Tilling - Double-Digging? Need Advice

[Joe98]

Putting in my first organic vegetable garden next year, so forgive me if my questions are a little naive. I'm trying to get everything tilled up now and let it rest all winter. I've skimmed several books, one of which mentioned "Double Digging" tilling. Here's a parphrasing of the process:

Dig a 1 foot trench down the long side of the garden. Keep the top soil in the garden, but take the rest and throw it in a wheel barrow. After finishing the trench, go back and dig down another foot of subsoil and put it in the wheel barrow. (Sounds like a big wheel barrow). Mix the subsoil with peat moss and compost before putting it back in the garden. Make the mixture one third peat moss plus two thirds compost, plus one part subsoil. Rake the top soil back into the trench, then add the new subsoil mix on top. Dig another 1 foot trench and repeat untill garden is all tilled. Tamp down when finished. Expect bed to be about three inches higher when finished. Wait at least a month before planting.

Bascially, I wanted to ask the group if this seems like a sound method. I'm in western PA and my soil tends to be on the clay side. I don't think I'll go as deep as two feet, but because the garden area is new, I do plan to go deeper than one would for standard tilling. In particular, does the mix sound right? BTW, when they say peat moss, am I to assume they mean peat hummus? And for compost, I expect to use mostly manure (bags). Is it reasonable to assume the bed will only be rasied 3 inches?

There is still some grass on the plot I plan to use, and with winter coming soon, I doubt I'll have time to cover it and kill it with black plastic. If I just till the grass under, and then cover it and let it sit all winter, I should be fine, right?

Oh, this might be a dumb question, but... If putting black plastic over grass for a couple weeks kills the grass, why doesn't the grass die when covered by snow all winter?

[Jim W]

Answers answers..

Double digging is double digging, 'tilling' done with a tiller, is a mechanised version of hand digging (a bit like ploughing) I suspect the book may have UK terms in some of its origin. Peat moss is not incorrect though I guess Moss Peat; that is, peat made from moss, is what is referred to. It is humus as you describe.

The moss is just used to add humus.. You could equally add mature leaf mould (2 - 3 year) or similar.

Compost can be of your choice. Matured animal manure is fine as is home made compost (from kitchen waste etc). AS long as its partly rotted eg NOT fresh. Digging is often measured in the length of a spades blade or 'spits' so you can substitute 'spit' for 'foot' in the measurements. Though I guess it depends on how big a spade you use!-)

You can adapt double digging like this.

Remove your first spit depth trench of soil and move it to the 'end' of the are you intend to dig. Fork manure/humus/compost into bottom of second spit spit of soil.

Fill first trench with soil from 2nd and continue this method across the area to be dug. When you reach end of the area you will have your soil from your initial trench to fill in.

Lift the turf and stack upside down, covered under plastic. Next year you will have a ready made loam pile for potting etc.

Snow lets through enough air and light and is naturally cold so minimises growth. Black plastic only cuts out light and air.

// Jim

[Louis Ohland]

Having used a tiller for some years, I'd advise only using it to prepare the bed. It really beats using a shovel in heavy soil. Make the trench, amend the soil, put the soil back.

I stopped using the tiller on my prepared beds, let the soil create a structure again. If I was to add further compost, then I'd consider using the tiller again... But it's a bit hard to lift the 6HP Troybilt high enough to get into my beds.

[Joe98]

Thanks for the help Jim,

I have a little "home made" compost, but the rest will be store bought bagged manure, which is certainly rotted.

But the rotted manure IS the compost, right? And is the two thirds compost

• one third (peat moss) humus about right in your opinion?

Hmm... What you suggest sounds like a good tip for making good loam, but is that necessary? As I said, I have grass on the area designated for the garden but it's spotty and useless as sod. In the process of the Double Dig, I was planning to just work the grass into the mix. After I Double Dig, I was planning to cover with plastic and leave it for all of winter. Is there anything wrong with doing it this way? It would save some work, which is important with old man winter coming around the corner.

Ah, I figured it was something like that. Thanks.

Thanks for your time and your advice Jim.

Oh, is there any kind of a generic calculation one can use for figuring how much hummus and compost I'll need? I really don't know how much to get. BTW, my book says to expect the soil to be built up about 3 inches, but it seems like adding all that hummus and compost will raise it much more than than. What do you think?

[Joe98]

I really considered this, but I don't have a truck an my schedule is bad for setting up a delivery time. I agree that a tiller is probably the way to go, but I think I'll actually enjoy doing it myself. Oh, and I ended up using cheap brick to boarder the garden because all the wood I found was treated with chemicals I wouldn't want to go into my vegetables. It's been a bit of a chore getting the brick to look right on the slight slope the garden will go on and I hate to mess it all up with a tiller I'm not familiar with.

That's for sure. lol

[Beecrofter]

Unless you are running the tiller about an inch deep to destroy weeds between the rows it's a real good idea not to till unless you are tilling organic material into the soil. Once you dig the trench with the tiller and remove the first foot of soil till all your organic material into the clayey subsoil and return the first foot to where it was. A good way to use shredded leaves and grass clippings.

[Philip Edward Lewis]

Well, you have an area for your garden, say it's 10' x 20'. Multiply 10'x20'x(3inch)x(1foot/12 inch) and you get 50 cubicfeet. (ft^3)

Most garden stuff is sold in either cubic feet or cubic yards.

1 yard^3 = 3ftx3ftx3ft=27 ft^3

You might be able to get away with a little less since tilling the soil will fluff it a little.... but the more organic material the better... ;)

good luck!

[Jim W]

Personally I wouldn't use peat moss, over here certainly it is a cause for environmental concern. Its also pricy! Compost on its own should do just fine. Yes rotted manure is a source of 'compost' but its not quite the same as 'compost' if you see what I mean!

Poss but the grass may regrow.. If you turn it over as sods though its almost the same as stacking!-)

Depending on how cold you're winters get, you might consider a cover crop instead. Grazing rye or Field beans ( an agricultural cultivar of broad bean) are ideal and very hardy.

Similar thing as covering with placcy but looks nicer!-)

Dunno depends on how bad your soil is.. If you're doing a prime prep and want to do it properly I'd reckon half to 1 barrow per m2. You'll be surprised how quickly the soil resettles once the worms and soil organisms start to further break down compost.. It may be raised at first, but will soon go down. I know a guy who double digs manure into his plot 'every year'!! Not required IMO, but he does grow good veg!-) Mind you he also uses chem fertilisers. // Jim

[Janet Baraclough]

The message from "Joe98" contains these words:

Yes do, but be sure its at the bottom so it won't regrow; see below

After I Double

I'm just in the middle of doubledigging a new bed in what was lawn, like this;

Skim off three rows of turf/sod/grass by cutting it into tiles an inch or two deep with the spade, then sliding spade underneath. Put them aside on a plastic sheet, out of the way of your working area. Dig out the uncovered soil two spits deep and put it aside, not on top of the turves you just lifted. Now skim off your next three strips of turves, and as you work put each one upside down in the bottom of the hole you dug. Spread on the turves whatever soil improver you're using; don't worry much about proportions but try to spread each material evenly.I'm using seaweed, rotted horse manure, and a LOT of coarse grit because our rainfall is high and this is to become a freedraining bed for sunlovers. Dig 2 spits of soil you exposed when you skimmed off the turves, and roughly pile it into the hole on top of the upsidedown turves (it will look mountainously high, but will settle later).Keep repeating this pattern.

When you come to the end, you will end up with a hole where you just finished digging. Fill it with the first turves and first soil which you put aside.

It's hard work, so to protect your back and joints stretch and warm up beforehand and take it slowly, with plenty of rests. Make an effort to change which foot you're digging with, on each row,to even out the muscular strain.

Covering the finished bed with (black)plastic will stop weeds germinating during late autumn; but I prefer to let them germinate so I can easily hoe them off before planting the bed. Also, you really want the winter rain and frost to break up all the lumpy soil and settle the bed down.

HTH

Janet.

Isle of Arran, Scotland.

[David J Bockman]

Hi Joe,

There is a school of thought (and a very viable one) that suggests doing away with double digging *or* tilling and simply amending, amending, amending. The 'don't till' school says that tilling destroys or seriously harms existing beneficial bacteria and in general, the tilth and aeration of the soil. Also, tilling will disturb the tens of thousands of weed seeds laying dormant and waiting to be brought closer to the surface to germinate.

I have to admit, I was skeptical, but after laying down an enormous amout of organic material along two sides of my property (approximately 80 cubic yards), I'm a firm believer. About a year later the organic material had filtered down at least 10 inches, with abundant earthworms moving between the organic and hardpan clay layers as well. I used a combination of wood chips, shredded leaves, bark, whatever it was that the city in which I live dumped in my driveway.

If the project were mine, I'd lay down clear or black plastic sheeting for a few weeks/months, which would cook not only any existing weeds but also their seeds... then amend the heck out of it and perhaps lay downa green cover such as winter rye, mustard, clover, etc. In the spring you can turn under all that great green plant material and plant in your garden, amending regularly with good stuff such as pine needles, manure, inert straw, grass clippings, shredded leaves, etc.

Just my $0.02,

Dave

PS the grass doesn't die beneath snow cover because there is still a suprising about of oxygen amongst the snowpack, as well as light.

[J Kolenovsky]

And practically stops the exchanges of gases that living products produce along with the microbial activity.

[David Hill]

Double digging, A good idea if you have the time and energy. The idea is to dig 2 "Spits" in depth a "Spit" is the depth of the blade of your spade, don't worry about it being less than 1 foot. Yes you take out a trench and put the soil aside, but to make life easier, if your plot is 20 foot wide then treat it as 2 10 foot plots so put the soil next to where you take it from. dig up to the end of the plot then back down the other side. No heavy trucking of soil from one end to the other. The idea of double digging is to break and pan that may have formed, to improve the texture of the soil and to give the plant roots a greater depth of usable soil. As you dig, skim off any weeds from the top layer with about 2 Inches of soil, and work this together with any form of humus, Peat, compost, manure, other annual weeds etc and dig these into the lower spit, then the top spit is dug to cover the lower dug spit, and so on till you finish, then just replace the soil that came from the initial trench into the trench you finish with. If you are a real glutton for punishment you could even treble dig. Double digging and treble digging were quite common during Victorian times when labour was plentiful as was manure. In those days they also used a system of making "Hot beds by taking out a trench about 4ft wide and 12 to

18 inches deep then building a bed 2ft of so high of fresh stable manure, and covering it with the soil removed from the trench, this manure would heat to over 160 F then as it started cooling Glass frames were placed over the bed and veg plants were planted, the heat from the manure giving the plants bottom heat and frost protection, so that you could grow things like lettuce, cucumbers, melons and a wide range of crops out of season. This form of gardening could use up to 200 tons of manure a year. Now back to topic. Tilling (Rotavating) is useful for rapid cultivation but has the drawback of chopping up any perennial weed roots and thus spreading them , and the blades will cause the soil at the base to form a "Pan" where the blades rub along the bottom, especially if your ground is clay and is wet, or even just damp when you work it, so digging is advisable every so often. On farms where the ground is "Rotavated" the use things like sub soilers to break this pan and to help drainage.

[Jim W]

Yes, cutting out light and air would result in this. // Jim

[Joe98]

Really? How so?

Well broken down store bought manure is probably the best I can do at this time.

Okay, I'll do the best I can with it. Much of it is already overturned and burried.

Agreed, but I'm sticking with plastic for now. Cheaper and easier to work with. Maybe once I get better at gardening, I'll make the switch.

That's a good guideline, and no, I don't plan to double dig every year.

Yeah, that just doesn't make much sense to me. A big reason for gardening is to get things organically. Especially here in the states where our argricultural laws allow for far too many inorganic substances in the food. We're still ingesting stuff you folks outlawed years ago.

Thanks

[Joe98]

Excellent. Thanks for clearing things up for me and providing such a clear idea of what to do. Thanks Janet.

[Joe98]

Thanks David. I'll have to think on that. The way things are going, I might not have an opportunity to do much digging before the ground get's hard and miserable to work. Whether I till or not, I'll be sure to have black plastic on all winter.

[Joe98]

Thanks for the advice. I'll experiment with a few methods and see what works best. I liked the history lesson, but it's just me, so labour ain't so "plentiful". I'm staying away from the treble dig. ;) But, I will avoid the tiller this time around.

[David Hill]

"........Whether I till or not, I'll be sure to have black plastic on all winter. ....."

Why?

The plastic will stop the rain going into the part covered .....but it has to go somewhere so all round the sheeting you are going to double or treble the amount of water. If you cover a few weeks before you want to dig, or better, cover AFTER digging to warm the ground before planting would be a lot better. It doesn't matter if you do have weed growth of a few inches if you are going to dig it in, in fact it will be of more value than a little dead growth, and covering wont kill off perennial weeds in less than a year. Remember if you keep it covered then it wont dry out if the water has got under the sheet half as fast as uncovered ground.

[Jim W]

Peat bogs (from which much bagged garden peat is taken) are often SSSI's (Sites of special scientific interest) as they contain rare species of flora and fauna. They take a VERY long time to replace and cutting peat destroys the living top layer.

I dunno you'd be surprised how many loopholes there are in the laws even here. // Jim

[Joe98]

It's getting cold fast, so no time to put plastic on the bed first before digging. I don't plan to plant until spring at the earliest, but I was hoping to kill the weeds and grass over the winter.

It's my understanding that with Double Digging, the ground should rest at least a month, that's why I'm doing it over winter instead of wasting time next growing season. I'm sure you're right about the perenenial weeds, but at least I'll get most of it, including the grass.

I hadn't thought of that. Maybe I'll double dig, aply the plastic and just leave it be for a few weeks. I my area we don't usually have heavy now on the ground all winter, especially at the start of the season. I'll try to remove the plastic once the grass is sure to be dead