I had good luck with my raised bed for a while and had a few pest and disease problems. But one summer a raging case of wilt (I think Fusarium wilt) weakened or died quite a few of my plants (mainly peppers) and a colony of hungry fleas settled in my tomato field.
Coupled with California's severe drought, the extremely hot season of the year, and the upcoming holiday month, I've decided to put all these issues to bed - under a plastic sheet for the rest of the summer, through insurance, an inexpensive and most importantly manual process called ground solar radiation.
What is terrestrial solar radiation?
Soil disinfection is a highly effective, non-chemical method of controlling soil-borne diseases that spread through the top 6 inches of soil.
While commonly used on commercial farms, it is not as common in home gardens as it requires some or all of the soil to be fallowed in mid-summer. In a garden where space is often limited, it is difficult to do without a raised bed for the four to six weeks required to care for the soil.
But if you're planning ahead (or, like me, know you'll be away from your garden for a long time), solarizing your soil is the perfect solution for killing weed seeds, controlling nematodes and pests, eliminating of plant pathogens from the soil. and improving agriculture and soil biology.
Think of it as a solar oven in your garden that bakes everything underneath - and what comes out is barren soil, free of the problems that plagued your plants.
Benefits of soil solar radiation
By simply harnessing the power of the sun, solar radiation can remove most weed seeds from the soil, especially annual weeds. (Some perennial weeds, such as Johnson grass, may have deep roots or rhizomes that heat cannot reach.)
Intense heat also speeds up the decomposition of soil organic matter, releasing soluble nutrients such as nitrogen, potassium, calcium and magnesium, making them more available to plants.
Solar radiation disinfects the soil from fungal and bacterial pathogens that cause Fusarium wilt, Verticillium wilt, potato scab, southern blight, late blight, tomato cankers, roots, gall anddepreciation. (However, it does not work for airborne diseases such asgarlic rustor late blight).
The method is particularly effective against certain fungi, such as Fusarium wilt spores, which can live for many years in the soil and even in soil next to garden tools.
In cases where crop rotation fails to control plant diseases, solar disinfection is the easiest way to start from scratch, so to speak.
Soil solarization also reduces populations of nematode pests (such as root knots and daggerworms) and destroys the eggs, larvae and pupae of destructive pests (such as cucumber beetles and pumpkin borers).
But what about the good bugs?
So you read that solarizing the soil can get rid of all the bad bugs and germs, but what about all the beneficial organisms that make up the soil food chain?
Don't worry: it's believed that earthworms simply burrow deeper into the soil to escape the heat and return to the surface when conditions are ideal. As for beneficial soil organisms, many are able to survive solar radiation (eg mycorrhizal fungi, which are very heat resistant).
Yes, you will probably lose some of your arthropods and other soil dwellers as collateral damage, but once the process is complete, many organisms will begin to recolonize the soil quickly (such as bacteria and fungi that parasitize plant pathogens and stimulate the growth of plants).
Indeed, the increase in the number of beneficial microbes can make soil more resistant to pathogens after solar radiation (compared to non-sunlit or fumigated soil).
Thanks to this, plants grow faster, become stronger and healthier.
How soil disinfection works: timing is everything
Soil solar irradiation involves trapping solar energy under a thin plastic sheet to heat the soil to temperatures high enough to kill soil organisms.
Soil temperatures of at least 110°F to 125°F, held constant for at least four weeks in the top 6 inches of soil, will prevent the emergence of many annual weeds and mesophilic fungi, which make up the majority of soilborne pathogens. .
This means that ground insolation works best during the hottest month of the year when the days are long and the sky is clear, which for many zones occurs in the weeks before and after the summer solstice in June or July.
In central Oregon (where I live now), the hottest season is from mid-July to mid-August, when the daytime high can exceed 90°F and the nighttime low is around 45°F .
But in Southern California (where I first lit up a solarium garden), the hottest months are September and October, when strong Santa Ana winds blow in from the high desert and usher in the sweltering Indian summers (as well as the infamous fires).
As you can see, temperatures vary a lot, so it's best to check historical climate averages if you're not sure when your area is the hottest part of the year.
Soil disinfection is less effective in the spring, even if your garden is basking in the sun all day. The mild climate has little effect on soil-borne disease control, so it's not worth trying early in the year before you start planting.
But youhe canstart a little earlier if you have a small window of warm weather.
In my experience, even at a relatively mild temperature of 75°F, the first 3 inches of soil in my raised area (which was in the sun for most of the day) heated up to 116°F. In the weeks that followed, the temperature under the plastic also rose and the soil warmed deeper.
So for best results, determine the warmest window in your garden for four to six weeks and schedule your soil for sun exposure during that time.
How to make sunshine in the garden
1. Gear up or solo.
Before starting, remove all plants andfertilizergarden bed. If they are infested, bag them up and throw them in the trash.
For solar irradiation to be successful, the substrate must be smooth and flat so that the plastic can adhere firmly to it. Plow or turn the soil and remove or break up any clods, stones, branches and hard roots. You don't want anything on the ground that could tear or puncture the plastic.
I usually dig to the depth of the fork, but for heavy clay soils or soils that have not been cultivated for a long time, a depth of at least 30 cm is recommended.
Studies have shown that the addition of organic additives of animal or plant origin (such as aged animal manure orfence cultureresidues, especially brassicas, cover crops such as mustard) before solar radiation improves its effectiveness. The changes introduced not only increased the rate of heat generation in the ground, but also increased the heat transfer capacity. And when it comes to soil sunshine, more heat is always good!
A word of caution:I usually don't use horse or cow manure in my garden unless I'm 100% sure the animals have been fed herbicide-free hay or grazed on herbicide-free pasture. There is always the risk that herbicide residues in manure will affect or even destroy plant growth, and this is a riskVerydifficult problem to eliminate.
So, if you have composted chicken manure, rabbit manure, earthworms, bat guano, green manure, or well-aged kitchen compost, go ahead and add it to the top 3 to 4 inches of soil and rake in well.
When the ground is level, place a garden hose or sprinkler over the bed and water deeply. You want the top 12 inches of soil to be moist. Moisture transports heat faster and deeper into the soil, while making soil-borne pathogens more sensitive to heat.
2. Choose the right type of plastic.
Surprisingly, clear plastic is actually more effective than black plastic at warming the earth. The sun's rays easily pass through the clear plastic and are trapped in it to warm the earth. Black plastic, on the other hand, tends to absorb light but reflects little heat (cfUC ANR).
And while it may seem counterintuitive, the thinner the plastic, the better it traps and retains heat - that's why we don't use greenhouse plastic here.
Very thin plastic (1 mil) is the best choice, but can be susceptible to damage from birds, animals, or the weather. A good compromise is 1.5 to 2 mil plastic with weather or UV protection, as it will last long enough until you remove it from the bed.
Disclosure: All products on this site are independently selected. If you purchase from one of my links, I may earn a commission.
I used 2 mil plastic fabric (found at my local hardware store), but for larger gardens you can find bulk rolls of polyethylene at farm supply stores or online.
Recommended polyethylene sheet for ground solar radiation:
3. Cover the raised bed tightly and completely.
Cut the plastic to fit, leaving at least 8 inches of overhang on all sides. There are several ways to protect plastic:
- You can dig a trench along the inside perimeter of the bed and then bury the plastic edges 6 to 8 inches deep.
- You can secure the plastic with heavy objects (such as 2x4s, pipes, bricks, cinder blocks, or whatever else you have around the house) placed around the perimeter of the bed, making sure they are securely attached to the interior walls if you can. I want. covers the raised bed.
- You can sew plastic to a raised bed if the walls are made of wood.
I did this with a plastic seam and just wrap the corners of the bed like I would wrap a package. Clamps were inserted every 6 to 8 inches to ensure a secure seal, then several weights were placed on top of the plastic to hold it steady in any wind. (You don't want your tarp to turn into a sail during a summer storm!)
Weights can be bricks, cobblestones, sandbags, stones or similar small but heavy objects. Just watch out for sharp weights or those with rough edges that can cause pressure points that lead to tears.
The idea is to get the plastic to lie as flat as possible on the substrate, with few or no fins or holes that can let outside air in (and reduce the temperature under the plastic).
Immediately patch any holes in the plastic with duct tape and monitor your beds for four to six weeks if the plastic needs patching. (One morning I found holes in one of my tarps apparently caused by a raccoon running around the garden.)
If daytime temperatures are cooler than normal, you can increase the amount of heat generated in raised beds by adding a second layer of plastic over the first layer. Separate the mattresses slightly with PVC pipes, plastic bottles or other smooth objects that can run the length of the bed. This tiny pocket of air can add up to 10°F to the heat in the ground.
Maintaining the right temperature
Solar disinfection of soil is most effective when the top 6 inches of soil is maintained at a daily temperature of at least 110°F for four to six weeks, as most pathogens reside in this top layer.
If you don't have a soil thermometer to check, a meat thermometer will work in no time. I like to read in the middle of the bed during the day. then I just cover the hole with duct tape.
See all that condensation under the plastic? When I put my hand on the surface, I felt how warm it was down there. This is what you want every day.
Planting the garden after sunshine
After removing the plastic, you can sow seeds or plant seedlings as usual. To avoid bringing weed seeds to the surface, stick to shallow plantings and exercisegardening without diggingmethods.
No further soil treatment is needed. You're already starting from scratch with soil that has gained extra nutrients from sunlight, so compost can wait until mid-season (just drain or moisten the soil as needed).
To increase your chancesNOwhen re-contaminating soil, always start with uncontaminated pots and soil for planting and transplanting seeds, andclean your gardening tools, gloves and other accessories that frequently come into contact with your plants.
(No needdisinfect his feetby the way, every season - just pour the soil or rinse with water before storing or using.)
Frequently asked questions about ground solar radiation
Is it safe to sunbathe in the garden?
Solar radiation is known as a hydrothermal process. it takes place in moist ground covered with plastic and heated by sunlight during the hottest part of the year.
Compared to chemical methods of weed and pest control, such as the use of fumigants, solar radiation is environmentally friendly and can be used in organic gardens and around children and pets.
When is the best time for sunshine in the garden?
The garden should be exposed to the sun during the hottest four to six week period in your climate. varies by location. In general, the average daytime temperature must be at least 90°F for sunshine to occur.
What kind of clear plastic should be used for soil sunshine?
Thin clear plastic (between 1500 and 2000 with water resistance or UV resistance) is best for soil tanning as it is more effective at trapping and retaining heat. Choose a completely clear plastic rather than a frosted or milky appearance, as this will reduce the transmission of solar energy.
Can thicker plastic be used for soil sunshine?
Absolutely! If you have around 6000 greenhouse plastics (or recycled from other uses), you can use them to make soil sunshine. This process may take a little longer depending on how hot the weather is in your area, but it should be just as effective in controlling weeds and pests.
Can you use the black tarp to make the ground sunny?
Yes, you can use the black plastic tarp to make ground sunshine. When black plastic is used (instead of transparent plastic), the technique is called dazzling (compared to solar radiation). Hide can use any opaque cover color, and while it takes longer than sun disinfection, it can be effective as long as the soil temperature remains between 110°F and 125°F for at least four weeks.
Can you store plastic for more than six weeks?
When soil tanning, keep plastic wraps on for at least four weeks and a maximum of eight weeks - at which point effectiveness tends to drop and most plastic wraps begin to wear out.
Will soil disinfection kill nematodes?
Solar radiation can reduce populations of nematode pests, although nematodes are relatively mobile and can move deeper into the soil to escape the heat. Solar radiation is most effective for nematodes in the top 12 inches of soil. Any pest that lives deeper in the soil can survive exposure to the sun and return to destroy your crops.
Will soil disinfection kill bermuda grass and johnsongrass?
Bermudagrass and Johnsongrass can be controlled by solarization if the rhizomes are near the soil surface. In general, however, solar radiation is less effective on perennial than annual weeds because perennials tend to have deeply buried roots, shoots, rhizomes, or tubers that can regrow.
This post has been updated from an article originally published on September 6, 2014.
See web reference athow to sun the soil in the garden.
Solarization is most effective when done during the hottest weeks of the year. The best time for solarization of soil in inland California is from June to August, although good results may be obtained starting as early as late May or as late as early September in the southern California desert regions.How do I solarize my garden? ›
- Step 1: Clear garden bed of debris. Remove all plant material, weeds, and mulch material from the area to be solarized. ...
- Step 2: Wet the area. ...
- Step 3: Apply plastic. ...
- Step 4: Do nothing for 4 weeks. ...
- Step 5: Remove plastic and incorporate compost.
Before you can remove the plastic, you'll want to wait six to eight weeks for the soil solarization process to take place. After six to eight weeks have passed, you should have healthy soil that's ready for planting again.How do you solarize a new garden bed? ›
Soil solarization is a simple and inexpensive way to use the sun to prepare a garden for planting. Solarization involves watering a patch of soil, covering it with clear plastic, then allowing trapped heat from the sun to bake the soil to kill off weeds and pests.How long does ground clear stay in soil? ›
Ortho GroundClear Year Long Vegetation Killer is formulated to kill weeds and grasses and prevent new growth for up to 1 year.Should I add compost before solarization? ›
When you are solarizing open soil, try incorporating compost before solarization. Many studies suggest this can increase pest control. Controlling perennial weeds will likely require far more than two weeks of solarization.How do you remove dead grass after solarization? ›
Clear away dead grass where you plan to put walkways or otherwise need an even surface. Where the lawn is to become planting bed, just treat the dead stuff as compost. Plant into or mound soil atop it. Eventually, it will disintegrate either way.
If using plastic bags, fill them with soil and close tightly, setting them in a sunny location in the yard. Four to six weeks of solarization during the hottest part of the year should be sufficient to sterilize the soil. Areas with cooler, windy, or cloudy climates may be upwards of eight to ten weeks of solarization.What are the negatives of solarization? ›
This heating has a profound impact on soil microbial communities, and can cause the death of plant pathogens, especially those that cannot endure temperature above 37–40 °C. Similarly, the seedbank of weed seeds, as well as various insect and nematode pests, can be rendered non-viable through soil solarization.How long does it take to solarize weeds? ›
The solarization process will take 4-6 weeks, possibly 8 weeks. Heating can occur as deep as 18 inches with soil temperatures reaching 90-98 degrees at that depth. The soil temps will be around 108-131 degrees at 2” deep, and temps can reach up to 140 degrees in the top 6 inches.
Sufficient steam must be applied to maintain a temperature of approximately 160°F for a duration (dwell time) of 20 minutes. Steam application to soil has a similar effect to soil as soil solarization, although the length of time for treatment is much less for steam.How do you solarize old potting soil? ›
To solarize container soil, place in a black plastic bag or in covered five-gallons buckets and place in a sunny location for four to six weeks to kill off these unwelcome elements and prepare the soil for new plants.Why put cardboard in garden bed? ›
It's a great mulch, and prevents weeds from sprouting. Decomposing cardboard adds organic matter to the soil, improving your garden's drainage and boosting nutrient levels. Earthworms flock to the dark, moist, safe habitat cardboard provides, leaving behind a nutrient-rich layer of worm castings–free fertilizer!Should I put plastic on the bottom of my garden bed? ›
Avoid lining your garden beds with plastic, as this prevents drainage and could drown your plants' roots. If you have a weed and pest problem, consider installing a combination of metal mesh and fabric or hardware cloth and cardboard to get both benefits at once.Can you solarize with cardboard? ›
Steps Cut the grass as short as possible, then cover it with a layer of cardboard or a thick layer of newspaper. Make sure the pieces overlap to keep sunlight from reaching the soil. Thoroughly wet the cardboard to help it break down. Cover with at least 4 inches of mulch or compost.Will ground clear work if it rains? ›
If you find weirdly placed weeds, enlist the help of Ortho® GroundClear® Super Weed & Grass Killer to spot-treat them. When used as directed, it starts working immediately to kill weeds, and is rain-resistant within 15 minutes.Can you eat vegetables sprayed with Roundup? ›
Roundup has been linked to increased risk of bladder cancer, non-Hodgkin Lymphoma, prostate, and kidney cancer, and has been found to induce breast cancer cell growth. Glyphosate exposure has also been tied to cancer in dogs. Although Roundup may be OK around vegetables, you may want to stay away from it altogether.How do I permanently get rid of weeds in my garden? ›
Using Bleach to Kill Weeds Permanently
Apply one cup of bleach, undiluted, to the afflicted area. Wait until the weeds turn brown before pulling them out of the ground. Run water around the area to flush the bleach, especially if you are trying to grow plants or grass in that area.
Solarization is the process of placing a clear plastic tarp over an area to heat up the soil underneath. Occultation uses opaque coverings instead of clear. Occultation takes longer. The plastic traps heat and moisture, which encourages seed germination and plant growth.What goes first top soil or compost? ›
A well-dressed lawn or landscape will include layers of different materials that create an ideal environment for healthy growth. First is the topsoil, then the compost and, finally, a mulch to blanket it all. Topsoil is the layer of humus (partially decomposed organic matter) between the surface and the subsoil.
Dead grass usually looks the same as dormant grass, but it does not come back when the weather improves or when you take measures to revive it. If your grass is dead, you will need to reseed or replace the grass to once again enjoy a thriving, green lawn.What brings back dead grass? ›
There is no way to revive dead grass, but you can lay new sod to grow your landscape again from scratch. If you notice brown, bare, or thinning areas in your lawn, these are clear signs that you need to sow new seed or replace the sod.Can watering bring back dead grass? ›
It's a common misconception that watering dead grass will bring it back to life. The truth is, when you water dead grass, it can actually make the situation worse. It can cause the roots in the ground to rot and decompose faster than they would if left alone.How do you sterilize soil so nothing will grow? ›
– Rock Salt for Weeds
Once you have sprinkled the salt, wait for a few days for the salt to leech into the soil. After a few days, you will begin to notice the weeds dying. The salt will sterilize the area and prevent any further growth for years to come.
Heat. Heating the soil is very effective and the soil can be used immediately after cooling, unlike chemically treated soil. Many plant pathogens are killed by short exposures to high temperatures. Most plant pathogens can be killed by temperatures of 140°F (60°C) for 30 minutes.What is the biggest problem with solar energy? ›
The Disadvantages of Solar Energy
One of the biggest problems that solar energy technology poses is that energy is only generated while the sun is shining. That means nighttime and overcast days can interrupt the supply.
Always apply herbicides during the middle of the day when the sun is shining strongly to disrupt photosynthesis. Active spraying during the winter can also ensure that the weeds are not allowed to germinate properly before the arrival of spring.Do weeds grow more in sun or shade? ›
Weeds grow and eat purely based on the soil and the sun, unfortunately, they don't need both, they only need one. While they will always grow towards the sun, they don't require it to survive, which is why we are able to see them in the first place.How much sunlight do weeds need? ›
Cannabis plants are happiest when they get between 10–12 hours of direct sunlight per day. As you'll likely have witnessed with your own eyes, weed plants grow really vigorously, and hence need a ton of solar energy to fuel their growth.How do you sterilize soil to prevent weeds? ›
But for the curious, here's how you do it: Add soil to a baking pan (3 to 4 inches deep), cover with foil, and bake at 200 degrees F for 30 minutes or when the soil temperature reaches 180 degrees. Anything higher than that can produce toxins. Let cool. Keep covered to remain sterile.
- Add Compost. Compost is decomposed organic matter, and it is the best thing you use to improve the health of garden soil. ...
- Get a Soil Test. ...
- Mulch the Soil Surface. ...
- Prevent Soil Compaction. ...
- Rotate Crops Each Year. ...
- Grow Cover Crops. ...
- Add Aged Animal Manure.
There are four methods of growing plants without soil-water culture, sand culture, gravel culture, and adsorbed-nutrient technique.Can you reuse potting soil from dead plants? ›
If plants died from bacterial, fungal or viral disease, then you definitely do not want to reuse the soil, as soilborne pathogens can still be present and active. However, if the plants that grew in the soil before were healthy, it is generally OK to reuse the potting soil.What happens if you use potting soil in the ground? ›
Potting soil is a more suitable soil type for outdoor plants than garden soil. It's created with organic matter and additives to be a standalone soil for growing plants. However, it can get compacted and cause waterlogging and root suffocation when used for container plants.Does putting cardboard down stop weeds? ›
A single layer of cardboard is laid out over the areas of lawn no longer needed. When it eventually breaks down, the cardboard will add carbon back into the soil. A crack in the cardboard reveals hardy weeds making their way to the sunlight. Extra mulch will solve this issue.Why put cardboard under mulch? ›
Beneath the layers of compost materials, sheet mulches typically include a layer of cardboard to keep grass and weeds from growing through – a great way to smother unwanted vegetation or convert a sod lawn into a garden.Does cardboard keep weeds from growing? ›
Whether your raised garden bed ideas require a new form of weed control or you're battling weeds on your lawn, the cardboard will come in handy. 'It is thick enough to smother weeds, but unlike landscape fabric, it'll rot over time,' John says.What not to plant in a raised bed? ›
- Winter Squash.
You Can Use a Layer of Cardboard at the Bottom of Raised Beds to Prevent Weeds. If your budget doesn't allow for weed barrier cloth, you can add several layers of cardboard to the bottom of your raised bed before filling it with soil. The cardboard will decompose in about 4 to 6 months.How do you fill a raised garden bed cheaply? ›
Logs buried in the raised bed are beneficial because you won't need much soil. That's why using large logs can be one effective organic material for filling raised beds cheaply. You can find grass clippings, twigs, branches, logs, and other rotting materials. Then, place them deep in the soil.
In general, transparent or clear plastic is most effective for solarization, as the heating rays from the sun will pass through the sheet and be trapped to heat the soil below. Usually black plastic is less effective because it absorbs and deflects part of the heat, rather than trapping as clear plastic does.How long does it take to solarize soil? ›
Before you can remove the plastic, you'll want to wait six to eight weeks for the soil solarization process to take place. After six to eight weeks have passed, you should have healthy soil that's ready for planting again.How long does grass killer stay in soil? ›
It can persist in soil for up to 6 months depending on the climate and the type of soil it is in. Glyphosate is broken down by bacteria in the soil. Glyphosate is not likely to get into groundwater because it binds tightly to soil. In one study, half the glyphosate in dead leaves broke down in 8 or 9 days.How long does it take for dirt to absorb water? ›
Loam Soil is best. A combination of sand, silt, and clay particles, this soil absorbs water readily and is able to store it for use by plants. Loam absorbs water at a rate between 1/4 and 2 inches per hour. Sandy Soil, because it has very large spaces, absorbs water at a rate of more than 2 inches per hour.Is solarization bad for soil? ›
Solarization has also been shown to be effective in controlling many soil borne diseases, nematodes, and other soil dwelling pests. Similar to boiling water to sterilize it, super-heating the soil with this method can kill much of the bad stuff living in the soil.How do you sterilize soil so weeds don't grow? ›
You can use any type of salt on your soil to prevent and kill weed growth. Table salt, common salt and rock salt can all be effective since they are all made up of sodium chloride. The only vital difference is that table salt is fine, whereas rock salt is made up of coarse crystals.Is it better to burn weeds or Roundup? ›
Flame weeding is considered an organic method of weed removal. However, if the weather is hot and the fire danger is moderate to extreme, Roundup may be the better option to avoid accidentally starting a fire or risking fines from the local fire district or other government agency.Does Roundup poison the soil? ›
Does Roundup Poison the Soil? Roundup manufacturer Monsanto claims the use of their product is safe and does not result in toxic soil. However, one USDA microbiologist begs to differ. According to Robert Kremer, phosphorus-rich soil can result in glyphosate teaching into the groundwater and contaminating it.What breaks down glyphosate? ›
The primary breakdown product of glyphosate is aminomethylphosphonic acid (AMPA), which is also degraded by microbes in water and soil. According to the EPA, available data do not suggest that this compound poses any hazard distinct from its parent compound, glyphosate.What absorbs water quickly? ›
Sponges and cotton are examples of materials found at home that are very porous and absorb water very easily.
Lastly, medium grain sand is the best alternative because of its medium-fine particles. It can hold enough water allowing sufficient aeration and absorption. Also, it is the best sand that will prevent roots from rotting.How do you fix soil that doesn't absorb water? ›
Hard-packed clay soils and even garden soils can become crusted and resist wetting, letting water run off instead of absorbing it. To re-wet, repeatedly sprinkle the surface lightly, making sure there is no run off. Covering the surface with a mulch such as straw, leaves, wood chips, or compost will also help.