Last week we constructed low tunnels over our day-neutral strawberry plants at UNH's Woodman Farm. Thankfully, we learned a few lessons last year that were helpful to us this year, most notably:
1 - Tie the ends of the low tunnel plastic low to the ground. Last year we thought it would be easier to weed under the ends of the tunnels if the plastic was tied a bit above ground, especially where we had unmulched beds. However, when we went to lower the plastic at the end of the season there were gaps between the ground and plastic at the ends of the tunnels. To prevent this from happening again, this year we tied the plastic as low to the ground as possible, so that when the sides are lowered there are not gaps between the ground and plastic covering.
2 - Plastic stretches (a lot) and we needed a way to easily tighten it. We learned this the hard way last year when plastic on all 60 low tunnels stretched and a pond of water was on top of each just days after installation (pictured right). To tighten plastic last year, we used industrial size cable ties at the end of each tunnel, but they became brittle by fall, and occasionally snapped. This year we purchased a small ratchet for each tunnel. Ratchets were attached to the grounding stake (either a tomato stake or a steel pipe) with zip ties. Then, a piece of strong paracord was run through it, and attached to the plastic using a zip tie (see below pictures). This will allow us to continue removing slack from the plastic as it stretches throughout the season simply by tightening the ratchet.
Because one of the primary objectives of our study is to evaluate plastics for low tunnels, we have many tunnels and they are short, so one ratchet seems sufficient. The longer tunnels we installed over our day neutral variety trial (about 60') covered with 1.5mil plastic required two ratchets, one on each side.
3 - Rolling under plastic sides: We found that with the 6mil plastics it worked best to roll the sides of the tunnel under, up to about the eave of the hoop (pictured right), instead of scrunching up the plastic. This method helps to encourage water runs off the tunnel and does not get caught up in plastic.
However, when using 1.5mil plastic, because it is possible to tighten the plastic a bit more, it is more difficult to roll the sides. For these tunnels, we have been simply scrunching the plastic up to below the eave.
What we've learned already this year...
A few days after installing the tunnels, we still had a few tweaks to make, namely tightening the bungee elastics so they were VERY tight. This is recommended by the manufacturer (Dubois Agrinovations) and also helps to prevent water from pooling. This does not have to be done after installation, but because we did not tie them tight enough the previous week when they were installed, we needed to go back through.
In addition, we found the longer tunnels (60') needed grounding stakes on both sides of every hoop. We are in a relatively windy location, but it appears that the longer the tunnel, the more secure it needs to be. Ways to secure the tunnel include additional grounding stakes, very tight bungee hoops, lowering one side of the plastic (the side of the prevailing wind), and being sure plastic is installed very tightly (another benefit to having a ratchet or sorts on the end).
UP NEXT AT UNH...
We are in the process of removing the first flush of flower trusses from plants so they put their energy into root and vegetative growth. We have removed trusses once, but will go through again this week, and possibly again in about a week or so.
This week we will also be collecting data on plant vigor for all our cover/mulch treatments, and also from the six day neutral varieties included in out variety trial!
Visit the Sideman Lab website to learn about the other neat projects we are working on!
This project is funded by the New Hampshire Agricultural Experiment Station and Tunnel Berries, a USDA National Institute of Food and Agriculture Specialty Crops Research Initiative grant titled "Optimizing Protected Culture for Berry Crops" in collaboration with the following universities: