Three Month Update On The Back Yard Solarization Project

Solarization progress

In Mid April I started a Solarization experiment where I use solar heating to kill off everything in the soil of my back yard. So far the results have been mixed.

The weather in Rio Rancho has cycled between days of heat and days of cool with rain. The cool days help to create a greenhouse effect under the plastic that cause plants to grow and the days of heat have killed them off. This is good since it’s easier to kill plants than seeds. Hopefully everything that can sprout has sprouted and died.

Since we haven’t had enough days of heat in a row, I don’t think the ground has really baked deep into the soil. It doesn’t appear it has baked the surface enough to decompose organic matter there.

The cycle of rain and heat appear to be over and we are now we are just getting heat. Parts of dead vegetation with sharp edges along with the prolonged time in the heat has caused some of the plastic to break down and break apart. Of the two sheets I put down one has almost completely broken down. The other sheet of plastic is partly shaded and has held together, it is currently experiencing a greenhouse effect with some plants growing underneath.

All the early summer rain has caused a large amount of goat heads plants (Tribulus terrestris) to sprout outside of the solarization area. I did my best to pick the plants but I had to violate my rule of not using chemicals and apply Roundup to a most of the back yard. My concern with using Roundup is the potential of creating weeds that are resistant to Roundup. Also, Roundup is turning out to be toxic.

This will be one of the few times I used chemicals to control weeds. Depending on how much time I have for the rest of this summer, I will try to apply more plastic to the backyard to take advantage of the late summer heat.

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Solarizing The Back Yard To Kill Weeds

With summer approaching, it’s time to start focusing on outdoor projects and leave the indoor projects for the winter. Even if the weather doesn’t want to cooperate. The previous owners of my house had a section of the back yard, about 1500 square feet, sectioned off to grow grass including an underground sprinkler system. When I moved in to the house it had been unoccupied for a while and the weeds had taken over. I tried growing grass where it used to grow but haven’t had success.

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The problem, the low water grass (buffalo grass, blue gamma, etc) I’ve tried growing can’t compete with the weeds. I refuse to use chemicals to kill the weeds and I’ve tried manually cutting down the weeds down and pulling them out but it hasn’t been effective enough (especially against the dreaded goat heads aka Tribulus terrestris).

I’ve discovered a chemical free method of eliminating weeds on a large scale called solarization. It uses transparent plastic directly on the ground to bake the soil and will kill seeds. It’s possible to cook the soil 6 inches deep and at 125 degrees ore more. The University of Arizona has a good article on the process for use in Tucson (also see Wayne Schmidt’s Solarization Page) and should adapt to New Mexico.

The timing for installing the plastic is good right now, it has just rained giving the ground a good soaking and the spring winds died off long enough to install the plastic. My first try was using 108 square feet of 1 mil painters drip cloth. The thinner the plastic the better the sun penetrates but 1 mill is too thin for this application. Even though I had cut down the weeds even a little bit of plant materials was able to puncture the plastic. Smaller sections of plastic are harder to manage than larger sheets.

I was able to find 500 square feet 4 mil plastic sheets at the local WalMart (as much as it pained me to have to enter the place). It wasn’t cheap at a cost of $20 per roll. I could have probably put a ad on craigslist and found some plastic sheeting for free but I have a limited window to install it.

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The installation of the plastic went well. I used bricks to hold the plastic down while I laid it out. I then dug a trench around the perimeter and used the dirt to seal the edges. I used two sheets and overlapped them about 6 inches using bricks and landscape staples. It’s important that air cannot get under the plastic sheeting so the moisture and heat stays under the plastic.

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I’m not planning on growing grass in the entire area where grass originally grew, only about 1000 square feet so two sheets should be sufficient. Since I will be out of town for most of the summer the ground should be well cooked by time I get back. I will try to make regular soil temperature readings during the summer.

Spring Is Nearly Here

The average last frost date in Albuquerque is April 15th. I’m not letting that stop me from getting an early start on my vegetable garden this year. Last year I made many mistakes producing lack luster results. That’s ok because I have learned from my mistakes and will hopefully produce a bountiful harvest this summer.

The overall size of the garden has increased to 120 square feet from 100 last year. I’ve changed the irrigation system to make it easier to manage. Last year I had a single soaker hose that snaked from row to row. It was hard to move around and get water just where I wanted. The hose itself sucked because it was a thin walled hose with holes every 12 inches. Again hard to get water just where I wanted. This year I have a single poly hose that runs along the inside wall. I can then connect smaller hoses to this hose along the perimeter anywhere I want. I’m already using 1/4 inch recycled tire hose which is a soaker hose that spews water all over it.

My biggest concern is lack of nutrients in the soil. I added amendments last year and added more this year but it’s just not going to be enough. To overcome this I will use compost tea. “Why go to the extra trouble of brewing, straining, and spraying a tea rather than just working compost into the soil? There are several reasons. First, compost tea makes the benefits of compost go farther. What’s more, when sprayed on the leaves, compost tea helps suppress foliar diseases, increases the amount of nutrients available to the plant, and speeds the breakdown of toxins. Using compost tea has even been shown to increase the nutritional quality and improve the flavor of vegetables.” I’m betting a lot on this so it better work as good as they say.