This week I've received a couple of questions about how we use tarps in our no-till gardens. Good question! I was wondering the same about 4 years ago as I contemplated the concept of no-till gardening. The main problem I could see was that our garden space is quite large- about 2 acres- and weed control would be a big problem without tilling.
First, why no-till?
There are many good reasons to strive for no/low-till gardens. Here are my top three: 1. Preserves soil structure and the microbiology in top soils. 2.Sequesters carbon in soil 3. Prevents soil compaction caused by repeat tilling with machinery.
I clearly saw the benefits of no-till gardening and was curious about how tarps and mulch could be used for weed suppression.
After researching the use of vinyl tarps I bought a large 20x60 ft recycled billboard tarp. If you google "used billboard vinyl" you will find a few websites that sell these. One side has a corny advertisement and the other is black. There are varying thicknesses of vinyl and even the thinner material seems to be durable. Shipping is almost as much as the item itself so just shop around until the price matches your budget. I've also heard of people calling billboard companies and getting them cheaper. We have paid about $50-$80 each depending on size.
The first tarp I purchased about four years ago is still intact. There are a few holes from snagging on sticks. We now have 7 of these tarps. By rotating them through the space we can cover about 1 acre of our garden over 4-5 months. The other acre is divided into two isolation fields that still get tilled once a year in May before we do our summer planting.
So how does it work? This is the method we have come up with.
1. Weedeat your garden space when the plants are done. Alternately clip your plants down to the ground and compost. In a small space pull plants out by the roots and compost. I like mowing it all down because that way the plant material goes back into the soil and I don't have to haul it away!
2. Make sure the ground is moist. You could even run a sprinkle a few days in a row. Working with seasonal rains is great too.
3. Spread the tarp over the ground you wish to clear and weigh it down all around the tarp. Rocks are great, as are cement blocks and metal stakes. It is surprising how strong the wind is, so pinning it down is really important.
4. Wait 4-8 weeks then have a look under the tarps. Amazing things happen! There will be a composting effect on the material that was mown plus any weed seeds that were in the top layer of soil will have germinated and finding no light, died.
5. If the ground is cleared enough for you to plant, move the tarp to the next patch of ground to clear or fold it up and store it out of the sun.
We end up doing this almost year round. Soon, when the ground moistens a bit more and I can tear the squash out, I will start tarping and continue clearing the garden this way through May.
If the soil that is revealed is bare, get some mulch on it ASAP. (My favorite right now is organic rice straw.) One of those amazing things that happens with tarping, especially through the winter and spring, is that the soil becomes light and puffy. The worms come back to the top layer of soil and mine it for food leaving behind their gifts of aeration and fertilization.
The tarp creates a microclimate for soil biology and protects from the compaction caused by winter rains. A good layer of straw or wood chip mulch in the winter will also protect your soils. I highly recommend you do not leave your garden bare over the winter! Cover crop is another option and we will get into that next weekend!
How do you plant into the soil after tarping?
1. Add more mulch if needed.
2. Moisten the tarped ground for several days prior to planting. We irrigate with drip tapes and I run the tapes on top of the mulch. This keeps the mulch from blowing away and I can regularly inspect the lines for critter damage.
3. Plant transplants or seeds through the mulch. Pull back mulch around plants as needed. If you want to direct seed a line of turnips just pull back the mulch and gently hand prep a line using a hoe or similar tool.
I have found that no-till also just means less-till. Sometimes an area needs to be worked with my wheel hoe or even a broad fork if the soil seems compacted. Sometimes we end up working a few beds with the tractor rototiller set at only a few inches for a shallow till. Sometimes life, and mega tall weeds, happen...so instead of perfection we just try for better soil health each year.
Let me know if you have any questions about no-till gardens and how you can get this going in your space.
Have a great weekend!