Earth holes: A experiment in Guerrilla irrigation

[maiako]

Good article,bro.

 

[BACKCOUNTRY]

Cacadia-Thanks!

silverback- Yeah, painting will make the boxes last a bit longer, it would be a good approach when using lower quality materials. My plan will be to make my final design from either Western Red Cedar(a very rot resistant wood often used for making decks and planters) or perhaps from metal or or other strong non-wood material, it would be tempting to use pressure treated lumber except for all the very toxic poisons used to make them rot resistant.

Over saturation should not be a problem when using the Capillary action of the Earth hole devices, since the soil can only take what it can hold. Over saturation usually only occurs when water is added manually, especially in containers that cannot drain fast.
In Capillary action only the soil molecules themselves can hold moisture, so water cannot pool in large quantity between the molecules as is happening in a over saturation situation, which displaces oxygen in the soil and leads to suffocated roots(other wise known as water logging).

maiako- Thanks man!

Now that I have my plan as far as irrigation devices go, its time to locate my holes, as I find them I plan to treat then with Dolomite so it can adjust the soil PH over the rest of the Winter/Spring, and be ready for fertilizers and planting in May. Lots of footwork to do!

I am also planning to try a couple Blumat devices, and a couple small timer based devices this summer.

 

[jakeh]

I've got a question on this that may apply more to swamp growing. Where I am I hit water by the time I dig 10 inches this time of year and 2-3 ft later in the year. I was going to use Silverback's gorilla collar but I am thinking of getting a post hole digger and going down 4 ft then dropping one of 4" pvc pipes with an end cap at the bottom and holes drilled in the sides of the pipe. To keep mud from clogging the pipe I will wrap it with the weed block fabric and hopefully have a constant source of water trickling into the 4" pipe(checking the ph today). My question is:
If I made a T with the vertical part of the T being 1" pvc drilled with holes and filled with silverbacks zorbie dropped down into my 4" pvc self filling rez do you think it could wick enough water to the horizontal hole drilled, zorbie filled pvc that would be above the ground in a mound of dirt that I plan to plant in?
Since my horizontal piece of this system is the same as the bottom part of the gorilla collar I am thinking about just making a bunch of gorilla collars with this one modification to be able to feed nutrients although I may just do the T with time released nutrients on top of the soil.

 

[smokeymacpot]

ya thats where i meant for the water crystals to be, in the peat mix that will be in your bucket/wick, it really sucks moisture in so i expect it would help carry some upwards, should the wick not work as well as you hope it would. wouldnt need alot, maybe 2 or 3 spoonfulls.

 

[BACKCOUNTRY]

Yeah, putting them in the wick couldn't hurt, but the wick should work regardless, hundreds of thousands of Earthbox users will testify to that.

jakeh- I sent you a PM about your question last night but just realized you don't have enough posts to open it. I'm not sure what to tell you exactly on that one, I do have to say that even when the water table is at its lowest in your situation(2'-3' deep), it is still very shallow, your plants should be able to find it on their own with their roots, I don't think you should need to worry about using any irrigation devices, unless you want to use Silverbacks collar for feeding. Otherwise they should be able to forage on their own.

 

[Lt. Herb]

Well, after taking into account that the tub won't hold up underground without more modification than is practical, I've decided to go another route with the model I test this season, seeing as how I have neither materials, money nor manufacturing skill to construct a suitable/workable box.

The new variation is to use a 5 gal bucket with a single 2-4" pvc wick in the center of the lid (and a fill tube reaching to the surface somewhere of course). I am concerned that with a single wick of such a small size I may not get enough capillary action going to properly wet the soil in the root zone. To compensate I will try stuffing some panty-hose with vermiculite/peat/other wicking agent, stuff it down the pvc (instead of packing the pvc directly) into the reservoir and have a foot or two hanging out the top of the pipe to be buried in the soil. This provides a filter of sorts in the reservoir and allows for the wick to be 'pigtailed' around the hole before it's covered or directed straight up to where the roots will be when transplanted. I'm hoping the roots won't have any problem penetrating the hose, thereby allowing them to tap the core of the wick and then run for the res.

Assuming this design works, you could place multiple buckets in a single hole to up the water capacity for a site. The reservoir volume for each bucket is 5 gal. minus the volume of the wick, which is determined by the size pvc used and the height of your bucket. Most of the 5 gal buckets I have around are roughly 18" deep, so that's the value I've used for my estimates below:
2"pvc @ 0.1632gal/ft => 0.2448 gal wick / 4.7552 gal res
3"pvc @ 0.3672gal/ft => 0.5508 gal wick / 4.4492 gal res
4"pvc @ 0.6528gal/ft => 0.9792 gal wick / 4.0208 gal res

At the moment I'm leaning toward the 3" option as two buckets yield about 9 gallons total free water and hopefully enough of a supply as to achieve the goal of 3-5 weeks between visits.

 

[BACKCOUNTRY]

Yep, a very good idea, multiple devices, the only downfall(and its a extremely small one) is that you will be checking and filling 2 reservoirs instead of 1.

One thing I am still working on in my mind is what would be the deepest reservoir/wick length that will still transfer water through the wick without being overcome by gravity? I would like to assume that your wick could be more than 12" long, and 3" wide and still work. Perhaps the wider the wick, the further water can travel up? I just don't know, I'm no scientist.

Not knowing all the dynamics of wicks has lead me to make my designs with wicks as wide as possible, and short as possible, giving the water the quickest ride possible to the plants roots. This is why my more complicated box device is so wide and short, with one huge wick, my feeling is this is the optimal shape and ratio.

However, in the interest of simplicity, my Tub and bucket is made from inexpensive, easy to find materials, and as opposed to the Box device is actually fairly tall compared to its height. This was necessary to make the device cheap and simple.
I feel it will work well(maybe not optimal), and even if the water levels drop to where the wicking action to the rest of the hole slows, I believe the plant will grow roots to chase the water level down into the device, sustaining the plant until refill can occur.

This really is a experiment! I have no idea(yet) if the devices will work as I intend, which would be to supply moisture to the entire root zone of the planting hole, or at least whether or not it will still do this even when the device is below 75% of water capacity.
What I do know is that the plant will grow roots into the devices, and even though this is not the way the plant is intended to be watered, the plant should still be able to tap into it. So basically what I am saying is that even if the devices don't work as intended, the plants should still benefit, and should not die of thirst as long as a gallon or two of water still left when you return to refill.
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Lt. Herb- What would be the advantages of using two buckets in the box style, over using the Tub & Bucket style of Earth hole devices? The Tub & Bucket will have slightly more water capacity, and has about 4 times the wicking surface?

One advantage I could think of right off the bat would be packing size, the two 5 gallon buckets will fit inside each other, with the Tub & Bucket you are hauling a 18 gallon tub and a bucket. This could make a difference if you are needing to get these past watchful eyes, or have to pack it a long ways over rough terrain.
Installing the Two buckets won't save you much hole space though, the dimensions of the hole would still be pretty close.

 

[BACKCOUNTRY]

Growers that are interested in trying a Earth hole need not be intimidated by the involved build on the Box design, by starting with the Tub & Bucket design a grower could create a shrunk down design that would be easy to install and haul, all you need a tub and a sturdy container the same height or shorter to contain the free water, and of course a fill tube.

 

[Lt. Herb]

You nailed it BC, hauling tubs around was just a little too iffy in my situation. Other than that small modicum of security, you gain nothing and lose water capacity and wick surface for about the same amount of work to get it installed. I'm not entirely convinced that the single, smallish wick will be adequate either.

Then it occurs to me that the tub and bucket principle could be accomplished by using plastic garbage bags doubled up instead of the tub (think the big yard sized bags for leaves and such rolled down to the top of the bucket). More of a pain in the ass to get situated and you'll surely get your hands and knees a good deal dirtier than just dropping a tub in the ground, but it should provide the same function as the tub (keeping the water where the roots can get to it). Not only will the bags fit in your pocket, but it allows one to modify the 'tub' to fit oddball containers one might have lying around.

 

[BACKCOUNTRY]

You nailed it BC, hauling tubs around was just a little too iffy in my situation. Other than that small modicum of security, you gain nothing and lose water capacity and wick surface for about the same amount of work to get it installed. I'm not entirely convinced that the single, smallish wick will be adequate either.

Hmmm, the Box device has a 10'x10" wick surface area, about equal to the surface area of five 4" pipe wicks or seven 3" wicks, the tub and bucket has a wick surface that is many times that, you do understand that the tub is the wick in the Tub and Bucket right? The bucket is not a wick.
At any rate, there is no shortage of wick surface area in either of my prototypes.

Then it occurs to me that the tub and bucket principle could be accomplished by using plastic garbage bags doubled up instead of the tub (think the big yard sized bags for leaves and such rolled down to the top of the bucket.

Nope, nope! How are you going to keep burrowing animals like Gophers and Moles from digging holes through the bags? Thats why I used the Tub!

I've put alot of thought into this, and I have to say that if there is a apparently easier way that I am not using, there is probably a reason why. Just like above where I explained why I didn't build the box from a plastic tote box, even though at first it seems like a much easier way.

Keep your mind rolling man, this is how you learn.

 

[BACKCOUNTRY]

My estimation is that both of my Earth hole designs should sustain a plant(a 4-8oz yielder) 3 weeks during the hottest days of my summer between fillings.

My peak summer months are typically between July 7 and Sept 7, highs are usually in the 90s with 100+ days a common occurrence, sometimes for a week at a time. This is also the driest period of time, rainfall totals are rarely more than 3" for that period, and many years its zero, cloud cover is also rare, with most days clear as a bell.

The first part of my estimation is based on personal experience, from hand watering. In 2007 I lined many of my holes with plastic sheeting(like I will with the Earth holes), to see how much it helped with watering efficiency, leaving only a 6"x6" hole in the bottom for excess rain water to escape.
It did help alot, my plants grew faster with the same amount of water, and only one planted on a particularly hot hillside had problems with any heat stress.

For plants that yielded 4-5 oz, I gave about 2 gallons per week, applied directly to the hole, with no attempt to introduce it straight to the root zone, which I believe will make the Earth hole idea even more efficient.
So 2 gallons per week during the hottest days yielded 4-5 oz per plant at the end of the season. The Earth hole devices contain 10 gallons, 10 divided by 2= 5 weeks, no this assumes that the plant stays in the more moderate 4-5 oz size range, if they went bonkers and got huge, they would probably use the water lots faster, so lets say 3-5 weeks for this estimation.
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My second estimation is based on data collected by one of my favorite vegetable gardening authors, Steve Solomon. Steve used to live in my region, and did small scale farming in many places in western Oregon, and wrote many books that are beneficial to food gardeners in my region, and beyond.

Steve wrote alot about gardening in hot, dry climates like mine. He even developed applicable strategies for growing with almost no irrigation at all, in his studies he came up with figures for estimating the watering needs of intensely cultivated vegetables in various climates during the summer months.

If you would like to read up more on Steve, here is a link to his website, this link will take you directly to the online version of his book " Gardening Without Irrigation: or without much, anyway" - http://www.soilandhealth.org/03sov/0302hsted/030201/03020100frame.html , Silverback may find alot of good info to support his Gorilla collar in the pages of this book, look at info concerning "Fertigation", which is basically a way to grow plants in droughts using regular applications of water soluble fertilizer.

Any ways, Steve determined that in Hot(dry) climates like SW Oregon and Nor-Cal, at the hottest temps of the summer, a given patch of vegetables will draw about .35" of water from the soil per day, a little under 2.5" per week.
Now, my holes will be about 1.75'x1.75', about 3 square feet of surface area, a inch is about .083 of a foot, so .083'(1 inch of water) x 1.75 x 1.75=.25 cubic feet, .25cuft x 7.5 gallons per cubic foot=1.9 gallons.

OK, so say at mid summer my plants are using 2.5" of water per week, thats 4.75 gallons of water a week, meaning my device may last only 2 weeks until emptied. Of course Cannabis is much more drought resistant than most lush garden veggies that Steve used to determine his figures, and also just because the free water in the device is all soaked up doesn't mean that all the moisture in the soil of the hole is, so I'd say the overall potential of the Earth hole should be 3 weeks or longer for sustaining a moderate sized plant in the worst months of summer, before any signs of wilt begin.

Of course I won't be planting in total full all day sunshine like vegetables in a field are, there will be trees around to provide camouflage, I will make sure the plants get plenty of sunshine to produce the quantity of bud needed, but there should be enough shade provided at the ends of the day that field crops don't usually get. So its likely that Cannabis plants in my plots will use less than Steve would predict for field crops.

Of course I have to try it to see, but at least I have reasons to believe I will be successful.

If my devices don't reach the desired 3-5 weeks at all parts of the season, I will simply make them bigger until they are big enough.

 

[Lt. Herb]

Just a quick bit I found about capillary action in soils:

Soil Water Storage

Within the soil system, the storage of water is influenced by several different forces. The strongest force is the molecular force of elements and compounds found on the surface of soil minerals. The water retained by this force is called hygroscopic water and it consists of the water held within 0.0002 millimeters of the surface of soil particles. The maximum limit of this water around a soil particle is known as the hygroscopic coefficient. Hygroscopic water is essentially non-mobile and can only be removed from the soil through heating. Matric force holds soil water from 0.0002 to 0.06 millimeters from the surface of soil particles. This force is due to two processes: soil particle surface molecular attraction (adhesion and absorption) to water and the cohesion that water molecules have to each other. This force declines in strength with distance from the soil particle. The force becomes nonexistent past 0.06 millimeters. Capillary action moves this water from areas where the matric force is low to areas where it is high. Because this water is primarily moved by capillary action, scientists commonly refer to it as capillary water. Plants can use most of this water by way of capillary action until the soil wilting point is reached. Water in excess of capillary and hygroscopic water is called gravitational water. Gravitational water is found beyond 0.06 millimeters from the surface of soil particles and it moves freely under the effect of gravity. When gravitational water has drained away the amount of water that remains is called the soil's field capacity.

Figure 8l-1 describes the relationship between the thickness of water film around soil particles and the strength of the force that holds this water. Force is measured in units called bars. One bar is equal to a 1000 millibars. The graph also displays the location of hygroscopic water, the hygroscopic coefficient, the wilting point, capillary water, field capacity, and gravitational water along this line.

There was another paper on landscaping that had to do with run off and how water moved through soil, but I can't find a link at the moment. However, it basically stated that the finer the soil, the farther it could wick water away from the water table. Clay soils wick the slowest but also will wick water the farthest, lighter soils will wick the water away faster, but won't take it as far, therein lies the trade-off.

 

[Some1here]

Cool!

Cool!

Hey BackCountry great idea for the Earthbox mod. I will be making 1 with your design and 1 using rope for wicks. I found that a 18 gal bin cut in half horizontaly fits almost perfect inside a 30 gal bin. Both halves will work great for the water reserve for each bin. I'm just wondering how many rope wicks I should use to give the plant enough water. I'm thinking one wick near each corner and one in the center. Think that would be to much or not enough?

 

[BACKCOUNTRY]

Nice find there Lt.Herb!

Some1here- I'm not sure how to judge the capillary potential of rope wicks, I'm sure they can work, but how far they can move water, and number needed is unknown.
One reason I moved away from rope wicks in my design was seeing how well soil wicks work(via the Earthbox), I also like the fact that the roots of the plant can grow into the soil wicks and establish direct contact with the reservoir, impossible in rope wicks.

My advice to you would be to use many wicks, like dozens, and don't expect the wicks to transfer water very high.

 

[#1cheesebuds]

this was i very cool thread to read.

so would this work in the backyard as well. I am thinking yes all the way.
I may try to build me one for my 2009 summer outdoor grow.

 

[Some1here]

Nice find there Lt.Herb!

Some1here- I'm not sure how to judge the capillary potential of rope wicks, I'm sure they can work, but how far they can move water, and number needed is unknown.
One reason I moved away from rope wicks in my design was seeing how well soil wicks work(via the Earthbox), I also like the fact that the roots of the plant can grow into the soil wicks and establish direct contact with the reservoir, impossible in rope wicks.

My advice to you would be to use many wicks, like dozens, and don't expect the wicks to transfer water very high.

Thanks BACKCOUNTRY I'm thinking I'll drop using the rope wicks and try something else. Hmmmm. I got my thinking cap on and many ideas are going through my brain. Let you know what I come up with...... if anything

 

[BACKCOUNTRY]

Hey guys! I'm getting bits of prep-work done on this years crop as the weather allows. It looks like I'll be trying 4 Earth holes this year, 2 will be placed in my typical well hidden in the tree line type plots, and 2 more will go into plots with tons of sunshine, this way I can test them in both extremes.

Doesn't look like I'll have many clones to try this year, I'll probably use mostly sexed seedlings, my indoor growing buddy is having his own problems and had to put a end to our project to find the perfect clones for this year, but thats fine.

Two more months and my girls start hitting the soil!!

 

[Robin_of_Loxxy]

I like this allot. I am thinking the easiest method would be a large contractor trash bag for the liner and just a bucket and dipstick, no tubs or baffles fuck it. I made up a pic but I can't upload right now for some reason.

 

[BACKCOUNTRY]

Yeah, that would be simple, and it may work for some situations, but more challenging situations often demand more complicated answers.

 

[SevenSeeds]

I've always read your thread and outdoor season is coming up, so i'll be around highest respect to you BackCountry for all your hard work on these forums, and obviously the tough growing you do! Much inspriation from people like you,

Anyways to actually add to the thread....I was thinking of cheap/big res...and also digging can be a problem for alot of people, many different ways....since a "kiddy pooL" plastic, cheap, very big res...its just sketchy carrying into the woods heh...Im trying to think of something that could be less to carry maybe a tarp anyways great ideas but I dont have to tell you that you already know your BC! peace dude see you around