For a while I was lucky with my raised bed garden , and had few problems with plague and diseases . But one summer , a vicious case of wilting ( I ’m guess Fusarium wilt disease ) weakened or stunted several of my plants ( mostly peppers ) and a hungry colony of flea beetles had contain up manse in my tomatillo crop .
Combined with a severe drouth in California , a particularly hot season , and a month - prospicient vacation looming , I decided to put all those problems to bed — under a sheet of plastic for the rest of the summer , through a secure , inexpensive , and mostly pass on - off process forebode land solarization .
A chemical-free way to fix problematic soil
Soil solarisation is a highly effective , non - chemical method acting for controlling soilborne diseases that unfold in the top 6 inches of soil .
While it ’s commonly used on commercial farm , it ’s not as prevalent in home gardens because it does involve part or all of the soil to lay fallow during peak summer . In a home garden where space is often limited , it ’s hard to give up a raised bed for the four to six weeks it use up to treat the soil .
But if you design forwards ( or , like me , you know you ’ll be away from the garden for an lengthy period ) , soil solarisation is an ideal solution for killing weed seeds , controlling roundworm and pest , eliminating soilborne plant pathogens , and improving tilth and soil biological science .
Think of it as a solar oven in the garden , baking everything underneath it — and what comes out is aseptic soil , free of the problems that used to plague your plant life .
Benefits of solarizing your soil
Simply by using the power of the sun , solarization can rid the soil of most weed seeds , peculiarly those from one-year dope . ( Some perennial grass , like Johnson grass , may have mysterious roots or rhizomes that warmth wo n’t reach . )
The intense warmth also speeds up the decomposition of organic textile in the territory , thereby secrete soluble nutrients such as nitrogen , potassium , calcium , and Mg and constitute them more available to plant .
Solarization disinfest the soil of the fungal and bacterial pathogens that cause Fusarium wilt , Verticillium wilting , spud blackleg , Southern blight , early blight , tomato pestilence , club base , crown gall , anddamping off . ( However , it does not mould on airborne diseases , likegarlic rustor former blight . )
The method is especially effectual for certain fungi , such as the spores that do Fusarium wilt , which can live for many years in the soil and even in the soil cling to your garden tools .
In these types of cases where crop gyration ca n’t ensure plant diseases , solarization is the easiest way to get over with a unobjectionable slating , so to speak .
insolate your grime also come down populations of pest nematodes ( like root knot and dagger ) and destroys the eggs , larvae , and pupa of destructive pestilence ( like cucumber beetle and squash vine bore bit ) .
But what happens to the good bugs?
So you ’re read that dirt solarization can get rid of all the bad germ and microbes , but what about all the good organisms that make up the soil solid food web ?
Not to vex : It ’s consider that earthworms just tunnel profoundly into the soil to escape the heat , and come back to the control surface when circumstance are ideal . As for good filth organisms , many of them are able to survive solarization ( such asmycorrhizal fungus , which are highly warmth tolerant ) .
Yes , you will probably fall back some arthropods and other surface soil inhabitant as substantiative impairment , but once the process is complete , many organism set out to speedily recolonize the stain ( such as the bacterium and fungi that parasitize industrial plant pathogen and rush industrial plant increase ) .
In fact , the increase numbers of good microbes can make the ground more resistant to pathogen after solarisation ( versus non - solarized or fumigated dirt ) .
As a resolution , plants grow faster , get stronger , and continue sizable .
How soil solarization works: timing is everything
Soil solarisation solve by trapping radiant energy from the Lord’s Day under a lean charge plate tarpaulin to wake the land at temperature high enough to shoot down soil organisms .
Soil temperatures of at least 110 ° F to 125 ° F , held steady for at least four weeks in the top 6 column inch of soil , will prevent the emersion of many annual weeds and mesophilic fungi , which are the majority of common industrial plant pathogens .
That intend stain solarization works well in the hot month of the class when mean solar day are long and skies are clear , which for many zones is the few week before and after the summer solstice in June or July .
In Central Oregon ( where I survive now ) , our red-hot geological period is mid - July to mid - August when daytime heights can exceed 90 ° atomic number 9 and nighttime low are around 45 ° degree Fahrenheit .
But in Southern California ( where I first solarize my garden ) , the hottest months are September and October , when strong Santa Ana fart blow in from the high desert and usher in swelter Indian summers ( as well as notorious wildfire ) .
As you may see , temperature vary wide so it ’s best to reckon at historical weather averages if you ’re not certain when the live part of the year is in your area .
Soil solarization is less effective in the spring , even if your garden is bathed in sunshine all daylight . The modest conditions does little to see soilborne disease , so it ’s not deserving the exertion to try early in the yr before you start your planting .
But , youcanstart a slight before if you have a short window of hot weather condition .
What I ’ve establish from experience is that even with a relatively modest heights of 75 ° F , the first 3 inches of grease in my raise bed ( that get full Sunday for most of the day ) heated up to 116 ° F . As the temperature of the air increase over the next few weeks , the temperature under the charge plate also increase and heated the grime more deep .
So for good final result , determine the hottest four- to six - week windowpane in your climate , for your garden , and be after to solarize your soil in that time .
How to solarize your garden
1. Prepare the soil.
Before you begin , remove all the plants andmulchfrom the garden seam . If they were affect by disease , bag and trash them .
For successful solarization , the soil should be smooth and flat to countenance the plastic to lie snug against it . Till or flex over the soil and take out or break up any clods , rocks , stick , and operose roots . You do n’t want anything in the stain that could potentially tear or deflate the plastic .
I typically dig to a astuteness of a branching tine , but for intemperate cadaver grease or soils that have n’t been cultivated in a while , going at least 1 foot deep is recommend .
Studies have establish that adding constitutive animal- or flora - based amendment ( such as of age animal manure orcover cropresidues , specially Brassicaceae cover craw like mustard ) before solarise improves its efficacy . The amendments not only increased the pace of heating generation in the soil , but also its heat - post mental ability . And when it comes to soil solarization , more heat is always a good thing !
A Good Book of warning : I typically do n’t use horse or cow manure in my garden unless I ’m 100 per centum sure the animals were feed herbicide - gratuitous hay or grazed on herbicide - complimentary pastures . There ’s always a risk that herbicide residue in manure can affect or even ruin plant life growth , and it ’s averyhard job to get disembarrass of .
So , if you have some composted chicken manure , rabbit manure , worm castings , bat guano , unripened manure , or well - aged kitchen compost , go in advance and incorporate that into the top 3 to 4 inches of soil , and rake it in well .
Once your soil is smooth over , localise your garden hosepipe or irrigation system over the bottom and water deeply . You want the top 12 inches of soil to be damp . The moisture conducts heat faster and deeper into the dirt , while gain grease pathogens more sensitive to the heat .
2. Choose the right kind of plastic.
Surprisingly , absolved plastic is really more effective than opprobrious plastic at heating up ground . The sun ’s rays well go along through clear plastic , only to be trapped inside to heat the grease . sinister credit card , on the other handwriting , tend to absorb light but deflect part of the oestrus ( concord toUC ANR ) .
And though it might seem counterintuitive , the thinner the credit card , the better it captures and trap the hotness — so we ’re not using nursery plastic here .
Very thin plastic ( 1 mil ) is the practiced option , but may be susceptible to price from birds , critters , or the element . A good via media is 1.5 mil to 2 mil charge card with weatherproofing or UV electric resistance , as it will last long enough until you remove it from your layer .
Disclosure : If you shop from my clause or make a leverage through one of my links , I may receive commissions on some of the products I recommend .
I used a 2 milliliter plastic drop cloth ( plant at my local computer hardware memory board ) , but for larger garden , you could discover bulk rolls of polythene from farm provision stores or online .
advocate polyethylene sheet for soil solarisation :
3. Cover your raised bed tightly and completely.
Cut the plastic to outfit , leaving at least 8 inches of overhang on all sides . There are a few way to insure the plastic :
staple fibre gun the plastic is the way I did it , and I but twine the corners around the layer as if I was wrapping a package . Staples proceed in every 6 to 8 inch to ensure a secure cachet , and then a duet of weights were laid on top of the plastic to keep it stable under any wind . ( You do n’t need your tarp to become a sail during a summer storm ! )
The weights can be bricks , pavers , sandbags , Isidor Feinstein Stone , or likewise small but heavy target ; just be careful with sharp or rough - edged weight that could cause pressure dot , leading to tears .
The idea is to keep your plastic as flat against the land as potential , with fiddling to no flaps or openings that could have in outside air ( and minify the temperature under the plastic ) .
patch up up any hole in the charge plate immediately with duct tape measure , and keep an center on your beds throughout the four- to six - week period in case the plastic needs patching . ( One morning , I found a few holes in one of my tarpaulin that had apparently been triggered by a racoon running through the garden . )
If your daytime temperature are cool than normal , you’re able to increase the amount of passion generated in your advance bottom by add a second layer of plastic over the first layer . break up the layer slightly with PVC pipe , belittled plastic feeding bottle , or other smooth objects that can launch the full duration of the bed ; that small pocket of atmosphere can increase the heat in the soil by as much as 10 ° farad .
Maintaining the proper temperature
Soil solarization is most effective when the top 6 inch of soil is maintained at or above a daily temperature of at least 110 ° atomic number 9 for four to six weeks , as most pathogens reside in this upper layer .
If you do n’t have a soil thermometer to test this , a pith thermometer will figure out in a pinch . I like to get a recitation in the eye of the 24-hour interval right in the midriff of the seam ; later on , I just piece the hole with duct tape measure .
See all that condensation under the plastic ? When I put my hand on the surface , I could feel how hot it was under there . That ’s what you want , every single sidereal day .
Planting your garden after solarization
After remove the plastic , you may sow seeds or flora transplants like normal . To avoid add any surviving gage seeds to the open , amaze with shallow plantings and practiceno - gibe gardeningmethods .
There ’s no need to further domesticate the dirt . You ’re already start sweet with grunge that ’s gained additional nutrients from solarisation , so fertilizer can wait until midway through the time of year ( simply do a side fecundation or soil drench as demand ) .
To ameliorate your luck ofnotreinfecting the soil , always start with unpolluted flowerpot and soil for seed begin and transplantation , andclean your garden tools , gloves , and other accessories that frequently total in contact with your plants .
( You do n’t have todisinfect your potsevery time of year , by the mode — just knock down out the soil or rinsing with water before storing or using . )
Read next : DIY Tool Cleaning Station : The truehearted Way to Clean Garden Tools
Common questions about solarizing your soil
Is solarization safe to use in the garden?
Solarization is what ’s known as a hydrothermal process ; it happens in moist soil that ’s covered with charge card and heat by exposure to sun during the hottest part of the year .
equate to chemical method of skunk and pest control , such as using fumigants , solarisation is environmentally friendly and can be done in organic gardens and around child and positron emission tomography .
When is the best time to solarize the garden?
You should solarize the garden during the hottest four- to six - week weather point in your climate ; this will vary by location . In universal , intermediate daytime temperature should be at least 90 ° fluorine for solarisation to come about .
What type of clear plastic should be used for solarizing soil?
A thin clean-cut credit card ( between 1.5 mil to 2 mile with weatherproofing or ultraviolet radiation opposition ) is effective for solarizing soil , as it ’s more effective at capturing and trapping heat . Choose a completely transparent plastic , rather than one with a frosted or milky appearances , since that will melt off solar energy infection .
Can you use thicker plastic to solarize soil?
dead ! If you have some 6 mil greenhouse charge card laying around ( or reprocess from other U.S. ) , you’re able to expend that to solarise your soil . The appendage may just take a little longer , bet on how hot the weather is in your area , but should be just as efficacious at controlling weeds and pests .
Can you use a black tarp to solarize soil?
Yes , you could use a dim plastic tarp to solarize territory . When mordant charge plate is used ( rather of unclouded plastic ) , the proficiency is called occultation ( vs. solarization ) .
Occultation can use any color of opaque cover , and while it takes longer than solarization , it can still be efficient as long as soil temperatures rest at 110 ° F to 125 ° F for at least four week .
Can you keep the plastic on for longer than six weeks?
When solarizing soil , you should keep charge plate cover on for at least four weeks and up to eight weeks — at that stage , efficaciousness tends to level off and most plastic tarps set about to deteriorate .
Will soil solarization kill nematodes?
solarisation can thin out populations of pest nematodes , though nematodes are comparatively nomadic and can move deeper into the soil to escape the heat . solarisation is most effective on nematode within the first 12 inch of grunge ; any pests living deeper in the soil may survive solarization and pass to damage your crops .
Will soil solarization kill Bermudagrass and Johnsongrass?
Bermudagrass and Johnsongrass can be controlled by solarization if the rhizomes are close to the grime control surface . In general , however , solarisation is less effective on repeated weeds than one-year weeds because perennials normally have profoundly buried roots , corm , rootstalk , or tubers that can resprout .
This post update from an article that originally appeared on September 6 , 2014 .
