probably just be better farmers by then and have devised a more ecological means of weed pressure control. Biodegradable corn-oil-based plastic mulches do exist, however it has been removed as a permitted material that can be used in certified organic production because of the petroleum-based chemicals it has been found to contain. Besides, I always wondered what the “ghost-acreage” of this was in terms of producing corn plastics. Ghost acreage is the primary concern that I have with using plant-based mulches such as straw.
Our reasoning behind use of the tarp itself I still feel is sound. In terms of prepping stale see beds, this is a very cost-effective means to saves us time on the tiller, which takes a lot of gas. Over the life of the tarp I feel like this will lead to a significant reduction in gas-use, and the no-till strategies we are pursuing should in theory help sequester carbon and prevent the release of other greenhouse gases released through tillage.
What Does the Science Say on the Usage of Silage Tarp?
I did a search in the academic and gray literatures databases to which I have access and I have not found any studies done on the use of this technology. All literature on stale seed bedding that I could find examines use of a flame weeder, basket harrows, and herbicides.
This is to say that it does not appear as if any formal research has taken place studying the effects of silage tarp usage for this application. If there are any graduate students looking for an simple and manageable research project, this is certainly a great topic that is in desperate need of study, and we’d be happy to be a trial site.
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